EP4677263A1

EP4677263A1 - Laser-phosphor engine with partial polarizing beam splitter and tunable color point

Info

Publication number: EP4677263A1
Application number: EP24706752.3A
Authority: EP
Inventors: Christoph Gerard August HOELEN; Martinus Petrus Joseph PEETERS; Hugo Johan Cornelissen
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2023-03-07
Filing date: 2024-02-26
Publication date: 2026-01-14
Also published as: WO2024184100A1; CN120826562A

Abstract

The invention may provide a light generating system (1000) comprising (i) one or more light generating devices (100), (ii) a first luminescent material arrangement (2100), (iii) a reflector-luminescent material arrangement (2500), (iv) central optics (900), and (v) a control system (300), wherein the reflector-luminescent material arrangement (2500) comprises a reflector (2510) and a second luminescent material arrangement (2200), wherein the reflector (2510) is configured to reflect at least part of the device light (101) received by the reflector (2510) into reflected device light (711), wherein the second luminescent material arrangement (2200) comprises a second luminescent material (220) configured to convert at least part of the device light (101) received by the second luminescent material (220) into second luminescent material light (221) having a second luminescent material light spectral power distribution, different from the first luminescent material light spectral power distribution.

Description

Laser-phosphor engine with partial polarizing beam splitter and tunable color point

FIELD OF THE INVENTION

The invention relates to a light generating system. The invention further relates to a lighting device comprising such light generating system.

BACKGROUND OF THE INVENTION

Laser-phosphor based stage lighting engines are known in the art. For instance, WO2022143318 describes a light emitting device, comprising a first light source, a second light source, a dichroic mirror, a wavelength conversion apparatus, a first light path adjusting apparatus or a second light path adjusting apparatus, and a first scattering optical system. The light mixing effect of emergent light can be improved by using the first scattering optical system. Light emitted by the first light source is all used for exciting the wavelength conversion apparatus.

CN115268191 A discloses a projection device that comprises a laser, an optical component, a first fluorescent component, a second fluorescent component and a light outlet. The laser beam emitted by the laser includes a first laser beam that passes through the optical component and is directed toward the first fluorescent component, and a second laser beam that is reflected by the optical component towards the second fluorescent component. The first fluorescent component generates first fluorescent light under the excitation of the first laser beam, and reflects the first fluorescent light to the optical component, and the optical component reflects the first fluorescent light to the light outlet. The second fluorescent component generates second fluorescent light under the excitation of a part of the second laser light and reflects the second fluorescence and another part of the second laser light towards the optical component to emit to the light outlet.

JP2020079820A discloses a projection light source device that includes a light source unit that emits light in a first wavelength range, a phosphor that is excited by light in the first wavelength range and emits light in a second wavelength range, a reflector that reflects incident light, and a splitting-combining element that splits the light in the first wavelength range emitted by the light source unit to the phosphor and to the reflector, and combines the light reflected by the reflector and the light in the second wavelength range emitted by the phosphor.

US2013/176540A discloses a light source module includes a light-emitting device, a wavelength conversion device and a polarization and color separation unit. The light-emitting device provides an excitation beam including a first portion beam having a first polarization direction. The wavelength conversion device includes a first wavelength conversion area and a polarization conversion area. When the first portion beam irradiates the first wavelength conversion area, the first portion beam is converted into a first color beam. When the first portion beam irradiates the polarization conversion area, the first polarization direction of the first portion beam is converted to a second polarization direction. The polarization and color separation unit is disposed between the wavelength conversion device and the light-emitting device, and transmits the first portion beam with the first polarization direction, and reflects the first portion beam with the second polarization direction and the first color beam to the same direction.

SUMMARY OF THE INVENTION

High brightness light sources can be used in various applications including spots, stage-lighting, headlamps, home and office lighting, and automotive lighting. For this purpose, laser-phosphor technology can be used, wherein a laser may provide laser light and a remote phosphor converts laser light into converted light. A relatively straightforward way to produce white light using lasers is to use laser light in combination to generate phosphor converted light. Laser-phosphor systems may allow generation of high brightness light and may therefore be used in projection systems, including displays such as cinema projectors and projectors for home, school, and office applications, car front lighting, search lighting, stage lighting, architectural lighting, and special lighting applications. However, such light engine may be capable to generate only a single color point as defined by the luminescent converter. Creation of a product range providing different color points may be difficult as it may require multiple unique components to be designed, qualified, produced, and kept in stock. In other cases, e.g. in RGB LCD-based projection systems, the maximum brightness may be limited by the components used, the engine volume may be large due to the many components, and the system cost may be high due to the many dedicated components. A way to combine pump light and luminescent light may be to use a polarizing beam splitter for the pump light, by which part of the light is reflected to the luminescent material and part is transmitted to a diffuser. However, in general the diffused light may to a large degree be depolarized, which may result in relatively high losses of diffused blue light at the beam combiner where it may be combined with the luminescent light into white output light. Further, there is a desire for color tunable lighting devices and/or lighting devices having a tunable correlated color temperature, while the color points are relatively close to the BBL. Yet, it appears desirable to provide such tunable lighting device which is able to provide the light with a high intensity.

Hence, it is an aspect of the invention to provide an alternative light generating system, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as an objective to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

According to a first aspect, the invention may provide a light generating system (“system”) comprising (i) one or more light generating devices, (ii) a first luminescent material arrangement, (iii) a second luminescent material arrangement, (iv) central optics, and (v) a control system. Especially, the one or more light generating devices may be configured to generate polarized device light having a controllable polarization and having a device light spectral power distribution. Further, in embodiments the one or more light generating devices comprise one or more of a laser diode and a superluminescent diode. Especially, the first luminescent material arrangement may in embodiments comprise a first luminescent material configured to convert at least part of the device light received by the first luminescent material into first luminescent material light having a first luminescent material light spectral power distribution. Further, in embodiments the second luminescent material arrangement may comprise a second luminescent material configured to convert at least part of the device light received by the second luminescent material into second luminescent material light having a second luminescent material light spectral power distribution, (especially) different from the first luminescent material light spectral power distribution. Yet, in embodiments the central optics may comprise one or more of a (i) a central optics polarizing beam splitter, and (ii) a central optics dichroic beam splitter. In embodiments, the central optics polarizing beam splitter may be configured to transmit and/or reflect at least part of the device light in dependence of its polarization. Further, in embodiments the central optics dichroic beam splitter may be configured to transmit and/or reflect at least part of the device light, at least part of the first luminescent material light, and at least part of the second luminescent material light in dependence of their (respective) spectral power distributions. Yet, in embodiments the light generating system may be configured such that at least part of the device light, when having a first polarization, may propagate from the one or more light generating devices via the central optics to the first luminescent material arrangement to provide the first luminescent material light.

Alternatively or additionally, in embodiments the light generating system may be configured such that at least part of the device light, when having a second polarization, different from the first polarization, may propagate from the one or more light generating devices via the central optics to the second luminescent material arrangement to provide the second luminescent material light. Yet, alternatively or additionally, in embodiments the light generating system may be configured such that at least part of the first luminescent material light generated by the first luminescent material arrangement, and at least part of the second luminescent material light generated by the second luminescent material arrangement, may escape from the light generating system via the central optics. Further, in embodiments the control system may be configured to control the polarization of the device light. Yet, especially the light generating system may be configured to generate system light comprising one or more of the device light, the first luminescent material light, and the second luminescent material light. Yet, in an aspect the invention may provide light generating system (“system”) comprising (i) one or more light generating devices, (ii) a first luminescent material arrangement, (iii) a reflector-luminescent material arrangement, (iv) central optics, and (v) a control system. Especially, the one or more light generating devices may be configured to generate polarized device light having a controllable polarization and having a device light spectral power distribution. In specific embodiments, the one or more light generating devices comprise one or more of a laser diode and a superluminescent diode. Yet, in embodiments the first luminescent material arrangement may comprise a first luminescent material configured to convert at least part of the device light received by the first luminescent material into first luminescent material light having a first luminescent material light spectral power distribution. Further, in embodiments the reflector-luminescent material arrangement may comprise a reflector and a second luminescent material arrangement. Especially, in embodiments the reflector may be configured to reflect at least part of the device light received by the reflector into reflected device light. Yet, especially the second luminescent material arrangement may in embodiments comprise a second luminescent material configured to convert at least part of the device light received by the second luminescent material into second luminescent material light having a second luminescent material light spectral power distribution, (especially) different from the first luminescent material light spectral power distribution. Further, in embodiments the central optics may comprise (i) a central optics polarizing beam splitter, and (ii) a central optics dichroic beam splitter. In specific embodiments, the central optics polarizing beam splitter may be configured to transmit and/or reflect at least part of the device light in dependence of its polarization. Yet, in embodiments the central optics dichroic beam splitter may be configured to transmit and/or reflect at least part of the device light, at least part of the first luminescent material light, and at least part of the second luminescent material light in dependence of their (respective) spectral power distributions. Especially, in embodiments the light generating system may be configured such that at least part of the device light, when having a first polarization, may propagate from the one or more light generating devices via the central optics to the first luminescent material arrangement to provide the first luminescent material light. Further, especially in embodiments the light generating system may be configured such that at least part of the device light, when having a second polarization, different from the first polarization, may propagate from the one or more light generating devices via the central optics to the reflector-luminescent material arrangement to provide the second luminescent material light and the reflected device light. Yet, in embodiments the light generating system may be configured such that at least part of the first luminescent material light generated by the first luminescent material arrangement, at least part of the second luminescent material light generated by the second luminescent material arrangement, and at least part of the reflected device light generated at the reflector, may escape from the light generating system via the central optics. In embodiments, the control system may be configured to control the polarization of the device light. Further, in specific embodiments the light generating system may be configured to generate system light comprising one or more of the first luminescent material light, the reflected device light, and the second luminescent material light (especially wherein the system may comprise one or more of (i) the first luminescent material light and (ii) the reflected device light and the second luminescent material light). Therefore, the invention may provide in specific embodiments a light generating system comprising (i) one or more light generating devices, (ii) a first luminescent material arrangement, (iii) a reflector-luminescent material arrangement, (iv) central optics, and (v) a control system, wherein: (A) the one or more light generating devices are configured to generate polarized device light having a controllable polarization and having a device light spectral power distribution; wherein the one or more light generating devices comprise one or more of a laser diode and a superluminescent diode; (B) the first luminescent material arrangement comprises a first luminescent material configured to convert at least part of the device light received by the first luminescent material into first luminescent material light having a first luminescent material light spectral power distribution; (C) the reflector-luminescent material arrangement comprises a reflector and a second luminescent material arrangement; (D) the reflector is configured to reflect at least part of the device light received by the reflector into reflected device light; (E) the second luminescent material arrangement comprises a second luminescent material configured to convert at least part of the device light received by the second luminescent material into second luminescent material light having a second luminescent material light spectral power distribution, different from the first luminescent material light spectral power distribution; (F) the central optics comprises (i) a central optics polarizing beam splitter, and (ii) a central optics dichroic beam splitter; wherein: (Fl) the central optics polarizing beam splitter is configured to transmit and/or reflect at least part of the device light in dependence of its polarization; and (F2) the central optics dichroic beam splitter is configured to transmit and/or reflect at least part of the device light, at least part of the first luminescent material light, and at least part of the second luminescent material light in dependence of their (respective) spectral power distributions; (G) the light generating system is configured such that (a) at least part of the device light, when having a first polarization, propagates from the one or more light generating devices via the central optics to the first luminescent material arrangement to provide the first luminescent material light, (b) at least part of the device light, when having a second polarization, different from the first polarization, propagates from the one or more light generating devices via the central optics to the reflector-luminescent material arrangement to provide the second luminescent material light and the reflected device light, and (c) at least part of the first luminescent material light generated by the first luminescent material arrangement, at least part of the second luminescent material light generated by the second luminescent material arrangement, and at least part of the reflected device light generated at the reflector, escape from the light generating system via the central optics; (H) the control system is configured to control the polarization of the device light; and (I) the light generating system is configured to generate system light comprising one or more of the first luminescent material light, the reflected device light, and the second luminescent material light (especially one or more of (i) the first luminescent material light and (ii) the reflected device light and the second luminescent material light).

With such system, a high power light generating system may be provided. Further, such system may allow control of spectral power distribution of the system light (of a high power system). Yet, such system may in a safe way provide high power light. The system may be relatively compact. Yet, thermal management of the luminescent material may also be provided with this system. In addition to high optical power, the system may also provide high radiance (or luminance), i.e., a high optical power density of the source. The system may be more fail-safe thanks to the reflective configuration for both the luminescent light and the diffused light, by which it can be prevented that direct laser beams emit from the system in case the luminescent component or the diffusing component would fail (e.g. break, fall off, etc.). Especially, the tunable beam combining laser phosphor engine may comprise central optics having at least a polarizing beam splitter function and dichroic beam splitter function. Therefore, amongst others in embodiments a laser phosphor engine with partial polarizing beam splitter and tunable color point with reduced offset from BBL may be provided.

As indicated above, the light generating system may in embodiments comprise (i) one or more light generating devices, (ii) a first luminescent material arrangement, (iii) a reflector-luminescent material arrangement, (iv) central optics, and (v) a control system.

The light generating system may comprise one or more light generating devices. Especially, the one or more light generating devices may be configured to generate polarized device light having a controllable polarization and having a device light spectral power distribution. As will be further elucidated below, the controllable polarization may be obtained by one or more of (a) a controllable polarizer, and (b) two or more light generating devices configured to generate device light having different polarizations, respectively. Further, the spectral power distribution of the device light, indicates as “device light spectral power distribution” may in embodiments especially be in the blue wavelength range, see also below. The phrase “device light spectral power distribution”, and similar phrases, may indicate the spectral power distribution of the device light. Yet, as further described below, in embodiments the one or more light generating devices comprise one or more solid state light sources. More especially, the one or more light generating devices may comprise one or more of a laser diode and a superluminescent diode. Hence, the light generating device may comprise one or more laser diodes and/or one or more superluminescent diodes. Here below, some general aspects in relation to the one or more light generating devices is described.

A light generating device may especially be configured to generate device light. Especially, the light generating device may comprise a light source. The light source may especially configured to generate light source light. In embodiments, the device light may essentially consist of the light source light. In other embodiments, the device light may essentially consist of converted light source light. In yet other embodiments, the device light may comprise (unconverted) light source light and converted light source light. Light source light may be converted with a luminescent material into luminescent material light and/or with an upconverter into upconverted light (see also below). The term “light generating device” may also refer to a plurality of light generating devices which may provide device light having essentially the same spectral power distributions. In (other) specific embodiments, the term “light generating device” may also refer to a plurality of light generating devices which may provide device light having different spectral power distributions. The term “light source” may in principle relate to any light source known in the art. It may be a conventional (tungsten) light bulb, a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, an LED (light emissive diode). In a specific embodiment, the light source comprises a solid state LED light source (such as an LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of light sources, such as 2-2000 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chip-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi LED chip configured together as a single lighting module.

The term “light source” may also refer to a chip scaled package (CSP). A CSP may comprise a single solid state die with provided thereon a luminescent material comprising layer. The term “light source” may also refer to a midpower package. A midpower package may comprise one or more solid state die(s). The die(s) may be covered by a luminescent material comprising layer. The die dimensions may be equal to or smaller than 2 mm, such as in the range of e.g. 0.2-2 mm. Hence, in embodiments the light source comprises a solid state light source. Further, in specific embodiments, the light source comprises a chip scale packaged LED. Herein, the term “light source” may also especially refer to a small solid state light source, such as having a mini size or micro size. For instance, the light sources may comprise one or more of mini LEDs and micro LEDs. Especially, in embodiment the light sources comprise micro LEDs or “microLEDs” or “pLEDs”. Herein, the term mini size or mini LED especially indicates to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm - 1 mm. Herein, the term p size or micro LED especially indicates to solid state light sources having dimensions, such as die dimension, especially length and width, selected from the range of 100 pm and smaller. The light source may have a light escape surface. Referring to conventional light sources such as light bulbs or fluorescent lamps, it may be an outer surface of a glass or a quartz envelope. For LED’s it may for instance be the LED die, or when a resin may be applied to the LED die, the outer surface of the resin. In principle, it may also be the terminal end of a fiber. The term escape surface especially relates to that part of the light source, where the light actually leaves or escapes from the light source. The light source is configured to provide a beam of light. This beam of light (thus) escapes from the light exit surface of the light source.

Likewise, a light generating device may comprise a light escape surface, such as an end window. Further, likewise a light generating system may comprise a light escape surface, such as an end window.

A position where system light escapes from the light generating system may also be indicated as light exit. This may be a light transmissive window or an opening (in the system). The light transmissive window may in embodiments be provided by an optical component.

The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a laser diode, a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser (EEL), a photonic crystal surface emitting laser (PCSEL), a vertical external cavity surface emitting laser (VECSEL), etc... The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid-state light source (such as an LED or laser diode). In an embodiment, the light source comprises an LED (light emitting diode). The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED). The term LED may also refer to a plurality of LEDs. The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 solid state light sources. In embodiments, the light source may comprise one or more micro- optical elements (array of micro lenses) downstream of a single solid-state light source, such as an LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise an LED with on-chip optics. In embodiments, the light source comprises pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering).

In embodiments, the light source may be configured to provide primary radiation, which is used as such, such as e.g. a blue light source, like a blue LED, or a green light source, such as a green LED, and a red light source, such as a red LED. Such LEDs, which may not comprise a luminescent material (“phosphor”) may be indicated as direct color LEDs. In other embodiments, however, the light source may be configured to provide primary radiation and part of the primary radiation may be converted into secondary radiation. Secondary radiation may be based on conversion by a luminescent material. The secondary radiation may therefore also be indicated as luminescent material radiation. The luminescent material may in embodiments be comprised by the light source, such as an LED with a luminescent material layer or dome comprising luminescent material. Such LEDs may be indicated as phosphor converted LEDs or PC LEDs (phosphor converted LEDs). In other embodiments, the luminescent material may be configured at some distance (“remote”) from the light source, such as an LED with a luminescent material layer not in physical contact with a die of the LED. Hence, in specific embodiments the light source may be a light source that during operation emits at least light at wavelength selected from the range of 380-470 nm. However, other wavelengths may also be possible. This light may partially be converted by the luminescent material. In embodiments, the light generating device may (thus) comprise a luminescent material. In embodiments, the light generating device may comprise a PC LED. In other embodiments, the light generating device may comprise a direct LED (i.e. no phosphor). In embodiments, the light generating device may comprise a laser device, like a laser diode. In embodiments, the light generating device may comprise a superluminescent diode. Hence, in specific embodiments, the light source may be selected from the group of laser diodes and superluminescent diodes. In other embodiments, the light source may comprise an LED.

The light source may especially be configured to generate light source light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light source light may in embodiments comprise one or more bands, having band widths as known for lasers. The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid state light source as such, like a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source (but may also be indicated as light generating device). Hence, a white LED is a light source (but may e.g. also be indicated as (white) light generating device). The term “light source” herein may also refer to a light source comprising a solid state light source, such as an LED or a laser diode or a superluminescent diode. The term “light source” may (thus) in embodiments also refer to a light source that is (also) based on conversion of light, such as a light source in combination with a luminescent converter material. Hence, the term “light source” may also refer to a combination of an LED with a luminescent material configured to convert at least part of the LED radiation, or to a combination of a (diode) laser with a luminescent material configured to convert at least part of the (diode) laser radiation.

In embodiments, the term “light source” may also refer to a combination of a light source, like an LED, and an optical filter, which may change the spectral power distribution of the light generated by the light source. Especially, the term “light generating device” may be used to address a light source and further (optical components), like an optical filter and/or a beam shaping element, etc.

The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin.

The term “solid state light source”, or “solid state material light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, or a superluminescent diode. The term “laser light source” especially refers to a laser. Such laser may especially be configured to generate laser light source light having one or more wavelengths in the UV, visible, or infrared, especially having a wavelength selected from the spectral wavelength range of 200-2000 nm, such as 300-1500 nm. The term “laser” especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, refer to a laser diode (or diode laser).

Hence, in embodiments the light source comprises a laser light source. In embodiments, the terms “laser” or “solid state laser” or “solid state material laser” may refer to one or more of cerium doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), chromium doped chrysoberyl (alexandrite) laser, chromium ZnSe (CrZnSe) laser, divalent samarium doped calcium fluoride (Sm:CaF2) laser, Er:YAG laser, erbium doped and erbium-ytterbium codoped glass lasers, F-Center laser, holmium YAG (Ho: YAG) laser, Nd:YAG laser, NdCrYAG laser, neodymium doped yttrium calcium oxoborate Nd:YCa4O(BO3)3 or Nd:YCOB, neodymium doped yttrium orthovanadate (Nd:YVO4) laser, neodymium glass (Nd:glass) laser, neodymium YLF (Nd:YLF) solid-state laser, promethium 147 doped phosphate glass (147Pm³⁺:glass) solid-state laser, ruby laser (AhO3:Cr³⁺), thulium YAG (Tm:YAG) laser, titanium sapphire (Ti:sapphire; AhO3:Ti³⁺) laser, trival ent uranium doped calcium fluoride (U:CaF2) solid-state laser, Ytterbium doped glass laser (rod, plate/chip, and fiber), Ytterbium YAG (Yb:YAG) laser, Yb2O3 (glass or ceramics) laser, etc.

For instance, including second and third harmonic generation embodiments, the light source may comprise one or more of an F center laser, an yttrium orthovanadate (Nd:YVO4) laser, a promethium 147 doped phosphate glass (147Pm³⁺:glass), and a titanium sapphire (Ti:sapphire; AhO3:Ti³⁺) laser. For instance, considering second and third harmonic generation, such light sources may be used to generated blue light.

In embodiments, the terms “laser” or “solid state laser” or “solid state material laser” may refer to one or more of a semiconductor laser diodes, such as GaN, InGaN, AlGalnP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc.

A laser may be combined with an upconverter in order to arrive at shorter (laser) wavelengths. For instance, with some (trival ent) rare earth ions upconversion may be obtained or with non-linear crystals upconversion can be obtained. Alternatively, a laser can be combined with a downconverter, such as a dye laser, to arrive at longer (laser) wavelengths.

As can be derived from the below, the term “laser light source” may also refer to a plurality of (different or identical) laser light sources. In specific embodiments, the term “laser light source” may refer to a plurality N of (identical) laser light sources. In embodiments, N=2, or more. In specific embodiments, N may be at least 5, such as especially at least 8. In this way, a higher brightness may be obtained. In embodiments, laser light sources may be arranged in a laser bank (see also above). The laser bank may in embodiments comprise heat sinking and/or optics e.g. a lens to collimate the laser light. Hence, in embodiments lasers in a laser bank (or “laser array bank”) may share the same optics.

The laser light source is configured to generate laser light source light (or “laser light”). The light source light may essentially consist of the laser light source light. The light source light may also comprise laser light source light of two or more (different or identical) laser light sources. For instance, the laser light source light of two or more (different or identical) laser light sources may be coupled into a light guide, to provide a single beam of light comprising the laser light source light of the two or more (different or identical) laser light sources. In specific embodiments, the light source light is thus especially collimated light source light. In yet further embodiments, the light source light is especially (collimated) laser light source light.

The laser light source light may in embodiments comprise one or more bands, having band widths as known for lasers. In specific embodiments, the band(s) may be relatively sharp line(s), such as having full width half maximum (FWHM) in the range of less than 20 nm at RT, such as equal to or less than 10 nm. Hence, the light source light has a spectral power distribution (intensity on an energy scale as function of the wavelength) which may comprise one or more (narrow) bands.

The beams (of light source light) may be focused or collimated beams of (laser) light source light. The term “focused” may especially refer to converging to a small spot. This small spot may be at the discrete converter region, or (slightly) upstream thereof or (slightly) downstream thereof. Especially, focusing and/or collimation may be such that the cross-sectional shape (perpendicular to the optical axis) of the beam at the discrete converter region (at the side face) is essentially not larger than the cross-section shape (perpendicular to the optical axis) of the discrete converter region (where the light source light irradiates the discrete converter region). Focusing may be executed with one or more optics, like (focusing) lenses. Especially, two lenses may be applied to focus the laser light source light. Collimation may be executed with one or more (other) optics, like collimation elements, such as lenses and/or parabolic mirrors. In embodiments, the beam of (laser) light source light may be relatively highly collimated, such as in embodiments <2° (FWHM), more especially <1° (FWHM), most especially <0.5° (FWHM). Hence, <2° (FWHM) may be considered (highly) collimated light source light. Optics may be used to provide (high) collimation (see also above).

The term “solid state material laser”, and similar terms, may refer to a solid state laser like based on a crystalline or glass body dopes with ions, like transition metal ions and/or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, such as e.g. a vertical cavity surface-emitting laser (VCSEL), etc. The term “solid state light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a laser diode, or a superluminescent diode. Instead of the term “solid state light source” also the term “semiconductorbased light source” may be applied. Hence, the term “semiconductor-based light source” may e.g. refer to one or more of a light emitting diode (LED), a laser diode, and a superluminescent diode. Hence, the light generating device may comprise one or more of a light emitting diode (LED), a laser diode, and a superluminescent diode.

A light-emitting diode (LED) is especially a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor may recombine with electron holes, releasing energy in the form of photons. The color of the light (corresponding to the energy of the photons) may be determined by the energy required for electrons to cross the band gap of the semiconductor. A laser diode (or diode laser) may be a semiconductor device substantially similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction. This is known to a person skilled in the art.

Superluminescent diodes are known in the art. A superluminescent diode may be indicated as a semiconductor device which may be able to emit low-coherence light of a broad spectrum like an LED, while having a brightness in the order of a laser diode. US2020192017 indicates for instance that “With current technology, a single SLED is capable of emitting over a bandwidth of, for example, at most 50-70 nm in the 800-900 nm wavelength range with sufficient spectral flatness and sufficient output power. In the visible range used for display applications, i.e. in the 450-650 nm wavelength range, a single SLED is capable of emitting over bandwidth of at most 10-30 nm with current technology. Those emission bandwidths are too small for a display or projector application which requires red (640 nm), green (520 nm) and blue (450 nm), i.e. RGB, emission" . Further, superluminescent diodes are amongst others described, in “Edge Emitting Laser Diodes and Superluminescent Diodes”, Szymon Stanczyk, Anna Kafar, Dario Schiavon, Stephen Naj da, Thomas Slight, Piotr Perlin, Book Editor(s): Fabrizio Roccaforte, Mike Leszczynski, First published: 03 August 2020 https://doi.org/10.1002/9783527825264.ch9 in chapter 9,3 superluminescent diodes. This book, and especially chapter 9.3, are herein incorporated by reference. Amongst others, it is indicated therein that the superluminescent diode (SLD) is an emitter, which combines the features of laser diodes and light-emitting diodes. SLD emitters utilize the stimulated emission, which means that these devices operate at current densities similar to those of laser diodes. The main difference between LDs and SLDs is that in the latter case, the device waveguide may be designed in a special way preventing the formation of a standing wave and lasing. Still, the presence of the waveguide ensures the emission of a high- quality light beam with high spatial coherence of the light, but the light is characterized by low time coherence at the same time” and “Currently, the most successful designs of nitride SLD are bent, curved, or tilted waveguide geometries as well as tilted facet geometries, whereas in all cases, the front end of the waveguide meets the device facet in an inclined way, as shown in Figure 9.10. The inclined waveguide suppresses the reflection of light from the facet to the waveguide by directing it outside to the lossy unpumped area of the device chip". Hence, an SLD may especially be a semiconductor light source, where the spontaneous emission light is amplified by stimulated emission in the active region of the device. Such emission is called “super luminescence”. Superluminescent diodes combine the high power and brightness of laser diodes with the low coherence of conventional lightemitting diodes. The low (temporal) coherence of the source has advantages that the speckle is significantly reduced or not visible, and the spectral distribution of emission is much broader compared to laser diodes, which can be better suited for lighting applications. Especially, with varying electrical current, the spectral power distribution of the superluminescent diode may vary. In this way the spectral power distribution can be controlled, see e.g. also Abdullah A. Alatawi, et al., Optics Express Vol. 26, Issue 20, pp. 26355-26364, https://doi.org/10.1364/QE.26.026355. Hence, a superluminescent diode may be indicated as a semiconductor device which may be able to emit low-coherence light of a broad spectrum like a LED, while having a brightness in the order of a laser diode. Superluminescent diodes may combine the high power and brightness of laser diodes with the low coherence of conventional light-emitting diodes. The low (temporal) coherence of the source has advantages that the speckle is significantly reduced or not visible, and the spectral distribution of emission is much broader compared to laser diodes, which can be better suited for lighting applications. Hence, in embodiments, the solid state light source may comprise a superluminescent diode. For instance, in further specific embodiments, the solid state light source may comprise a GaN-based superluminescent diode, or an InGaN-based superluminescent diode, or an AlGaN-based superluminescent diode.

Especially, in embodiments the light generating device is configured to generate device light. In specific embodiments, the device light may be blue light. The terms “blue light” or “blue emission”, and similar terms, may especially relate to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues). However, intensity at shorter wavelengths may also be possible, such as within the wavelength range of 400-440 nm. In specific embodiments, the device light may have a centroid wavelength (Xci) selected from the 400-490 nm wavelength range, more especially from the 400-480 nm wavelength range. Especially, in embodiments the device light has a peak wavelength selected from the blue wavelength range.

In embodiments, the device light may be unpolarized light. Further, in (other) embodiments the device light may comprise one or more of polarized light having a p polarization and polarized light having an s polarization. Hence, in specific embodiments the device light may be elliptically polarized. Optionally, the polarization of the device light may be controllable, such as using one or more of (i) polarization control optics, and (ii) using two or more light generating devices generating device light having different (linear or elliptical) polarizations. Embodiments will further be described below.

In embodiments, the light generating device comprises a light source selected from a laser diode and a superluminescent diode. Hence, especially the light generating device comprises a solid state light source. More especially, the device light is laser light.

Further, the light generating system comprises a first luminescent material arrangement comprising a first luminescent material. The first luminescent material arrangement may at least comprise the first luminescent material, but may in embodiments comprise one or more other elements (for instance a rotatable element, a heat sink, a reflector, one or more lenses, etc.). Especially, the first luminescent material may be configured to convert at least part of the device light received by the first luminescent material into first luminescent material light having a first luminescent material light spectral power distribution.

The phrase “... light received by ...”, and similar phrases, such as “device light received by the first luminescent material” may especially indicate that when the light is actually received by an item, an action may take place. Whether the light is received by the item, may e.g. depend upon the operational mode of the system. For instance, dependent upon the polarization of the light and/or the spectral power distribution of the light, the light may be irradiate the item, upon which the action may take place. The action may in embodiments be one or more of conversion, reflection, and transmission. Hence, the action may also include refraction. The phrase “to convert at least part of the device light received by the first luminescent material into first luminescent material light” may thus indicate that when at least part of device light indeed irradiates the first luminescent material (in an operational mode of the light generating system), then at least part of that device light may be converted into first luminescent material light. Whether the device light may reach the first luminescent material may depend upon the polarization of the device light. Especially, the first luminescent material may be operated in the reflective mode, though a transmissive mode may also be possible (see further also below).

The first luminescent material light may have a spectral power distribution with at least intensity in the visible wavelength range, see further also below.

Here below, some general aspects in relation to luminescent materials are described, which may apply to both the first luminescent material and the second luminescent material (see further below).

The term “luminescent material” especially refers to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the second radiation has a spectral power distribution at larger wavelengths than the first radiation, which is the case in the so- called down-conversion. In specific embodiments, however the second radiation has a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up-conversion. In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and/or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation and blue radiation, into visible light. The luminescent material may in specific embodiments also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. In general, the luminescent material will be a down converter, i.e. radiation of a smaller wavelength is converted into radiation with a larger wavelength (UuUm), though in specific embodiments the luminescent material may comprise up-converter luminescent material, i.e. radiation of a larger wavelength is converted into radiation with a smaller wavelength ( x> m).

In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and/or fluorescence. The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. Instead of the term “luminescent material” also the term “phosphor” may be applied. These terms are known to the person skilled in the art.

In embodiments, luminescent materials are selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc. Alternatively or additionally, the luminescent material(s) may be selected from silicates, especially doped with divalent europium.

In specific embodiments the luminescent material comprises a luminescent material of the type AsBsOn Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. Embodiments of garnets especially include A3B5O12 garnets, wherein A comprises at least yttrium or lutetium and wherein B comprises at least aluminum. Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. Especially, B may comprise aluminum (Al); however, in addition to aluminum, B may also partly comprise gallium (Ga) and/or scandium (Sc) and/or indium (In), especially up to about 20% of B, more especially up to about 10 % of B (i.e. the B ions essentially consist of 90 or more mole % of Al and 10 or less mole % of one or more of Ga, Sc and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and/or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Yi-_xLu_x)3B50i2:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Yi-_xLu_x)3A150i2:Ce, part of Y and/or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Yo.iLuo.89Ceo.oi)3A150i2. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art. In embodiments, the luminescent material (thus) comprises A3B5O12 wherein in specific embodiments at maximum 10% of B-0 may be replaced by Si-N.

In specific embodiments the luminescent material comprises (Y_xiA’_X2Ce_X3)3(AlyiB’y2)₅Oi2, wherein xl+x2+x3=l, wherein x3>0, wherein 0<x2+x3<0.2, wherein yl+y2=l, wherein especially 0<y2<0.2, wherein A’ comprises one or more elements selected from the group consisting of lanthanides, and wherein B’ comprises one or more elements selected from the group consisting of Ga, In and Sc. In embodiments, x3 is selected from the range of 0.001-0.1. In the present invention, especially xl>0, such as >0.2, like at least 0.8. Garnets with Y may provide suitable spectral power distributions.

In specific embodiments at maximum 10% of B-0 may be replaced by Si-N. Here, B in B-0 refers to one or more of Al, Ga, In and Sc (and O refers to oxygen); in specific embodiments B-0 may refer to Al-O. As indicated above, in specific embodiments x3 may be selected from the range of 0.001-0.04. Especially, such luminescent materials may have a suitable spectral distribution (see however below), have a relatively high efficiency, have a relatively high thermal stability, and allow a high CRI (optionally in combination with (the) light of other sources of light as described herein). Hence, in specific embodiments A may be selected from the group consisting of Lu and Gd. Alternatively or additionally, B may comprise Ga. Hence, in embodiments the luminescent material comprises (Y_xi(Lu,Gd)_X2Ce_X3)3(AlyiGa_y2)5Oi2, wherein Lu and/or Gd may be available. Even more especially, x3 is selected from the range of 0.001-0.1, wherein 0<x2+x3<0.1, and wherein 0<y2<0.1. Further, in specific embodiments, at maximum 1% of B-0 may be replaced by Si- N. Here, the percentage refers to moles (as known in the art); see e.g. also EP3149108. In yet further specific embodiments, the luminescent material comprises (Y_xiCe_X3)3A150i2, wherein xl+x3=l, and wherein 0<x3<0.2, such as 0.001-0.1.

In specific embodiments, the light generating device may only include luminescent materials selected from the type of cerium comprising garnets. In even further specific embodiments, the light generating device includes a single type of luminescent materials, such as (Y_xiA’_X2Ce_X3)3(Al_yiB’_y2)5Oi2. Hence, in specific embodiments the light generating device comprises luminescent material, wherein at least 85 weight%, even more especially at least about 90 wt.%, such as yet even more especially at least about 95 weight % of the luminescent material comprises (Y_xiA’_X2Ce_X3)3(Al_yiB’_y2)5Oi2. Here, wherein A’ comprises one or more elements selected from the group consisting of lanthanides, and wherein B’ comprises one or more elements selected from the group consisting of Ga, In and Sc, wherein xl+x2+x3=l, wherein x3>0, wherein 0<x2+x3<0.2, wherein yl+y2=l, wherein 0<y2<0.2. Especially, x3 is selected from the range of 0.001-0.1. Note that in embodiments x2=0. Alternatively or additionally, in embodiments y2=0.

In specific embodiments, A may especially comprise at least Y, and B may especially comprise at least Al.

Alternatively or additionally, the luminescent material may comprise a luminescent material of the type AsSieNiuCe³ , wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y.

In embodiments, the luminescent material may alternatively or additionally comprise one or more of MS:Eu²⁺ and/or LSisNs Eu² and/or MAlSiNs Eu² and/or Ca2AlSi3O2Ns:Eu²⁺, etc., wherein M comprises one or more of Ba, Sr, and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2SisN8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu²⁺). For instance, assuming 2% Eu in CaAlSi Eu, the correct formula could be (Cao.98Euo.o2)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr or Ba. The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Further, the material (Ba,Sr,Ca)2SisN8:Eu can also be indicated as NfcSis Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not taking into account the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Bai.sSro.sSis Eu (i.e. 75 % Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca). Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSi Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.

In embodiments, a red luminescent material may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2SisN8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu²⁺). For instance, assuming 2% Eu in CaAlSi Eu, the correct formula could be (Cao.98Euo.o2)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr, or Ba.

The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca).

Further, the material (Ba,Sr,Ca)2SisN8:Eu can also be indicated as NESis Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not taking into account the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Bai.sSro.sSis Eu (i.e. 75 % Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca).

Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSi Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca).

Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.

Blue luminescent materials may comprise YSO (Y2SiOs:Ce³⁺), or similar compounds, or BAM (BaMgAlioOi?:Eu²⁺), or similar compounds. The term “luminescent material” herein especially relates to inorganic luminescent materials.

Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and/or organic dyes may be applied and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc. etc.

Quantum dots are small crystals of semiconducting material generally having a width or diameter of only a few nanometers. When excited by incident light, a quantum dot emits light of a color determined by the size and material of the crystal. Light of a particular color can therefore be produced by adapting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with a shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium free quantum dots such as indium phosphide (InP), and copper indium sulfide (CuInS?) and/or silver indium sulfide (AglnS?) can also be used. Quantum dots show very narrow emission band and thus they show saturated colors. Furthermore the emission color can easily be tuned by adapting the size of the quantum dots. Any type of quantum dot known in the art may be used in the present invention. However, it may be preferred for reasons of environmental safety and concern to use cadmium-free quantum dots or at least quantum dots having a very low cadmium content.

Instead of quantum dots or in addition to quantum dots, also other quantum confinement structures may be used. The term “quantum confinement structures” should, in the context of the present application, be understood as e.g. quantum wells, quantum dots, quantum rods, tripods, tetrapods, or nanowires, etcetera.

Organic phosphors can be used as well. Examples of suitable organic phosphor materials are organic luminescent materials based on perylene derivatives, for example compounds sold under the name Lumogen® by BASF. Examples of suitable compounds include, but are not limited to, Lumogen® Red F305, Lumogen® Orange F240, Lumogen® Yellow F083, and Lumogen® F170.

Different luminescent materials may have different spectral power distributions of the respective luminescent material light. Alternatively or additionally, such different luminescent materials may especially have different color points (or dominant wavelengths).

As indicated above, other luminescent materials may also be possible. Hence, in specific embodiments the luminescent material is selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures. Quantum structures may e.g. comprise quantum dots or quantum rods (or other quantum type particles) (see above). Quantum structures may also comprise quantum wells. Quantum structures may also comprise photonic crystals.

In embodiments, the luminescent material may at least comprise a luminescent material of the type AsBsOn Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc.

In specific embodiments, the luminescent material may comprise at least two different luminescent materials configured to provide luminescent material light having different spectral power distributions. As can be derived from the above, the term “different luminescent materials” may refer to luminescent materials that are different, or to two compositions, each including at least one luminescent material in common, but wherein the compositions differ. For instance, a first luminescent material comprising luminescent materials A and B, and a second luminescent material comprising only A or only B, or comprising both A and B, but in a different weight ratio. Such first luminescent material and second luminescent material may have different spectral power distributions of their respective luminescent material light.

Further examples of luminescent materials are described below in relation to the second luminescent material.

The luminescent material may be configured in the system such that, optionally together with optics, device light may reach the luminescent material, though this may depend (also) on the polarization of the device light.

In embodiments, the luminescent material may have an excitation band, especially in the blue wavelength range, at least partly overlapping with a device light emission band. This may apply to essentially any luminescent material used herein, though embodiments wherein one luminescent material is excited by the emission of another luminescent material are not excluded.

Especially, the system may also comprises a second luminescent material. Especially, the second luminescent material may be configured to convert at least part of the device light received by the second luminescent material into second luminescent material light having a second luminescent material light spectral power distribution. The phrase “to convert at least part of the device light received by the second luminescent material into second luminescent material light” may thus indicate that when at least part of device light indeed irradiates the second luminescent material (in an operational mode of the light generating system), then at least part of that device light may be converted into second luminescent material light. Whether the device light may reach the second luminescent material may depend upon the polarization of the device light.

In embodiments, the second luminescent material may be operated in the reflective mode. In other embodiments, however, the second luminescent material may be operated in a transmissive mode (see further also below).

In embodiments, the second luminescent material light spectral power distribution may be different from the first luminescent material light spectral power distribution (and also different from the device light). Hence, none of the first spectral power distribution and the spectral power distribution may fully overlap the other. Especially, the color points may differ. Hence, in embodiments also the centroid wavelengths may differ. Hence, the first luminescent material light, the second luminescent material light, and the device light may have mutually different spectral power distributions.

In specific embodiments, colors or color points of a first type of light and a second type of light may be different when the respective color points of the first type of light and the second type of light differ with at least 0.01 for u’ and/or with at least 0.01 for v’, even more especially at least 0.02 for u’ and/or with at least 0.02 for v’. In yet more specific embodiments, the respective color points of first type of light and the second type of light may differ with at least 0.03 for u’ and/or with at least 0.03 for v’. Here, u’ and v’ are color coordinates of the light in the CIE 1976 UCS (uniform chromaticity scale) diagram. Spectral power distributions of different sources of light having centroid wavelengths differing at least 10 nm, such as at least 20 nm, or even at least 30 nm may be considered different spectral power distributions, e.g. different colors. In general, the differences in centroid wavelengths will not be larger than about 400 nm, such as not more than 350 nm.

In embodiments, wherein the device light has a device light centroid wavelength X^a, the first luminescent material light has a first luminescent material light centroid wavelength Xci, and the second luminescent material light has a second luminescent material light centroid wavelength A-2, especially (X«d+5 nm)< Xc2<(X<;i-5 nm), more especially (Xcd+10 nm)< Xc2<(X<;i-10 nm). Yet, in embodiments wherein (X«d+15 nm)< c2<(Xci-50 nm). Further, in embodiments the device light centroid wavelength Ad may be selected from the wavelength range of 400-480 nm. Alternatively or additionally, in embodiments the first luminescent material light centroid wavelength Xci may be selected from the wavelength range of 490-780 nm. Yet alternatively or additionally, in embodiments the second luminescent material light centroid wavelength A-2 may be selected from the wavelength range of 450-520 nm. Hence, the device light may in embodiments especially be selected from the violet-blue wavelength range. For instance, at least 80% of the spectral power distribution of the device light may be in the violet-blue wavelength range. Further, the first luminescent material light may essentially have intensity in the entire visible wavelength range above about 450 nm. For instance, at least 80% of the spectral power distribution of the first luminescent material light may be in the wavelength range of 450-780 nm. However, especially any luminescent material that may qualify as first luminescent material may provide (first) luminescent material light having a first centroid wavelength larger than the second centroid wavelength of (second) luminescent material light of any luminescent material that may qualify as second luminescent material. As indicated above, in embodiments Xc2<(X<;i-10 nm), more especially Xc2<(X<;i-50 nm). The first luminescent material light may (thus) in embodiments emit in the green-red wavelength range. The second luminescent material may emit in about the blue-cyan wavelength range, especially in the 450-520 nm wavelength range. For instance, at least 80% of the spectral power distribution of the second luminescent material light may be in the wavelength range of 450- 520 nm. Even though the wavelength range for the second luminescent material light may overlap with the wavelength range for the second luminescent material light, the luminescent materials may especially be selected such that there may be no full overlap. For that reason, the centroid wavelengths are also chosen differently. The first luminescent material light may have a centroid wavelength that is (substantially) larger than the second luminescent material light. Further, in embodiments (%d+20 nm)< %2, or even (Xcd+20 nm)< . For instance, the device light may be blue light, the second luminescent material light may be cyan light, and the first luminescent material may consist of one or more of green light, yellow light, orang light, and red light.

Herein, the terms “violet light” or “violet emission”, and similar terms, may especially relate to light having a wavelength in the range of about 380-440 nm. In specific embodiments, the violet light may have a centroid wavelength in the 380-440 nm range. The terms “green light” or “green emission”, and similar terms, may especially relate to light having a wavelength in the range of about 490-560 nm. In specific embodiments, the green light may have a centroid wavelength in the 490-560 nm range. The terms “yellow light” or “yellow emission”, and similar terms, may especially relate to light having a wavelength in the range of about 560-590 nm. In specific embodiments, the yellow light may have a centroid wavelength in the 560-590 nm range. The terms “orange light” or “orange emission”, and similar terms, may especially relate to light having a wavelength in the range of about 590-620 nm. In specific embodiments, the orange light may have a centroid wavelength in the 590-620 nm range. The terms “red light” or “red emission”, and similar terms, may especially relate to light having a wavelength in the range of about 620-750 nm. In specific embodiments, the red light may have a centroid wavelength in the 620-750 nm range. The terms “cyan light” or “cyan emission”, and similar terms, especially relate to light having a wavelength in the range of about 490-520 nm. In specific embodiments, the cyan light may have a centroid wavelength in the 490-520 nm range. The terms “amber light” or “amber emission”, and similar terms, may especially relate to light having a wavelength in the range of about 585-605 nm, such as about 590-600 nm. In specific embodiments, the amber light may have a centroid wavelength in the 585-605 nm range. The phrase “light having one or more wavelengths in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least intensity or intensities at these one or more wavelengths in the indicate wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at one or more wavelengths in the 440-495 nm wavelength range. Here, the term “green-red wavelength range” may especially refer to the entire wavelength range green and red, and all wavelengths in between, i.e. 490-780 nm. Especially, the luminescent material may have a centroid wavelength selected from the green-red wavelength range.

In specific embodiments, the first luminescent material may at least comprise a luminescent material of the type AsBsOn Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc. Alternatively or additionally, in embodiments the second luminescent material may at least comprise one or more of Nao.sKo.sLisSiO^Eu² , MSi2O2N2: Eu²⁺, wherein M comprises one or more of Ba, Sr, and Ca (especially wherein M at least comprises Sr), Sr[BeeON4]:Eu²⁺, and MAhO^Eu² , wherein M comprises one or more of Ba, Sr, and Ca (especially wherein M at least comprises Sr). In embodiments, the second luminescent material may comprise MBe6-_y-zMg_yAl_zOi- _ZN4+_Z:RE, wherein M comprises one or more of Ba, Sr, and Ca (especially wherein M at least comprises Sr), and wherein RE comprises one or more of Eu²⁺ and Ce³⁺, and wherein 0 < y < 2 ; 0 < z< 1, of which Sr[BeeON4]:Eu²⁺ is an example.

The second luminescent material may be comprised by a second luminescent material arrangement. The second luminescent material arrangement may at least comprise the second luminescent material, but may in embodiments comprise one or more other elements (for instance a rotatable element, a heat sink, a reflector, one or more lenses, etc.).

Especially, in embodiments the system may comprise a reflector-luminescent material arrangement. In embodiments, the reflector-luminescent material arrangement may comprise a reflector and a second luminescent material arrangement. Especially, device light received by the reflector-luminescent material arrangement may be received by both the reflector and a second luminescent material arrangement. Hence, part of the device light received by the reflector-luminescent material arrangement may be received by the reflector and part of the device light received by the reflector-luminescent material arrangement may be received by the second luminescent material arrangement. Especially, the reflector may be configured to reflect at least part of the device light received by the reflector into reflected device light. Hence, at least part of the device light received by the reflector-luminescent material arrangement may be converted into the second luminescent material light and at least part of the device light received by the reflector-luminescent material arrangement may be converted into the reflected device light. The reflector may especially be a diffuse reflector (see further also below).

Further, the system may comprise optics, as indicated above, and also further elucidated below. Especially, the system at least comprises central optics. In embodiments, the central optics may comprise (i) a central optics polarizing beam splitter, and (ii) a central optics dichroic beam splitter.

In embodiments, the central optics polarizing beam splitter may be configured to transmit and/or reflect at least part of the device light in dependence of its polarization. Especially, for device light with one of the polarizations (like p or s) may apply that its transmission by the central optics polarizing beam splitter is higher than the transmission for device light having another polarization (like s or p), whereas also for device light with the one of the polarizations (like p or s) may apply that its reflection by the central optics polarizing beam splitter is lower than the reflection for device light having another polarization (like s or p) (see further also below).

Especially, the central optics polarizing beam splitter may be selected such that the first luminescent material light and/or the second luminescent material light are substantially transmitted. Note that the first luminescent material light and/or the second luminescent material light may be substantially unpolarized light.

In embodiments, the central optics dichroic beam splitter may be configured to transmit and/or reflect at least part of the device light, at least part of the first luminescent material light, and at least part of the second luminescent material light in dependence of their (respective) spectral power distributions.

Especially, for the first luminescent material light and second luminescent material may apply that either (a) the transmission of the first luminescent material light at the central optics dichroic beam splitter is higher than its reflection at the central optics dichroic beam splitter, and the reflection of the second luminescent material light at the central optics dichroic beam splitter is higher than its transmission at the central optics dichroic beam splitter, or (b) the transmission of the first luminescent material light at the central optics dichroic beam splitter is lower than its reflection at the central optics dichroic beam splitter, and the reflection of the second luminescent material light at the central optics dichroic beam splitter is lower than its transmission at the central optics dichroic beam splitter.

The term “central optics” may be applied as essentially all light, i.e. the reflected device light, the first luminescent material light, and the second luminescent material light may only escape from the system via the central optics. Further, the device light may only reach the reflector, the first luminescent material and the second luminescent material via the central optics. Hence, the term “central optics polarizing beam splitter” refers to a polarizing beam splitter comprised by the central optics. Likewise, the term “central optics dichroic beam splitter” refers to a dichroic beam splitter comprised by the central optics.

In embodiments, the light generating system may be configured such that at least part of the device light, when having a first polarization (such as p or s), may propagate from the one or more light generating devices via the central optics to the first luminescent material arrangement to provide the first luminescent material light. Alternatively or additionally in embodiments, the light generating system may be configured such that at least part of the device light, when having a second polarization (such as s or p), (i.e. thus) different from the first polarization, may propagate from the one or more light generating devices via the central optics to the reflector-luminescent material arrangement to provide the second luminescent material light and the reflected device light. Yet alternatively or additionally in embodiments, the light generating system may be configured such that at least part of the first luminescent material light generated by the first luminescent material arrangement, at least part of the second luminescent material light generated by the second luminescent material arrangement, and at least part of the reflected device light generated at the reflector, escape from the light generating system via the central optics.

The above, such as especially the phrase “at least part of the first luminescent material light generated by the first luminescent material arrangement, at least part of the second luminescent material light generated by the second luminescent material arrangement, and at least part of the reflected device light generated at the reflector, escape from the light generating system via the central optics” does not necessarily imply that at the same time first luminescent material light, second luminescent material light, and reflected device light escape from the system. Whether or not first luminescent material light and second luminescent material light (and reflected device light) are generated may depend upon the polarization of the device light. By controlling its polarization, the device light may be distributed over different routes (within the system), one to the first luminescent material arrangement, and/or another one to the second luminescent material arrangement (and to the reflector).

Therefore, especially the control system may be configured to control the polarization of the device light (see further also below).

Hence, in specific embodiments, the central optics polarizing beam splitter may be configured to transmit and/or reflect at least part of the device light in dependence of its polarization. Further, in specific embodiments the central optics dichroic beam splitter may be configured to (a) to transmit or reflect at least part of the first luminescent material light, (b) to reflect or transmit at least part of the second luminescent material light, and (c) to reflect or transmit at least part of the reflected device light. Especially, the central optics polarizing beam splitter, and the central optics dichroic beam splitter are configured such that at least part of the first luminescent material, at least part of the second luminescent material light, and at least part of the reflected device light reaching the central optics, may escape from the system in essentially the same directions. Especially, this may imply that one of (a) the first luminescent material light and (b) the reflected device light and the second luminescent material light is transmitted by the central optics and the other one of (a) the first luminescent material light and (b) the reflected device light and the second luminescent material light is reflected by the central optics. Hence, the system may especially be configured such that first luminescent material light propagating to the central optics on the one hand, and reflected device light and second luminescent material light propagating to the central optics on the other hand have a mutual angle of (about) 90°.

In specific embodiments, the central optics dichroic beam splitter is designed for 45° angle of incidence of the device light. Examples of such dichroic beam splitter are e.g. a short-pass cut-off dichroic plate, or a long-pass cut-off dichroic plate.

Yet, in specific embodiments, the central optics polarizing beam splitter is designed for 45° angle of incidence of the device light.

Hence, the central optics may comprise at least two different functionalities, which may e.g. be realized by using two optical components, or by using a single optical component with two different functional layers (or sets of layers)(e.g. surface configurations or coatings / dichroic layer stacks; or by integration of both functions in a single surface layer or coating (stack of dichroic layers)). Therefore, in embodiments, the central optics may comprise a single optical component having polarizing beam splitting functionality and dichroic beam splitting functionality, or comprises two optical components, one having polarizing beam splitting functionality and one having dichroic beam splitting functionality.

In embodiments the light generating system may be configured to generate system light comprising one or more of the first luminescent material light, the reflected device light, and the second luminescent material light. As the device light may, dependent upon its polarization, propagate in embodiments to the reflector-luminescent arrangement, the generation of second luminescent material light and reflected device light may be dependent in the same way on the polarization of the device light. Therefore, in embodiments the light generating system may be configured to generate system light comprising one or more of (i) the first luminescent material light and (ii) the reflected device light and the second luminescent material light.

Especially, herein the reflector may comprise a diffuse reflector. Further, the reflector is thus especially operated in the reflective mode. Alternative to a diffuse reflector, a transmissive diffusor may be applied. This embodiment is herein further not described.

Hence, in embodiments the reflector may be configured to diffuse at least part of the device light received by the reflector thereby providing diffused reflected device light. More especially, the reflector may be configured to diffuse at least part of the device light received by the reflector thereby providing diffused reflected device light while maintaining at least part of the polarization of the device light. Hence, the reflector may be a diffuser element operated in the reflective mode. Further, in embodiments the reflector may also be indicated as “diffuser element”. Especially, in embodiments at least part of the polarization may be maintained. An example of such diffuser element is a metallic coated glass diffuser showing 95-98% reflectance.

In specific embodiments, a polarization changing element may be configured between the central optics and the reflector (especially the diffuser element). Especially, the polarization changing element may be configured to change s-polarized light or p-polarized light to circular polarized light. The reflector may change the direction of the polarized light, but the circular polarized light may essentially stay circular polarized light. However, it may change from left to right, or from right to left polarized light at the reflector. At least part of the diffused light, having circular polarization, will propagate from the reflector to the polarization changing element, and then be converted to (diffused) s-polarized light and/or (diffused) p-polarized light, which may further propagate to the central optics. Therefore, in embodiments the polarization changing element may comprise a X/4 waveplate. In embodiments, the system may (thus) comprise a polarization changing element, wherein the polarization changing element is especially configured in an optical path of the device light between the central optics and the reflector. In this way, p-polarized light can be converted in diffused s-polarized light, and s-polarized light can be converted in diffused p-polarized light. Especially, the polarization changing element may be an element that induces a 90° phase shift between the two orthogonal linear polarization components (s and p) of the light. The most common way is to use birefringent material (birefringent rotators), such as a quarterwave plate. An alternative may be to use the Faraday effect, in which case the phase shift is caused by an applied magnetic field (Faraday rotators).

With respect to the reflector-luminescent material arrangement, several options may be possible.

In embodiments, the reflector and the second luminescent material may be configured adjacent to each other. At least part of the device light that propagates in the direction of the reflector-luminescent material arrangement may be received by both the reflector and the second luminescent material (i.e. part may be received by the reflector and part may be received by the second luminescent material).

The reflector may comprise one or more reflector parts and/or the second luminescent may be configured in one or more second luminescent material parts. Hence, the reflector and luminescent material may be configured in a ID or 2D array of reflector parts second luminescent material parts. Therefore, in embodiments the reflector-luminescent material arrangement comprises an array of alternating reflectors and second luminescent material areas comprising the second luminescent material. At least part of the device light that propagates in the direction of the reflector-luminescent material arrangement may be received by a plurality of reflectors and by a plurality of and second luminescent material areas (i.e. part may be received by a plurality of reflectors and part may be received by a plurality of and second luminescent material areas). The dimensions, such as length, width, or diameter of the alternating reflectors and second luminescent material areas may be selected from the range of about 0.01-1 mm, such as 0.05-0.5 mm.

In embodiments, the second luminescent material may be configured on the reflector, with the second luminescent material at least partly being transmissive for the device light that reaches the luminescent material and/or the second luminescent comprising openings. Therefore, in embodiments the second luminescent material may be configured on at least part of the reflector, wherein one or more of the following may apply: (i) the luminescent material only partly covers the reflector, and (ii) the luminescent material is (also) configured to transmit part of the device light received by the luminescent material.

In embodiments, the reflector may comprise one or more reflector parts and/or the second luminescent may be comprised by one or more second luminescent material parts, The one or more reflector parts and the one or more second luminescent material parts may be comprised by a rotatable element. By rotating the rotatable element, the device may (alternatingly) irradiate the reflector (parts) and the second luminescent material (parts). In embodiments, the luminescent material and the reflector may be in different tracks, adjacent to each other (i.e. having different radii), allowing simultaneous generation of the reflected device light and second luminescent material light. In embodiments, the luminescent material and the reflector may be configured alternating along essentially the same radius of the rotatable element, allowing alternating generation of the reflected device light and second luminescent material light. When the rotational frequency is at least about 40 Hz, such as at least about 50 Hz, then the human eye may not see the sequential generation. An actuator may be used to control the rotatable element.

Likewise, the first luminescent material may be comprised by a rotatable element. An (other) actuator may be used to control the rotatable element comprising the first luminescent material.

Note that in specific embodiments the first luminescent material, the second luminescent material, and the reflector may be configured on the same rotatable element.

Here some general aspects in relation to the rotatable element are described, which may in embodiments apply to the first luminescent material and/or the second luminescent material.

With high power irradiation of the luminescent material, the thermal load may become critical. Hence, in embodiments the luminescent material may be configured to extend in a circular configuration, such as on a disc, and may be rotated during operation of the system. In this way, the luminescent material is only temporarily heated, and is allowed to cool during a (short) time before it is again irradiated. Hence, in embodiments the system may comprise a rotatable element, wherein the rotatable element comprises the luminescent material; wherein during operation of the light generating system (in the first operational mode) the rotatable element rotates, such that over time different parts of the luminescent material are irradiated by the device light. Likewise, this may apply to the diffuser element. Hence, in embodiments the system may comprise a rotatable element, wherein the rotatable element comprises the diffuser element; wherein during operation of the light generating system (in the first operational mode) the rotatable element rotates, such that over time different parts of the diffuser element are irradiated by the second device light. Rotational frequencies may e.g. be selected from the range of 40-300 Hz, though other rotational frequencies may also be possible. Hence, typically, the duration of irradiating the luminescent material is much shorter (> lOx, more commonly > 50x) than the duration of not irradiating the luminescent material. In embodiments, the rotatable element may be provided as wheel or disc. Hence, in embodiments the rotatable element may comprise a phosphor wheel. However, rotating rods may also be applied.

Especially, the embodiments with the rotatable element may be combined. Hence, the system may comprise a rotatable element, wherein the rotatable element comprises the luminescent material; wherein during operation of the light generating system (in an operational mode) the rotatable element rotates, such that over time different parts of the luminescent material are irradiated by the device light. Yet, in specific embodiments the rotatable element also comprises the diffuser element, spatially separated from the luminescent material; wherein during operation of the light generating system (in an operational mode) the rotatable element rotates, such that over time different parts of the diffuser element are irradiated by the device light.

Hence, the system may further comprise an actuator configured to rotate the rotatable element. The control system may control the actuator (and thereby the rotational frequency).

Hence, in embodiments the system may comprise a rotatable element, wherein the rotatable element comprises the first luminescent material; wherein in an operational mode of the light generating system the rotatable element rotates, such that over time different parts of the first luminescent material are irradiated by the device light, and/or the system may comprise a rotatable element, wherein the rotatable element comprises the second luminescent material; wherein in an operational mode of the light generating system the rotatable element rotates, such that over time different parts of the second luminescent material are irradiated by the device light.

Further, in embodiments the luminescent material may be configured in thermal contact with a thermally conductive material. For instance, the luminescent material may be configured in thermal contact with a thermally conductive element. A thermally conductive element may especially comprise thermally conductive material. A thermally conductive material may especially have a thermal conductivity of at least about 20 W/(m*K), like at least about 30 W/(m*K), such as at least about 100 W/(m*K), like especially at least about 200 W/(m*K). In yet further specific embodiments, a thermally conductive material may especially have a thermal conductivity of at least about 10 W/(m*K). In embodiments, the thermally conductive material may comprise one or more of copper, aluminum, silver, gold, silicon carbide, aluminum nitride, boron nitride, aluminum silicon carbide, beryllium oxide, a silicon carbide composite, aluminum silicon carbide, a copper tungsten alloy, a copper molybdenum carbide, carbon, diamond, and graphite. Alternatively, or additionally, the thermally conductive material may comprise or consist of aluminum oxide. In embodiments, the thermally conductive element may comprise one or more of a heatsink, a heat spreader, and a two-phase cooling device. In yet other embodiments, the thermally conductive element may be configured in thermal contact with one or more of a heatsink, a heat spreader, and a two-phase cooling device, and may e.g. transfer heat to such heatsink, heat spreader, or two-phase cooling device, via another thermally conductive element.

An element may be considered in “thermal contact” with another element if it can exchange energy through the process of heat. Hence, the elements may be thermally coupled. In embodiments, thermal contact can be achieved by physical contact. In embodiments, thermal contact may be achieved via a thermally conductive material, such as a thermally conductive glue (or thermally conductive adhesive). Thermal contact may also be achieved between two elements when the two elements are arranged relative to each other at a distance of equal to or less than about 10 pm, though larger distances, such as up to 100 pm may be possible. The shorter the distance, the better the thermal contact. Especially, the distance is 10 pm or less, such as 5 pm or less, such as 1 pm or less. The distance may be the distanced between two respective surfaces of the respective elements. The distance may be an average distance. For instance, the two elements may be in physical contact at one or more, such as a plurality of positions, but at one or more, especially a plurality of other positions, the elements are not in physical contact. For instance, this may be the case when one or both elements have a rough surface. Hence, in embodiments in average the distance between the two elements may be 10 pm or less (though larger average distances may be possible, such as up to 100 pm). In embodiments, the two surfaces of the two elements may be kept at a distance with one or more distance holders. When two elements are in thermal contact, they may be in physical contact or may be configured at a short distance of each other, like at maximum 10 pm, such as at maximum 1 mm. When the two elements are configured at a distance from each other, an intermediate material may be configured in between, though in other embodiments, the distance between the two elements may filled with a gas, liquid, or may be vacuum. When an intermediate material is available, the larger the distance, the higher the thermal conductivity may be useful for thermal contact between the two elements. However, the smaller the distance, the lower the thermal conductivity of the intermediate material may be (of course, higher thermal conductive materials may also be used).

As indicated above, the propagation of the device light within the system may depend upon its polarization. To control the polarization, several options may be possible. In embodiments, a polarization control element may be applied, which may control the polarization of the device light. In other embodiments, two or more light generating devices may be applied, which are configured to provide device light having different polarizations, respectively. By controlling the two or more light generating devices, the polarization of the device light may be controlled.

The light generating system further comprises a polarization control element, wherein the polarization control element is configured to control polarization of the device light received by the polarization control element. In embodiments, the polarization changing element comprises a X/2 waveplate. The polarization control element is configured between at least one of the light generating devices and the central optics. The control system is configured to control the polarization control element. Hence, in this way the polarization of the device light may be controllable.

Therefore, downstream of the light generating device, the polarization control may be configured. With the polarization control element, the polarization of the device light may be controlled. For instance, with a (rotatable) X/2 retarder (see also below), in embodiments polarizations between fully s polarization and fully p polarization may be chosen. In this way, the ratio between the device light that is directed via the central optics to the first luminescent material arrangement and device light that is directed via the central optics to the second luminescent material arrangement may be controlled. Note that in embodiments in some operational modes, essentially all device light may be directed via the central optics to the first luminescent material arrangement. In embodiments, in some other operational modes, essentially all device light may be directed via the central optics to second luminescent material arrangement. Yet, in embodiments in other operational modes, part of the device light may be directed via the central optics to first luminescent material arrangement and part of the device light may be directed via the central optics to the second luminescent material arrangement. Hence, (a) the polarization control element may be used to control the ratio of the polarizations of the device light, and (downstream thereof) the central optics routes, dependent upon the polarization of the device light, the further propagation of the device light (see further also below).

Hence, in embodiments the polarization control element may especially be configured to control polarization of the device light. In embodiments, the polarization control element may especially be configured to control a degree of polarization of the polarized light.

Especially, in embodiments the degree of polarization may be defined as a percentage of the p-polarized light or the s-polarized light relative to the total of s-polarized light and p-polarized light. For determining the percentages, the angular luminance of the device light having s polarization and the angular luminance of the device light having p polarization may be applied. For instance, the device light, downstream of the polarization control element, may have 20% s polarization and 80% p polarization. For the angular luminance, see e.g. Blom, S. et al., Towards a polarized light-emitting backlight: Microstructured anisotropic layers, DOI- 10.1889/1.1827869, Journal of the Society for Information Display, September 2002, p. 209-213. Instead of the angular luminance, also the luminance may be applied.

Yet, (in general) the term “degree of polarization” is known in the art. Especially, in embodiments the degree of polarization may be defined as a percentage of the p-polarized light and/or the s-polarized light relative to the total of p-polarized light and s- polarized light. Measurement of the degree of polarization is known in the art, and may be based on Stokes parameters.

In embodiments, by rotating the polarization control element the polarization of the device light may be controlled. As indicated herein, especially the device light, upstream of the polarization control element, may be linearly polarized, like s-polarized or p- polarized. Optionally, the device light may be a combination of s-polarized light and p- polarized light. For instance, with the polarization control element (by rotation the polarization control element), the combination of polarization control element and second source may provide device light, downstream of the polarization control element, having at least two polarizations selected from: essentially p-polarized, essentially s-polarized, and a combination of p-polarized and s-polarized. Note that in embodiments by rotating the polarization control element, a ratio between p-polarized and s-polarized may be controlled. For instance, would the device light be p-polarized light, by rotating the polarization control element, the contribution of p-polarized light may be reduced and the contribution of s- polarized may be increased, until essentially s-polarized light is obtained. Hence, in dependence of the rotational angle, the polarization of the device light may be controlled. In embodiments, a degree of polarization of the device light may be controlled by the polarization control element. The system may comprise an actuator configured to control the polarization control element. The control system may control the actuator for controlling the polarization control element. In embodiments, the afore-mentioned angle may be fixed during operation (i.e. not controllable during operation), and in other embodiments, this angle may be controlled (by the control system). Especially, herein the polarization of the device light propagating to the central optics is controllable (with the polarization control element). Especially, rotation of the polarization control element may imply rotation of the rotator axis. As further indicated below, the polarization control element may comprise a birefringent rotator.

Hence, in embodiments, the polarization control element may comprise a rotatable birefringent rotator. More especially, the (rotatable) birefringent rotator comprises a X/2 waveplate. However, other phase-shift inducing components for the two linear orthogonal polarization components which can change the ratio of transmitted versus reflected light may also be applied. With a half-wavelength plate, s-polarized light can be transformed for 0- 100% into p-polarized light. With a quarter-wavelength plate that may be only 0-50%. With a 3/8th-wavelength plate 0-75%, and with a l/8th-wavelength plate 0-25%. So, a halfwavelength plate may give full flexibility (and independence of the actual polarization direction of the source), while the other options may give more limitations, both in terms of the fraction of light that can be transformed into required polarized components and in terms of the orientation of the polarization direction of the source.

In specific embodiments, the polarization control element may be configured fixed. In such embodiments, essentially only a (single) first operational mode may be available, unless other parameters are variable (like the radiant flux of the first device light, and/or the radiant flux of the second device light (see below)). In other embodiments, the polarization control element may be configured controllable, especially rotatable. In such embodiments, by rotating the polarization control element, the spectral power distribution of the system light may be controlled. In such embodiments, a plurality of first operational modes may be available, with different spectral power distributions. Especially, instead of the term “s-polarized light”, and similar terms, also the term “linear s-polarized light” may be applied. Further, especially, instead of the term “p- polarized light”, and similar terms, also the term “linear p-polarized light” may be applied.

Alternatively or additionally, in embodiments the one or more light generating devices may comprise two different types of light generating devices, differing in the type of polarization of the device light they generate; wherein the light generating system further comprises a first polarizing beam splitter, wherein the first polarizing beam splitter is configured downstream of the two different types of light generating devices and upstream of the central optics; and wherein the first polarizing beam splitter is configured to transmit (at least part of the) s-polarized light or p-polarized light, and to reflect (at least part of the) p- polarized light or (at least part of the) s-polarized light. Especially, the control system may be configured to control the two different types of light generating devices.

In order to further increase input power and/or to provide a further control options, more than one type of light generating device may be applied, wherein at least two types differ in the polarized light they provide. For instance, in embodiments one of the types may e.g. have primarily s-polarized light, and another one of the types may e.g. have primarily p-polarized light. A polarizing beam splitter may be used to combine the beams of the two types of light generating devices. Hence, the term light generating device may also refer to one or more primary light generating device and one or more secondary light generating devices. Therefore, in embodiments the system may comprise a primary light generating device and a secondary light generating device, wherein the device light of one of the primary light generating device and the secondary light generating device, comprises more s-polarized than the other one of the primary light generating device and the secondary light generating device, wherein the light generating system further comprises second optics, configured downstream of the primary light generating device and the secondary light generating device, and configured upstream of the first optics, wherein the second optics comprises a first polarizing beam splitter, wherein the first polarizing beam splitter is configured to transmit (at least part of the) s-polarized light or p-polarized light, and to reflect (at least part of the) p-polarized light or (at least part of the) s-polarized light. For instance, in embodiments the device light of the other one of the primary light generating device and the secondary light generating device, comprises more p-polarized than the one of the primary light generating device and the secondary light generating device.

In embodiments, the first polarizing beam splitter may be configured to reflect at least 80% of (first) device light, having a first polarization, of a first type of light generating devices, and transmit at least 80% of (second) device light, having a second polarization, of a second type of light generating devices. Especially, the first device light and second device light may thus have - in embodiments - different polarizations (and optionally also different spectral power distributions), like having first device light having s polarization or p polarization, and the second device light having p polarization or s polarization (i.e. the polarization chosen different from the first polarization). More especially, in embodiments the first polarizing beam splitter may be configured to reflect at least 90% of (first) device light, having a first polarization, of a first type of light generating devices, and transmit at least 90% of (second) device light, having a second polarization, of a second type of light generating devices. Percentages may be based on energy (Watt).

One or more primary light generating devices, especially a plurality of primary light generating device, may be configured in a laser bank, wherein the primary light generating devices comprise laser diodes. Alternatively or additionally, one or more secondary light generating devices, especially a plurality of secondary light generating device may be configured in a laser bank, wherein the secondary light generating devices comprise laser diodes. The laser banks may be different laser banks, though a configuration in the same laser bank may also be possible.

Alternatively or additionally, in order to further increase input power and/or to provide a further control options, more than one type of light generating device may be applied, wherein at least two types differ in the spectral power distribution they provide. One of the types may have a different wavelength than the other one, such as a different peak wavelengths, and a dichroic beam splitter may be used to combine the beams of the two types of light generating devices. When using a (simple) cut-on or cut-off dichroic pass filter, in combination with a PBS e.g. up to four light source beams may be combined within the same etendue (i.e., may be projected within the same spot and angular range on the phosphor). Especially, for the type of light generating devices having device light with the largest peak wavelength this largest peak wavelength is the first peak wavelength as described herein. Any further type of light generating device may generate first device light have the same peak wavelength or a peak wavelength at smaller wavelengths. Further, for all types of light generating devices may the conditions apply as described herein in relation to the light generating device.

Therefore, in (other) embodiments, the one or more light generating devices may comprise two different types of light generating devices, differing in a spectral power distribution of the device light they generate, wherein the light generating system may further comprises a first dichroic beam splitter, wherein the first dichroic beam splitter may be configured downstream of the two different types of light generating devices and upstream of the central optics, wherein the first dichroic beam splitter may be configured (a) to transmit or reflect at least part of the device light of a first type, and (b) to reflect or transmit at least part of the device light of a second type. Especially, the control system may be configured to control the two different types of light generating devices.

In embodiments, the first dichroic beam splitter may be configured to reflect at least 80% of (first) device light of a first type of light generating devices, and transmit at least 80% of (second) device light of a second type of light generating devices. Especially, the first device light and second device light may thus have - in embodiments - different spectral power distributions (and optionally also different polarizations), like having centroid wavelengths differing at least 10 nm, such as at least about 15 nm. More especially, in embodiments the first dichroic beam splitter may be configured to reflect at least 90% of (first) device light of a first type of light generating devices, and transmit at least 90% of (second) device light of a second type of light generating devices. Percentages may be based on energy (Watt).

The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”.

Hence, in embodiments the one or more light generating devices may comprise a first light generating device and a second light generating device. The first light generating device may be configured to generate first device light having a first centroid wavelength. The second light generating device may be configured to generate second device light having a second centroid wavelength. Especially, both the first centroid wavelength and the second centroid wavelength may be is selected from the wavelength range of 400-480 nm. In specific embodiments, the first device light may be blue light. Yet, in specific embodiments, the second device light may be blue light.

Especially, the first device light may have a first peak wavelength I. In specific embodiments, the first peak wavelength XI is selected from the blue wavelength range. Further, especially, the second device light has a second peak wavelength X2. In specific embodiments, the second peak wavelength X2 is selected from the blue wavelength range.

In embodiments the first device light may comprise one or more of polarized light having a p polarization and polarized light having an s polarization. Hence, in embodiments the first device light may be elliptically polarized. Optionally, the polarization of the first device light may be controllable, such as using one or more of (i) polarization control optics, and (ii) using two or more first light generating devices generating device light having different (linear or elliptical) polarizations. However, as indicated below, the polarization may especially (also) be controlled by the polarization control element. In embodiments, the first light generating device comprises a first light source selected from a laser diode and a superluminescent diode. Hence, especially the first light generating device comprises a solid state light source. More especially, the first device light is laser light. Herein, especially the first device light comprises-polarized light, whereas the first device light may comprise polarized light. Hence, the first device light as generated by the first light generating device may especially have a net polarization.

In embodiments the second device light may comprise one or more of polarized light having a p polarization and polarized light having an s polarization. Hence, in embodiments the second device light may be elliptically polarized. Optionally, the polarization of the second device light may be controllable, such as using one or more of (i) polarization control optics, and (ii) using two or more second light generating devices generating device light having different (linear or elliptical) polarizations. However, as indicated below, the polarization may especially (also) be controlled by the polarization control element. In embodiments, the second light generating device comprises a second light source selected from a laser diode and a superluminescent diode. Hence, especially the second light generating device comprises a solid state light source. More especially, the second device light is laser light. Herein, especially the second device light comprises- polarized light, whereas the first device light may comprise polarized light. Hence, the second device light as generated by the second light generating device may especially have a net polarization.

In embodiments, | XI- 2| > 3 nm, such as | XI- 2| > 4 nm |, more especially XI- 2| > 5 nm. More especially, | XI- 2| > 10 nm, or even | I- X2| > 15 nm. Yet, in embodiments 10 nm < | XI- X2| < 50 nm. In specific embodiments, the first peak wavelength may be selected at a spectral position of maximum absorption of the luminescent material, and the second peak wavelength thus at a position of at least 5 nm, more especially at least 10 nm, blue shifted or red shift, especially red shifted. Hence, in embodiments X2> 1. This may be useful in view of the use of the dichroic beam splitter used in the central optics (see also below). In other embodiments, the first peak wavelength may and the second peak wavelength may both be selected at a spectral position offset from maximum absorption of the luminescent material. For instance, one may be a blue shifted relative to the maximum absorption and the other one may be red shifted relative to the maximum absorption.

Assuming the use of laser, the difference between first peak wavelength and the second peak wavelength may be relatively small. Especially, the first peak wavelength and the second peak wavelength, and the first optics, may be selected such that the two peak wavelengths are spectrally positioned at two opposite sides of a cut-on / cut-off wavelength of a dichroic filter comprised by the first optics. Hence, the first peak wavelength and the second peak wavelength, and the first optics may be selected such, that the first optics may spectrally separate them, and essentially transmit one and essentially reflect the other.

Hence, the first device light and second device light may have different spectral power distributions and/or different color points.. Note that for the first device light and the second device light, the differences in centroid wavelengths may be relatively small, such as selected from the range of 3-50 nm, such as selected from the range of 5-50 nm, like selected from the range of 5-40 nm. Hence, in embodiments the difference in centroid wavelength of the first device light and second device light herein may in embodiments be not larger than about 50 nm.

When using two or more different types of light generating devices differing in spectral power distribution of the respective device light, the polarizations of the respective device light may be the same. With the polarization control element, the polarization can be controlled (see also above). However, as indicated above, in other embodiments two or more different types of light generating devices differing in respective polarizations of the device light (and not necessarily also differing in spectral power distribution of the respective device light) may be applied. Then, a polarization control element is not necessarily used, as the via power control, the polarization of the device light can be controlled. However, it is of course also possible to use two or more different light generating devices, with device light differing in spectral power distribution and polarization. Optionally, a polarization control element may be applied.

Here below, some further embodiments in relation to the central optics are described. Especially, in embodiments, device light reaching the central optics may be reflected and/or transmitted by the central optics polarizing beam splitter. Especially, (a) the polarization of the device light and (b) the central optics polarizing beam splitter may be configured such that (i) at least part of the device light propagates to the first luminescent material arrangement, and (ii) at least part of the first luminescent material light may escape from the system via the central optics. Alternatively or additionally, especially, (a) the polarization of the device light and (b) the central optics polarizing beam splitter may be configured such that (i) at least part of the device light propagates to the reflector- luminescent material arrangement, and (ii) at least part of the second luminescent material light and at least part of the diffused device light may escape from the system via the central optics. This may e.g. imply that the central optics polarizing beam splitter may at least partially be transmissive for a first polarization and at least partially reflective for a second polarization, or, the other way around, this may e.g. imply that the central optics polarizing beam splitter is at least partially transmissive for a second polarization and at least partially transmissive for a second polarization.

As indicated above, the system may especially be configured such that diffused device light propagating to the central optics and first luminescent material light propagating to the central optics have a mutual angle of (about) 90°. Hence, in embodiments first luminescent material light reaching the central optics may be reflected or transmitted at the central optics dichroic beam splitter. The central optics dichroic beam splitter may be configured such that (a) diffused device light may be reflected at the central optics dichroic beam splitter when the central optics dichroic beam splitter is configured to transmit the first luminescent material light, and/or (b) diffused device light may be transmitted at the central optics dichroic beam splitter when the central optics dichroic beam splitter is configured to reflect the first luminescent material light. Therefore, in embodiments the system may especially be configured such that diffused device light and first luminescent material light propagating orthogonal to the central optics may escape (in the same direction) from the system via the central optics to provide system light comprising the diffused device light and first luminescent material light. System light may escape from a light exit of the system (see also above).

Especially, (a) the centroid wavelength and/or peak wavelength of the device light, and the centroid wavelength of the second luminescent material light and (b) the centroid wavelength of the first luminescent material may be selected such that the peak wavelength and/or centroid wavelength of the device light and the centroid wavelength of the second luminescent material light on the one hand and the centroid wavelength of the first luminescent material light on the other hand are spectrally positioned at two opposite sides of a cut-on / cut-off wavelength of a dichroic filter comprised by the central optics. Hence, the peak wavelength and/or centroid wavelength of the device light, as well as the centroid wavelength of the second luminescent material light on the one hand, and the centroid wavelength of the first luminescent material on the other hand, may be selected such, that the central optics dichroic beam splitter may spectrally substantially separate them, and essentially transmit one and essentially reflect the other.

Further, in embodiments, the central optics dichroic beam splitter may be configured (a) to transmit or reflect at least 70% of the device light received by the central optics dichroic beam splitter, more especially at least 80%, such as at least 90% (like even at least about 95%). Alternatively or additionally, the central optics dichroic beam splitter may be configured (b) to reflect or transmit at least 70% of the first luminescent material light received by the central optics dichroic beam splitter, more especially at least 80%, such as at least 90% (like even at least about 95%). Yet, in embodiments, the central optics dichroic beam splitter may be configured (c) to transmit or reflect at least 70% of the reflected device light and second luminescent material light received by the central optics dichroic beam splitter, more especially at least 80%, such as at least 90%. Note that when the central optics dichroic beam splitter is configured to reflect at least part of the device light and at least part of the reflected device light and at least part of the second luminescent material light, it may also be configured to transmit at least part of the first luminescent material light. Likewise, when the central optics dichroic beam splitter is configured to transmit at least part of the device light and at least part of the reflected device light and at least part of the second luminescent material light, it may also be configured to reflect at least part of the first luminescent material light. Hence, the condition of (Ad+10 nm)< Xc2<(Xci-l 0 nm), such that the dichroic beam splitter splits somewhere between and Xci.

The polarizing beam splitter comprised by the central optics may be configured to transmit part of the s-polarized light and reflect part of the s-polarized light. Likewise, it may be configured to reflect at least part of the p-polarized light and transmit at least part of the p-polarized light. The percentage of transmission and reflection for the respective polarization may be defined by the polarizing beam splitter. An example of such partially polarizing beam splitter is e.g. a broadband partially polarizing beam splitter that at 450 nm transmits about 77% of p-polarized light and substantially no s-polarized light, while it may reflect ca. 10% of p-polarized light and 86% of s-polarized light. Especially, the central optics polarizing beam splitter may be configured such that for one polarization the transmittance is not complete, and thus may be partly reflected, whereas for the other polarization, the reflectance may be relatively high, and thus may have a small transmission or essentially no transmission. However, this may also be the other way around.

In specific embodiments, the central optics polarizing beam splitter may be configured to transmit x% of light having p polarization and reflect y% of light having s polarization, wherein one of x% and y% is selected from the range of 15-80%, and the other one of x% and y% is selected from the range of 85-100%. However, other embodiments are herein not excluded.

In specific embodiments, the central optics polarizing beam splitter may be configured to reflect xl% of light having first polarization, reflect yl% of light having a second polarization, and transmit zl % of light having the second polarization. In embodiments, xl may be selected from the range of at least 80% (such as at least 90%, like in embodiments (essentially) 100%), yl is selected from the range of 0-95%, and zl is selected from the range of 5-100%. In specific embodiments, yl is selected from the range of 0-90%, and zl is selected from the range of 10-100%. In more specific embodiments, xl may be selected from the range of at least 80%, yl is selected from the range of 20-90%, and zl is selected from the range of 10-80%. In yet more specific embodiments, xl may be selected from the range of at least 85%, yl is selected from the range of 25-90%, and zl is selected from the range of 10-75%. In yet more specific embodiments, xl may be selected from the range of at least 90%, y 1 is selected from the range of 30-90%, and zl is selected from the range of 10-70% (more especially at least 20%). Hence, 100%-xl of the light having the first polarization may be transmitted. In embodiments, the first polarization is s polarization and the second polarization is p polarization (in aforementioned examples).

Hence, in embodiments the central optics polarizing beam splitter may be configured to transmit a larger part of the p-polarized light than a part of the s-polarized that is reflected. In other embodiments, the central optics polarizing beam splitter may be configured to transmit a larger part of the s-polarized light than a part of the p-polarized that is reflected. In yet other embodiments, the central optics polarizing beam splitter may be configured to reflect a larger part of the s-polarized light than a part of the p-polarized that is transmitted. In yet other embodiments, the central optics polarizing beam splitter may be configured to reflect a larger part of the p-polarized light than a part of the s-polarized that is transmitted. Hence, the central optics polarizing beam splitter may especially be a partially polarizing beam splitter.

Especially, in embodiments (the central optics, more especially) the central optics polarizing beam splitter, may be configured to (a) reflect at least 90% device light when having a first polarization, (b) reflect selected from the range of 20-80% device light when having a second polarization, and (c) transmit selected from the range of 80-20% device light when having the second polarization. As indicated above, in embodiments the first polarization may in embodiments be s or p polarization, and the second polarization may be p or s polarization. However, other embodiments may also be possible.

Especially, in specific embodiments the light generating system may be configured to provide system light comprising one or more of diffused device light, first luminescent material light and second luminescent material light. In embodiments, the system light may comprise essentially no device light that has not been reflected at the reflector. Hence, in specific embodiments the system light may essentially not comprise nondiffused device light.

In embodiments, the device light may have a wavelength selected from the blue wavelength range (see also above), more especially have peak wavelengths selected from the blue wavelength range, and in further specific embodiments the first luminescent material light has a wavelength selected from the green-red wavelength range, the second luminescent material light is selected from the blue-green wavelength range, and in yet further specific embodiments the system light in the first operational mode is white light.

Especially, the control system may be configured to control a spectral power distribution of the system light, y controlling the polarization of the device light, a ratio of one the one hand the (diffused) reflected device light and the second luminescent material light in the system light, and on the other hand the first luminescent material light in the system light may be controlled. Hence, also in this way the spectral power distribution, such as in specific embodiments CCT, may be controlled.

The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.

The control system may also be configured to receive and execute instructions from a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system.

Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Thread, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. The term “operational mode may also be indicated as “controlling mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).

Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme. In specific embodiments, inputs for such a control system may be, next to target setting signals or boundary signals, sensor signals, such as temperature-correlated signals, optical flux correlated signals, and/or optical flux ratio or color point correlated signals, etc.

In specific embodiments, the system light may be white light. Hence, in embodiments, when controlling the polarization control element, the spectral power distribution of the (white) system light may be controlled. In specific embodiments, when controlling one or more of (i) the polarization control element, (ii) a radiant flux of the first device light, and (iii) a radiant flux of the second device light, the spectral power distribution of the (white) system light may be controlled. Therefore, in specific embodiments the correlated color temperature of the system light may be controlled. Yet, in further specific embodiments the control system is configured to control a correlated color temperature of the system light in dependence of one or more of a user interface, a sensor signal, and a timer.

The term “white light”, and similar terms, herein, is known to the person skilled in the art. It may especially relate to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700- 20000 K, for general lighting especially in the range of about 2000-7000 K, such as in the range of 2700 K and 6500 K. In embodiments, e.g. for backlighting purposes, or for other purposes, the correlated color temperature (CCT) may especially be in the range of about 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL.

In specific embodiments, the correlated color temperature (CCT) may be selected from the range of 6000-12000 K, like selected from the range of 7000-12000 K, like at least 8000 K. Yet further, in embodiments the correlated color temperature (CCT) may be selected from the range of 6000-12000 K, like selected from the range of 7000-12000 K, in combination with a CRI of at least 70. In an embodiment, the light source may also provide light source light having a correlated color temperature (CCT) between about 5000 and 20000 K, e.g. direct phosphor converted LEDs (blue light emitting diode with thin layer of phosphor for e.g. obtaining of 10000 K). Hence, in a specific embodiment the light source is configured to provide light source light with a correlated color temperature in the range of 5000-20000 K, even more especially in the range of 6000-20000 K, such as 8000-20000 K. An advantage of the relative high color temperature may be that there may be a relatively high blue component in the light source light.

The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. Herein, UV may especially refer to a wavelength selected from the range of 190-380 nm, such as 200-380 nm.

Here below, some further embodiments are described.

In embodiments, laser banks may be applied. Laser banks may also be used to boast the input power. Therefore, in embodiments the system may comprise a plurality of light generating devices configured in a laser bank. A laser bank may comprise a light emitting arrangement comprising an (2D) array of a plurality of laser diodes arranged on a thermally conductive carrier and a (lens array having a) plurality of collimator lenses corresponding to the laser diodes such that each laser diode of the plurality of laser diodes comprises a collimator lens for collimating laser light emitted by the laser diode. The arrangement may comprise a package architecture or a canned architecture. In case of the package architecture a laser diode chip array is arranged on the thermally conductive carrier. A plurality of electrodes may be present for electrically connecting the plurality of laser diodes.

Further, the system may in embodiments comprise further optics then described above. The term “optics” may especially refer to (one or more) optical elements. Hence, the terms “optics” and “optical elements” and “optical component” may refer to the same items. The optics may include one or more or mirrors, reflectors, collimators, lenses, prisms, diffusers, phase plates, polarizers, diffractive elements, gratings, dichroics, arrays of one or more of the afore-mentioned, etc. Alternatively or additionally, the term “optics” may refer to a holographic element or a mixing rod. In embodiments, the optics may include one or more of beam expander optics and zoom lens optics. See further above for examples of optics. In embodiments, the optics may comprise an integrator, like a “Koehler integrator” (or “Kohler integrator”). In specific embodiments, the system may further comprise one or more of integrating optics, collimation optics, and homogenization optics. One or more of them are also depicted in the accompanying drawings.

The light generating system may be part of or may be applied in e.g. office lighting systems, household application systems, shop lighting systems, home lighting systems, accent lighting systems, spot lighting systems, theater lighting systems, fiber-optics application systems, projection systems, self-lit display systems, pixelated display systems, segmented display systems, warning sign systems, medical lighting application systems, indicator sign systems, decorative lighting systems, portable systems, automotive applications, (outdoor) road lighting systems, urban lighting systems, green house lighting systems, horticulture lighting, digital projection, or LCD backlighting. The light generating system (or luminaire) may be part of or may be applied in e.g. optical communication systems or disinfection systems.

In yet a further aspect, the invention also may provide a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc... The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also may provide a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also may provide a lighting device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system as defined herein. The lighting device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system. For instance, in embodiments the lighting device may comprise a housing or a carrier, configured to house or support one or more of the first light generating device, second light generating device, and one or more of the aforementioned optics. The lighting device may also be an automotive lighting device, such as a headlamp (or headlight) of a motorized vehicle (like a car, a truck, a bus, a coach, a tractor, a boat, an airplane, etc.).

The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to visible light.

The term “centroid wavelength”, also indicated as c, is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula Ac = X A* 1(A) / (S I( A)), where the summation is over the wavelength range of interest, and 1(A) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs. 1-4 schematically depict some embodiments;

Figs. 5a-5b schematically depict some spectral results;

Figs. 6a-6c schematically depict some further embodiments; and Fig. 7 schematically depict some application embodiments. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figs. 1-4 schematically depict some embodiments of the light generating system 1000 (“system” or “system 1000). The light generating system 1000 may comprise (a) one or more light generating devices 100, (b) a first luminescent material arrangement 2100, (c) a reflector-luminescent material arrangement 2500, (d) central optics 900, and (e) a control system 300.

The one or more light generating devices 100 may be configured to generate polarized device light 101 having a controllable polarization and having a device light spectral power distribution; wherein the one or more light generating devices 100 comprise one or more of a laser diode and a superluminescent diode.

The first luminescent material arrangement 2100 may comprise a first luminescent material 210 configured to convert at least part of the device light 101 received by the first luminescent material 210 into first luminescent material light 211 having a first luminescent material light spectral power distribution.

The reflector-luminescent material arrangement 2500 may comprise a reflector 2510 and a second luminescent material arrangement 2200. The reflector 2510 may be configured to reflect at least part of the device light 101 received by the reflector 2510 into reflected device light 711. The second luminescent material arrangement 2200 may comprise a second luminescent material 220 configured to convert at least part of the device light 101 received by the second luminescent material 220 into second luminescent material light 221 having a second luminescent material light spectral power distribution, different from the first luminescent material light spectral power distribution. The central optics 900 may comprise i a central optics polarizing beam splitter 910, and ii a central optics dichroic beam splitter 920; wherein (a) the central optics polarizing beam splitter 910 may be configured to transmit and/or reflect at least part of the device light 101 in dependence of its polarization; and (b) the central optics dichroic beam splitter 920 may be configured to transmit and/or reflect at least part of the device light 101, at least part of the first luminescent material light 211, and at least part of the second luminescent material light 221 in dependence of their [respective] spectral power distributions.

The light generating system 1000 may be configured such that a at least part of the device light 101, when having a first polarization, propagates from the one or more light generating devices 100 via the central optics 900 to the first luminescent material arrangement 2100 to provide the first luminescent material light 211, b at least part of the device light 101, when having a second polarization, different from the first polarization, propagates from the one or more light generating devices 100 via the central optics 900 to the reflector-luminescent material arrangement 2500 to provide the second luminescent material light 221 and the reflected device light 711, and c at least part of the first luminescent material light 211 generated by the first luminescent material arrangement 2100, at least part of the second luminescent material light 221 generated by the second luminescent material arrangement 2200, and at least part of the reflected device light 711 generated at the reflector 2510, escape from the light generating system 1000 via the central optics 900.

The control system 300 may be configured to control the polarization of the device light 101.

The light generating system 1000 may be configured to generate system light 1001 comprising one or more of the first luminescent material light 211, the reflected device light 711, and the second luminescent material light 221 (especially one or more of (i) the first luminescent material light 211 and (ii) the reflected device light 711 and the second luminescent material light 221).

In embodiments, the device light 101 has a device light centroid wavelength Xcd, the first luminescent material light 211 has a first luminescent material light centroid wavelength ci, and the second luminescent material light 221 has a second luminescent material light centroid wavelength L-2, wherein ( d+10 nm)< Xc2<(X<;i-10 nm); wherein device light centroid wavelength L-d is selected from the wavelength range of 400-480 nm, the first luminescent material light centroid wavelength ci is selected from the wavelength range of 490-780 nm, the second luminescent material light centroid wavelength is selected from the wavelength range of 450-520 nm. Especially, in embodiments (X«i+15 nm)< X_C2<(X_CI-50 nm) may apply.

In embodiments, the reflector 2510 may be configured to diffuse at least part of the device light 101 received by the reflector 2510 thereby providing diffused reflected device light 711 while maintaining at least part of the polarization of the device light 101 (wherein the diffuser element 710 is operated in the reflective mode).

In embodiments, the light generating system 1000 further may comprise a polarization changing element 810 configured in an optical path of the device light 101 between the central optics 900 and the reflector 2510. Especially, the polarization changing element 810 may comprise one or more of a X/4 waveplate and a Faraday rotator. Starting with linear s-polarized light, it may be converted by the X/4 element into e.g. right-handed circular pol. Light, which is converted by the polarization maintaining reflective diffuser into left-handed circular polarized light, which now is converted by the X/4 element into linear p- polarized light. Likewise, p-polarized light may be converted into diffused s-polarized light. Hence, device light may pass the polarization changing element twice, one time propagating from the central optics to the reflector (diffuser) element, and having a first polarization, and one time propagating from the reflector (diffuser) element to the central optics, being diffused at the reflector (diffuser) element and obtaining a second polarization when passing the polarization changing element (in the direction of the central optics).

In embodiments, the reflector-luminescent material arrangement 2500 may comprise an (ID or 2D) array of alternating reflectors 2510 and second luminescent material areas 2220 comprising the second luminescent material 220. Other embodiments are also possible (see below).

Characteristic dimensions for ID or 2D array-type configurations, including regular as well as random patterns, may be in the range of 0.01-1 mm, such as 0.05-0.5 mm. Phosphor material may be printed (e.g. via screen printing or jetting) on a reflector, where the reflector may e.g. be a metallized surface textured glass component.

Referring to e.g. Figs. 1 and 4, in embodiments the light generating system 1000 further may comprise a polarization control element 610, wherein the polarization control element 610 may be configured to control polarization of the device light 101 received by the polarization control element 610; and wherein the control system 300 may be configured to control the polarization control element 610. In embodiments, the polarization changing element 610 may comprise a X/2 waveplate.

Referring to Fig. 2, in embodiments the one or more light generating devices comprise two different types of light generating devices 100, differing in the type of polarization of the device light 101 they generate; wherein the light generating system 1000 further may comprise a first polarizing beam splitter 525, wherein the first polarizing beam splitter 525 may be configured downstream of the two different types of light generating devices 100 and upstream of the central optics 900. Further, in embodiments, the first polarizing beam splitter 525 may be configured to transmit (at least part of the) s-polarized light or p-polarized light, and to reflect (at least part of the) p-polarized light or (at least part of the) s-polarized light. Especially, in embodiments the control system 300 may be configured to control the two different types of light generating devices 100.

Referring to Fig. 3, in embodiments the one or more light generating devices comprise two different types of light generating devices 100, differing in a spectral power distribution of the device light 101 they generate; wherein the light generating system 1000 further may comprise a first dichroic beam splitter 515, wherein the first dichroic beam splitter 515 may be configured downstream of the two different types of light generating devices 100 and upstream of the central optics 900; wherein the first dichroic beam splitter 515 may be configured (a) to transmit or reflect at least part of the device light 101 of a first type, and (b) to reflect or transmit at least part of the device light 101 of a second type. Especially, in embodiments the control system 300 may be configured to control the two different types of light generating devices 100.

When using two different blue wavelengths, a polarization rotator (half wavelength plate) may, alternatively, be applied downstream of the first dichroic beam splitter 515 and upstream of the central optics. In the configuration as shown in Fig. 3 the polarization rotator only acts on one of the two types of light generating devices (and not as written controlling both). Further, the combination of dichroic mixing and polarization mixing is possible as well.

Especially, in embodiments the central optics 900 may be configured to (a) reflect at least 90% device light 101 when having a first polarization, (b) reflect selected from the range of 20-80% device light 101 when having a second polarization, and (c) transmit selected from the range of 80-20% device light 101 when having the second polarization.

Further, in embodiments the control system 1000 may be configured to control a spectral power distribution of the system light 1001.

In specific embodiments, the control system 1000 may be configured to control one or more of color rendering index and correlated color temperature of the system light 1001 (by controlling the polarization of the device light 101). Further, in embodiments in a controlling mode of the light generating system 1000 the system light 1001 has one or more of (a) a color rendering index of at least 80, and (b) a correlated color temperature selected from the range of 3000-8500 K.

In specific embodiments (a) the first luminescent material 210 at least may comprise a luminescent material of the type AsBsOn Ce, wherein A may comprise one or more of Y, La, Gd, Tb and Lu, and wherein B may comprise one or more of Al, Ga, In and Sc, and/or (b) the second luminescent material 220 at least may comprise one or more of Nao.sKo.sLisSiC^Eu² , MSi2O2N2: Eu²⁺, wherein M may comprise one or more of Ba, Sr, and Ca, Sr[BeeON4]:Eu²⁺, and MAhC^Eu² , wherein M may comprise one or more of Ba, Sr, and Ca.

In embodiments, the luminescent material 200 may be configured in thermal contact with a thermally conductive material. This may apply to the first luminescent material 210 and/or the second luminescent material 220. Further, in embodiments the light generating system 1000 may comprise a plurality of light generating devices 100 configured to generate the device light 101, wherein two or more of the light generating devices 100 comprise laser light sources configured in a laser bank.

Referring to Figs. 1-4, the light generating system 1000 may comprise a rotatable element 1200, wherein the rotatable element 1200 may comprise the first luminescent material 210; wherein in an operational mode of the light generating system 1000 the rotatable element 1200 rotates, such that over time different parts of the first luminescent material 210 are irradiated by the device light 101. The rotatable element 1200 may rotate about the axis AR. However, alternatively or additionally, the light generating system 1000 may comprise a (further) rotatable element, wherein the (further) rotatable element may comprise the second luminescent material 220; wherein in an operational mode of the light generating system 1000 the (further) rotatable element rotates, such that over time different parts of the second luminescent material 220 are irradiated by the device light 101. For controlling the (further) rotatable element 1200, an actuator (not depicted) may be applied.

In embodiments, the system may function with a static luminescent converter, but in embodiments a phosphor wheel may be used here due to its good heat spreading and cooling properties. The diffuser may typically dissipate less energy and may not be in a need of such a rotatable configuration, although a rotatable configuration of the diffuser is also an embodiment herein. Hence, in embodiments the diffuser may also be realized in the form of a rotating wheel. For static luminescent converters in particular, liquid cooled converter configurations may also enable high optical power as well as high optical power density. Overall, a typical advantage may be that in embodiments from two (different) laser sources only part of one source may be used for diffusion and more than one source for luminescent conversion. Thereby, such embodiments may enable the most efficient use of a combination of two laser sources while also enabling maximum output light using two laser sources, e.g. when using two sources with comparable dimensions (e.g. the same number of laser diodes in convenient configurations). Hence, there may be one or more rotatable elements, with the second luminescent material comprised by a rotatable element and/or the first luminescent material and the reflector comprised by the rotatable element.

In embodiments, the luminescent material 200 may be configured in thermal contact with a thermally conductive element. For instance, the luminescent material 200 may be configured in thermal contact with a thermally conductive material. This may apply to the first luminescent material 210 and/or the second luminescent material 220.

Further, in specific embodiments the light generating system 1000 may in addition comprise one or more of integrating optics, collimation optics, and homogenization optics. For instance, reference 560 refers to lenses, especially used for collimation of light. Reference 550 refers to integrators, which may especially be used to beam shape and homogenize light. However, further optics than schematically depicted may be available.

Laser diode (LD) banks are typically being offered with a center wavelength (WL) of 455 nm or 465 nm. Although the longer wavelength blue LD’s show a somewhat lower external quantum efficiency (EQE), or wall plug efficiency (WPE), and optical output power (P_Opt), the luminous equivalence (LE) is significantly higher thanks to the larger overlap with the eye sensitivity curve. While for a 455 nm line emitter the LE is just below 33 lm/Wopt, at 465 nm this is 50 lm/W_opt, so this outperforms the difference in EQE. Furthermore, with a longer wavelength blue primary in the overall spectrum the cyan gap as typically present in a laser-phosphor (or LED-phosphor) output spectrum is reduced and with that the CRI is increased. Therefore it is advantageous to use the longer wavelength blue where possible as the blue contribution in the white output light of a light engine. Thanks to the very small etendue of the LDs the laser beams can be collimated very well, and thanks to the narrow spectral width of LDs of only a few nm, dichroic beam splitting and combining is possible for such beams with quite small difference in wavelength of these beams. This may enable configurations in which the longer WL is substantially used as a contribution in the white output light as well as (partly) used for pumping one or more luminescent material 200s. Thanks to the typically quite broad absorption spectra of e.g. garnet or nitride phosphors, these materials can be excited with both the longer and the shorter blue WL laser beams.

Thanks to the application of a birefringent rotator, the color temperature of the output light can be adjusted without substantially changing the light engine output power while keeping the input power constant. Thanks to the use of a partially polarizing beam splitter, the light engine shows high efficiency. Thanks to the configuration that is based purely on diffuse reflected laser light, a light engine with high robustness concerning eye safety may be realized. The use of a dichroic beam splitter in combination with the combined polarizing beam splitter - dichroic beam splitter (PBS-DBS) may enable further increased light engine output flux and radiance.

Hence, amongst others herein in embodiments a color tunable high brightness and high flux light source based on laser phosphor conversion at two different spots and splitting of a blue laser beam by a partially polarizing beam splitter is proposed. Thanks to the use of shifted color primaries towards cyan for the short wavelength primary and towards orange for the long wavelength primary) the color points achieved by the combination are for a larger CCT range close to the BBL, while also the color quality is improved. The blue source may comprise laser diode (LD) or super luminescent diode (SLD) emitters. The system may further be based on diffuse (partial) reflection of blue light, dichroic mixing of at least two spectrally different light beams, an adjustable ratio of two polarization directions of the LD- or SLD-generated light, and an especially (at least partly) polarization maintaining diffuser. With light engine configurations proposed herein, highly efficient collection of the various spectral contributions to the output light may be realized in a compact configuration while the color point of the (white) output light is easily tunable over a relatively large color temperature range of interest with reduced deviation from the BBL and with improved color quality.

Amongst others, herein a light engine architecture is described for providing high flux high brightness speckle-free (white) light that may enable easy factory-calibration with respect to the requested color point and/or easy color point adjustment by the user, where the color point deviation from the BBL may be limited thanks to the chosen color primaries. Color tunability is provided along a line in the chromaticity diagram that is substantially parallel to the black body locus (BBL) in at least the color temperature range of primary interest. The proposed configuration may provide highly efficient collection of all the spectral contributions to the output light, resulting in a high efficiency high brightness light engine. In addition, configurations are provided by which the output flux of the system can be further increased.

In Fig. 1, a basic configuration for a laser-phosphor light engine with tunable color point is schematically depicted, as well as multiple variants covered by the main principles, all of which comprise a partially polarizing beam splitter and projection of blue light to at least two spots where the blue light is, respectively, fully and partially converted into luminescent light, of which some are further depicted in other schematical drawings. From the spot where the light is partially converted, also diffuse reflected blue light may be collected to provide the blue spectral contribution to the (white) output light. Although we describe the sources as laser sources or laser diodes, also superluminescent or other light emitting diodes may be applied. Although there are many different types of laser diodes, such as edge emitting laser diodes, vertical cavity surface emitting laser diodes, and many others, they all may be applied, either as individual emitter or as array of emitters. The only boundary condition is that there is some degree of polarization as that is the basis for the creation of color point tunability.

Fig. 1 schematically depicts a configuration of the proposed light engine: using a waveplate to tune the engine output color by adjusting, via rotation of the birefringent rotator waveplate, the ratio of s- and p-polarized light originating from a laser diode (array) entering the PBS/DBS, a partially polarizing beam splitter to split the blue laser light, a phosphor wheel for full conversion to a longest wavelength luminescent light and a combined luminescent converter / diffuse reflector that converts partly into shortest wavelength luminescent light. The longest luminescent wavelength light, shortest wavelength luminescent light, and the diffused blue light may be combined by the combined partially polarizing (for blue) and dichroic (for yellow-red vs cyan-green and p-polarized blue) beam splitter. The PBS may reflect >90% of s-polarized blue light and 50-80% of p-polarized blue light, while transmitting 10-40% of the p-polarized blue light. The DBS function may provide >90% transmittance of the longest wavelength (yellow-red) luminescent light, and >90% reflectance of the shortest wavelength (cyan-green) luminescent light.

In this configuration the diffuser function for blue light may be combined with a partial conversion of blue light into short wavelength luminescent light, typically in the cyan-green spectral range. By this partial conversion a color point is achieved that, in combination with the color point of the long wavelength luminescent light, typically in the yellow-red spectral range, in a chromaticity diagram may provide a connecting line between these two color points that is substantially parallel to the BBL in the color temperature range of interest for the (white) engine output light. Therefore, the transmission of p-polarized light by the PBS is in this case higher than in a configuration without partial luminescent conversion. The PBS may have a reflectance >90% for s-polarized blue light, 50-80% reflectance for p-polarized blue light, and 20-50% transmittance for p-polarized blue light. The dichroic beam splitting function may provide >90% transmittance for the longest wavelength (yellow-red) luminescent light and >90% reflectance for the shortest wavelength (cyan-green) luminescent light.

Here below, some working principles of this basic configuration are described:

1. In this configuration longer wavelength (yellow-red) luminescent light may be combined with blue light and shorter wavelength (cyan-green) luminescent light to create color tunable white light by adjusting the ratio between these two, resulting in an adjustable color point that substantially follows the direction of the BBL in the color temperature range of primary interest.

2. A single at least partially polarized light source comprising one or more electro-optical components is used in combination with a birefringent rotator, a beam splitter that almost fully may reflect one polarization and splits the other polarization in two sizeable potions, a phosphor wheel (or other rotatable element), and a diffuser may be combined to create a high-flux source with tunable color point.

3. With setting the optical axis of a birefringent rotator relative to the (main) polarization axis of the blue light the ratio of blue in the different branches is set, enabling fine-tuning of the resulting (white) output color point.

4. The blue PBS and cyan-green / yellow-red DBS component does not fully split the two polarizations of the incoming blue beam as is the case with common polarizing beam splitters, but may reflect one of them (almost) completely (or at least substantially (>60%)) and may reflect the other of them substantially (>60%), so as to transmit a smaller fraction (<40%) of the incoming blue beam.

5. The reflected blue light is projected onto the longer wavelength (yellow-red) emitting luminescent material ring on the spinning wheel; this ring may comprise a single luminescent material, a mixture of luminescent materials, and/or multiple ring segments with different luminescent characteristics.

6. The longer wavelength luminescent light may be collected and transmitted through the (blue PBS and) cyan-green reflective and yellow-red transmissive DBS to the output.

7. The transmitted blue (p-pol.) light is passing a X/4 plate and projected onto a shorter wavelength (cyan-green) emitting luminescent material and preferably at least partially polarization maintaining reflective diffuser.

8. The diffused blue light and the shorter wavelength luminescent light are collected and pass again the X 4 plate (in which case the blue light becomes substantially s- pol. light), and at the DBS the blue light is predominantly reflected (i.e., the diffused s-pol. light is (almost) completely or at least substantially reflected, and the diffused p-pol. light is substantially reflected), while the shorter wavelength luminescent light is (almost) completely reflected, upon which this diffused blue light and the shorter wavelength luminescent light may be combined with the longer wavelength luminescent light into (white) output light.

9. An optional integrator is used to further homogenize the white light beam.

The basic configuration was described in the previous section. In this configuration a static diffuser/converter combination was applied, as for this component the thermal dissipation may be limited, while for the full conversion branch a rotating phosphor wheel was applied to enable maximum irradiance (and resulting radiance) of the luminescent material. A partially polarizing beam splitter is used in the form of a combined PBS&DBS; this component combines the partially polarizing beam splitting/combining functionality for blue light with the dichroic beam splitting/combining of s-polarized blue and the longer wavelength luminescent light. To minimize blue power losses further, a better polarization maintaining diffuser may be used in combination with the addition of a X/4 plate. In case of full polarization conservation, this would even result in 0% losses of the diffused blue light.

Cyan emitting phosphors that can be excited with blue light with a small Stokes shift have been and are being investigated e.g. to enable realization of a full spectrum or improved color quality white light emitting LED. Various luminescent materials may be applicable. For example, Nao.sKo.sLisSiOtEu² (NKLSO:Eu²⁺) phosphor was developed with impressive properties, providing blue-excited cyan emission at 486 nm with a narrow full width at half maximum (FWHM) of only 20.7 nm, and good thermal stability with an integrated emission loss of only 7% at 150 °C [Zhao, M., Liao, EL, Molokeev, M.S. et al. Emerging ultra-narrow-band cyan-emitting phosphor for white LEDs with enhanced color rendition. Light Sci Appl 8, 38 (2019). https://doi.org/10.1038/s41377-019-0148-8]. The PL (photoluminescent) spectrum of the NKLSO:8%Eu2+ phosphor consists of a dominant asymmetric narrow-band peak at 486 nm (FWHM = 20 nm).

Although the NKLSO:Eu phosphor may still be suffering from stability issues, this is something that may be expected to improve with further surface engineering of the phosphor. From the spectral point of view we see that, when using a dichroic filter with a cutoff somewhat above 500 nm, spectral filtering losses are quite limited, while also thermal quenching is quite modest. The latter should not be significant in most high brightness and high flux applications, as generally only a relatively small amount of cyan is required to shift the blue color point to longer wavelengths and no other luminescent conversion takes place in the blue-cyan color channel.

An embodiment of a cyan phosphor is also BaSi2ON2: Eu²⁺, which possesses an emission band with the peak at -495 nm (FWHM = -32 nm). In addition, there are cyan emitting aluminate phosphors, as well as a narrow-band cyan-emitting oxonitridoberyllate phosphor Sr[BeeON4]:Eu²⁺ (L-m = 495 nm, FWHM = 35 nm).

Spectral modeling was performed for a relatively broad band, short wavelength garnet emission, pumped by a 445 nm laser beam, to provide, in combination with a dichroic filter with cut-off wavelength of either 510 nm or 520 nm, the cyan spectrum. This results in the first color primary of the light engine, comprising blue light in combination with cyan light. A longer wavelength garnet phosphor (Gd-YAG:Ce), pumped by blue laser light may provide the second, yellow-orange color primary, that may be combined via the dichroic filter with the blue-cyan contribution into white output light. In this modelling, the ratio of yellow-orange to blue-cyan was varied, resulting in color points along a line connecting both color primaries. The resulting spectra are plotted in Fig. 5a. In this figure “white” light output spectra for varying contributions (ranging from 0 to 100% of the output light) of yellow-orange and blue-cyan light, using a dichroic cut-off wavelength of 510 nm and a blue pump wavelength of 445 nm are depicted. Note that the first luminescent material 210 and the second luminescent material may thus have an excitation band (especially in the blue wavelength range), at least partly overlapping with a device light (emission band) 101. Referring to Fig. 5a, in embodiments about Xc2<(Xci-50 nm). Further, (Xcd+20 nm)< L-2, may apply. Especially, (a) the centroid wavelength and/or peak wavelength of the device light, and the centroid wavelength of the second luminescent material light and (b) the centroid wavelength of the first luminescent material may be selected such that the peak wavelength and/or centroid wavelength of the device light and the centroid wavelength of the second luminescent material light on the one hand and the centroid wavelength of the first luminescent material light on the other hand are spectrally positioned at two opposite sides of a cut-on / cut-off wavelength of a dichroic filter comprised by the central optics. For instance, such cut-on / cut-off wavelength may ideally be chosen at the dashed line at about 505 nm in Fig. 5a, for the chosen luminescent materials (and light generating device).

The relative spectral power contributions of blue, cyan, and yellow-orange as a function of the correlated color temperature are plotted in Fig. 5b. In this figure spectral power contributions of blue, cyan, and yellow-orange light in the white output light for color temperatures between 3000K and 8000K and a dichroic filter cut-off wavelength of 510 nm are plotted. A short- wavelength garnet was used for the cyan spectral contribution, while a long-wavelength garnet was used for the yellow-orange color primary, such that the bluecyan and yellow-orange color primaries are connected via a line along the BBL.

The color primaries in combination with the dichroic filter high/low pass wavelength have been chosen such that the color points in a large range of color temperatures are close to, and often even within 5 SDCM from, the BBL.

The results were compared to conventional system. While the conventional system with a blue and a garnet color point shows a very small color temperature range where the color point is near the BBL, for the systems with a blue-cyan first primary the color points are close to the BBL in a much larger color temperature range, enabling more useful color point tunability. Apart from the color point tunability along the BBL, another advantage of adding cyan to the first color primary is that the white light quality can be improved. In particular for the lower color temperatures this matters most. While for the combination of blue light with garnet luminescent emission the CRI is generally around 70, with the dichroic addition of cyan the CRI can be increased to just above 80 in the color temperature range of ca 4500 - 6000 K.

In alternative embodiments, the full conversion luminescent material is not applied on a rotating wheel but directly on a heat sink. This limits the maximum flux and radiance of the light engine output light, but results in a mechanically simple configuration without any gyroscopic effects, which may be favorable in several applications where the beam orientation is varied.

In further alternative embodiments, not only the full conversion luminescent material may be applied on a rotating wheel, but also the partially converting luminescent and partly diffuse reflecting material may be applied on a rotating wheel, either mixed or applied in various segments.

In yet further alternative embodiments, the luminescent material track on a rotating wheel may comprise one or multiple luminescent materials and may be applied as a single (uniform) ring (segment) or as multiple ring segments that may have different luminescent properties.

However, there is a need for higher brightness and higher flux light engines. For that, the blue input light may comprise both s- and p-polarized light, e.g. by combining two laser sources via a PBS. However, in that case the requirements for the PBS&DBS component change. Optical simulations have shown that, when using input blue light comprising both p- and s-polarized light, a preferred p-polarized transmittance of 41% results. This is, however, also a function of the desired color temperature around which one would want to vary the color temperature. Nevertheless, it shows that this is fundamentally different from using only a p-polarized input as Maxell does do. Based on this insight, a further embodiment according to the invention, described in more detail as variant of the basic configuration (as schematically depicted in Fig. 1), is presented in Fig. 2.

Fig. 2 schematically depicts an embodiment using two laser light sources (laser diode arrays) with opposite (complementary) polarization that may be combined via a first PBS that (almost) fully may reflect one polarization and (almost) fully transmits the other polarization. By adjusting, via the drive currents of the two laser sources, the ratio of s- and p-polarized light in the combined blue light beam that enters the subsequent PBS/DBS being a partially polarizing beam splitter for blue light the ratio of optical powers from the two branches of the engine may be adjusted, and with that the color point of the output light. A static luminescent converter on a heat sink may provide full conversion to a longest wavelength luminescent light. A combined luminescent converter / diffuse reflector that converts part of the incident blue light may provide a combination of shortest wavelength luminescent light and diffused blue light. The longest wavelength luminescent light, the shortest wavelength luminescent light, and the diffused blue light may be combined by the combined partially polarizing (for blue) and dichroic (for yellow-red vs cyan-green and p- polarized blue) beam splitter. The PBS may reflect >90% of s-polarized blue light and 30- 60% of p-polarized blue light, while transmitting 40-70% of the p-polarized blue light. The DBS function may provide >90% transmittance of the longest wavelength (yellow-red) luminescent light, and >90% reflectance of the shortest wavelength (cyan-green) luminescent light.

Here below, some working principles of this configuration are described:

1. For the generation of the blue input light of the engine, two addressable and at least partially polarized light sources are used, each comprising one or more electro-optical components. The two laser beams may be combined via a polarizing beam splitter that almost completely transmits one specific polarization (p-pol) of the blue light source light and may reflect the other (opposite) polarization (s-pol) of the blue light source light.

2. Further splitting and combining of the pump and converted light beams are identical as in the basic configuration described above.

3. In this embodiment the spinning phosphor wheel is replaced by a static luminescent converter on a heat sink, creating a light engine with reduced maximum radiance but with a very simple yet color-tunable configuration.

A further embodiment according to the invention, is presented in Fig. 3. In this configuration, next to the extended tunability by the additional polarization rotator as presented in the previous variant, two different wavelengths of the blue laser sources are used to enable optimal pumping of the (cyan) luminescent conversion material in the branch that also may provide the main blue contribution to the output white light.

In Fig. 3, the longest wavelength blue laser source is configured to provide s- pol. light to the PBS 515 and the central PBS&DBS components (i.e. central optics 900). The shortest wavelengths blue laser source should be at least partly polarized, and its s/p polarization ratio is set via a birefringent rotator. The shortest wavelength blue is provided here as pump wavelength for the shortest wavelength emitting luminescent material. PBS 515 = Polarizing Beam Splitter (blue); >90% s-pol. refl., >90% p-pol. transm. PBS = Polarizing Beam Splitter (blue); >90% s-pol. reflectance, 50-80% p-pol. reflectance, 20-50% p-pol. transmittance DBS = Dichroic Beam Splitter (cyan-green / yellow-red); >90% yellow-red transmittance, >90% cyan reflectance.

Here below, some working principles of this configuration are described: 1. In this variant, two different blue wavelengths are used, tuned to optimally pump the different luminescent materials in the two optical branches. 2. Color point tuning is possible by both adjusting the relative optical powers of the two laser sources with different polarization and by adjusting the orientation of the optical axis of the birefringent rotator.

3. As the luminescent converter that may be applied on the ring that also comprises the diffuse reflector emits the shortest wavelength luminescent light, in this optical branch preferably a shorter wavelength blue is used to pump the luminescent material; therefor the laser source with the longest wavelength, that is more suitable for pumping luminescent material emitting at longer wavelengths, is configured preferably as the s- polarized blue source.

Referring to Figs. 2 and 3, embodiments are schematically depicted wherein there are a plurality of light generating devices 100, comprises at least a first light generating device and a second light generating device, which may differ in one or more of the polarization of the device light 101 they generate and/or the spectral power distribution of the device light 101 they generate. By controlling the radiant fluxes of the different types of (light sources or) light generating devices, the polarization of the (resulting) device light, i.e. the device light 101 downstream from the polarizing beam splitter 525 (Fig. 2) of dichroic beam splitter 515 (Fig. 3), may be controlled, and thereby the spectral power distribution of the system light 1001. The different types of light generating devices 100 are above also indicated with first light generating devices (configured to generate first device light) and second light generating device (configured to generate second device light).

In further variants, the (split) blue light beams are projected on two different spots on one and the same rotating object such as a rotating wheel, cylinder, or rod. Therefore, in a further embodiment, and serving as an example for any embodiment with a rotating wheel, cylinder, or rod that comprises both or more tracks, the track providing partly luminescent light and partly diffused blue light may be realized in the form of a ring on a spinning wheel that is concentric with a full conversion ring-shaped luminescent material track. A specific configuration, where both tracks have been partitioned in segments with different optical properties, is illustrated in Figs. 4 and 6b. In this configuration the inner ring-shaped track comprises blue light diffusing and blue light pumped luminescent segments, and the outer ring-shaped track comprises luminescent segments with different luminescent properties.

Here below, some working principles of this configuration are described: 1. The working principles of beam splitting and combining are the same as in the basic configuration, as schematically depicted in Fig. 1, but the different blue spots are projected onto different tracks that are located on one and the same rotating wheel.

2. The ring comprising the reflective diffuser in this embodiment also comprises a luminescent material, e.g. in one or more segments of the ring.

3. The luminescent part(s) of the ring may be partly luminescent converting, in which case also (a substantial) part of the incident blue light is (substantially) diffuse reflected, or may be (almost) fully converting the incident blue light into luminescent light; in case the luminescent material is present along the full ring it has to be partially converting to provide also the required diffusively reflected blue light.

4. The Luminescent converter comprised on the ring that also may provide the diffused blue light has a spectral emission with a center wavelength that is preferably shorter than the center wavelength of the luminescent emission from the ring emitting only luminescent light.

5. The PBS/DBS component in this case needs to transmit quasi the full spectrum from the fully luminescent ring, while reflecting quasi the full spectrum of the luminescent emission from the ring that also may provide the diffusively reflected blue light to the white output light of the engine.

6. Different segments of the ring that also may provide the diffused blue light may provide different luminescent emission or different diffusively reflected blue light.

7. Various segments may comprise identical luminescent material, by which the repetition rate for emission of light with that particular spectrum in the output light is increased and therefore possible temporal artifacts can (almost arbitrarily much) be reduced.

8. The ring that contributes to the output light only with luminescent light also may comprise one or more luminescent materials in one or more segments.

9. With the luminescent material on the ring that may provide also diffused blue light emitting at a wavelength (typically in the cyan-green spectral range) that is shorter than the luminescent material at the fully luminescent ring (typically in the green/yellow-red spectral range) and provided in the right amount, the color point of the output light can be varied along a line that is substantially parallel to the BBL in a color temperature range of primary interest (e.g. 4000 - 7000 K).

10. To minimize visibility or detectability of temporal artifacts, in particular chromatic temporal contrasts, the layout of the rings is preferably such that the color point variation in time is minimized, e.g. by always combining yellow with blue light or cyan with red light rather than at some moment combining blue with cyan light and at another moment yellow with red light.

It may be obvious that multiple other permutations of building blocks / subsystems as presented so far are covered as further embodiments according to the principles of this invention as well.

In yet further embodiments according to this invention, as variants of any of the preceding embodiments, the laser source, or, in case of presence of two different laser source at least one of these source, may be high frequency and/or amplitude modulated to enable optical wireless communication (OWC).

As luminescent materials are generally far slower in their temporal response (i.e., in their decay rate) compared to the lasers, preferably the blue laser light is used for this OWC. In particular in those configurations where one laser source is used to provide s- polarized light and a second laser source is used to provide p-polarized blue light, it is advantageous to only modulate the source providing the p-polarized light because the s- polarized light is (almost) fully used for luminescent conversion.

Finally, further variations are possible by using transmissive phosphor (wheel) elements and/or transmissive diffusive elements or transmissive combined partially luminescent converting and blue light diffusing elements. Such variations are based on the same principles as described above and are considered as covered by this invention as well.

Fig. 6a schematically depict embodiments of rotatable elements with different configuration of luminescent materials, e.g. with one or two luminescent materials, though more than two may be possible. Radial configurations may (thus) also be possible.

As indicated above, in Fig. 6b an embodiment of a rotating wheel that comprises both or more tracks, the track providing partly luminescent light and partly diffused blue light is realized in the form of a ring on a spinning wheel that is concentric with a full conversion ring-shaped luminescent material track. A specific configuration, where both tracks have been partitioned in segments with different optical properties, is illustrated in Fig 6b. In this configuration the inner ring-shaped track may comprise blue light diffusing and blue light pumped luminescent segments, and the outer ring-shaped track comprises luminescent segments with different luminescent properties. Other configurations may also be possible.

Referring to Fig. 6c, in embodiments, the second luminescent material 220 may be configured on at least part of the reflector 2510, wherein one or more of the following applies: (i) the luminescent material 220 only partly covers the reflector 2510, and (ii) the luminescent material 220 is (also) configured to transmit part of the device light 101 received by the luminescent material 220. The luminescent material may be transparent (as e.g. the case for quantum dot materials in a transparent matrix, nano-sized inorganic luminescent particles in a transparent matrix, polycrystalline inorganic luminescent material sintered and pressed to transparency, or monocrystalline luminescent material) or scattering (as e.g. the case for large inorganic phosphor particles in a matrix material) for the incident device light.

Alternatively and/or additionally, there may be a stacked layer configuration in which e.g. the top layer comprises a transparent luminescent material which may or may not be patterned and the bottom comprises the diffuse reflector (mounted on or being integral part of a heat sink).

Fig. 7 schematically depicts an embodiment of a luminaire 2 comprising the light generating system 1000 as described above. Reference 301 indicates a user interface which may be functionally coupled with the control system 300 comprised by or functionally coupled to the light generating system 1000. Fig. 7 also schematically depicts an embodiment of lamp 1 comprising the light generating system 1000. Reference 3 indicates a projector device or projector system, which may be used to project images, such as at a wall, which may also comprise the light generating system 1000. Hence, Fig. 7 schematically depicts embodiments of a lighting device 1200 selected from the group of a lamp 1, a luminaire 2, a projector device 3, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system 1000 as described herein. In embodiments, such lighting device may be a lamp 1, a luminaire 2, a projector device 3, a disinfection device, or an optical wireless communication device. Lighting device light escaping from the lighting device 1200 is indicated with reference 1201. Lighting device light 1201 may essentially consist of system light 1001, and may in specific embodiments thus be system light 1001. Reference 1300 refers to a space, such as a room. Reference 1305 refers to a floor and reference 1310 to a ceiling; reference 1307 refers to a wall.

The term “plurality” refers to two or more.

The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” also includes embodiments wherein the term

“comprises” means “consists of’.

The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) may provide a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method as described herein.

The invention also may provide a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also may provide a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS:

1. A light generating system (1000) comprising (i) one or more light generating devices (100), (ii) a first luminescent material arrangement (2100), (iii) a reflector- luminescent material arrangement (2500), (iv) central optics (900), and (v) a control system (300), wherein: the one or more light generating devices (100) are configured to generate polarized device light (101) having a controllable polarization and having a device light spectral power distribution; wherein the one or more light generating devices (100) comprise one or more of a laser diode and a superluminescent diode; the first luminescent material arrangement (2100) comprises a first luminescent material (210) configured to convert at least part of the device light (101) received by the first luminescent material (210) into first luminescent material light (211) having a first luminescent material light spectral power distribution; the reflector-luminescent material arrangement (2500) comprises a reflector (2510) and a second luminescent material arrangement (2200); the reflector (2510) is configured to reflect at least part of the device light (101) received by the reflector (2510) into reflected device light (711); the second luminescent material arrangement (2200) comprises a second luminescent material (220) configured to convert at least part of the device light (101) received by the second luminescent material (220) into second luminescent material light (221) having a second luminescent material light spectral power distribution, different from the first luminescent material light spectral power distribution; the central optics (900) comprises (i) a central optics polarizing beam splitter (910), and (ii) a central optics dichroic beam splitter (920); wherein: the central optics polarizing beam splitter (910) is configured to transmit and/or reflect at least part of the device light (101) in dependence of its polarization; the central optics dichroic beam splitter (920) is configured to transmit and/or reflect at least part of the device light (101), at least part of the first luminescent material light (211), and at least part of the second luminescent material light (221) in dependence of their spectral power distributions; the light generating system (1000) is configured such that (a) at least part of the device light (101), when having a first polarization, propagates from the one or more light generating devices (100) via the central optics (900) to the first luminescent material arrangement (2100) to provide the first luminescent material light (211), (b) at least part of the device light (101), when having a second polarization, different from the first polarization, propagates from the one or more light generating devices (100) via the central optics (900) to the reflector-luminescent material arrangement (2500) to provide the second luminescent material light (221) and the reflected device light (711), and (c) at least part of the first luminescent material light (211) generated by the first luminescent material arrangement (2100), at least part of the second luminescent material light (221) generated by the second luminescent material arrangement (2200), and at least part of the reflected device light (711) generated at the reflector (2510), escape from the light generating system (1000) via the central optics (900); the control system (300) is configured to control the polarization of the device light (101); the light generating system (1000) is configured to generate system light (1001) comprising one or more of the first luminescent material light (211), the reflected device light (711), and the second luminescent material light (221); and wherein the light generating system (1000) further comprises a polarization control element (610), wherein the polarization control element (610) is configured to control polarization of the device light (101) received by the polarization control element (610); and wherein the control system (300) is configured to control the polarization control element (610); wherein the polarization control element (610) is configured between at least one of the light generating devices (100) and the central optics (900).

2. The light generating system (1000) according to claim 1, wherein the device light (101) has a device light centroid wavelength Xcd, the first luminescent material light (211) has a first luminescent material light centroid wavelength Xci, and the second luminescent material light (221) has a second luminescent material light centroid wavelength Xc2, wherein (Xcd+10 nm)< Xc2<(X<;i-10 nm); wherein device light centroid wavelength Xcd is selected from the wavelength range of 400-480 nm, the first luminescent material light centroid wavelength Xci is selected from the wavelength range of 490-780 nm, the second luminescent material light centroid wavelength is selected from the wavelength range of 450-520 nm; and wherein the reflector (2510) is configured to diffuse at least part of the device light (101) received by the reflector (2510) thereby providing diffused reflected device light (711) while maintaining at least part of the polarization of the device light (101).

3. The light generating system (1000) according to any one of the preceding claims, wherein the light generating system (1000) further comprises a polarization changing element (810) configured in an optical path of the device light (101) between the central optics (900) and the reflector (2510); wherein the polarization changing element (810) comprises one or more of a X/4 waveplate and a Faraday rotator.

4. The light generating system (1000) according to any one of the preceding claims 1-3, wherein the reflector-luminescent material arrangement (2500) comprises an array of alternating reflectors (2510) and second luminescent material areas (2220) comprising the second luminescent material (220).

5. The light generating system (1000) according to any one of the preceding claims 1-3, wherein the second luminescent material (220) is configured on at least part of the reflector (2510), wherein one or more of the following applies: (i) the luminescent material (220) only partly covers the reflector (2510), and (ii) the luminescent material (220) is configured to transmit part of the device light (101) received by the luminescent material (220).

6. The light generating system (1000) according to any one of the preceding claims, wherein the polarization control element (610) comprises a rotatable birefringent rotator.

7. The light generating system (1000) according to any one of the preceding claims, wherein the one or more light generating devices comprise two different types of light generating devices (100), differing in the type of polarization of the device light (101) they generate; wherein the light generating system (1000) further comprises a first polarizing beam splitter (525), wherein the first polarizing beam splitter (525) is configured downstream of the two different types of light generating devices (100) and upstream of the central optics (900); and wherein the first polarizing beam splitter (525) is configured to transmit s- polarized light or p-polarized light, and to reflect p-polarized light or s-polarized light; and wherein the control system (300) is configured to control the two different types of light generating devices (100).

8. The light generating system (1000) according to any one of the preceding claims, wherein the one or more light generating devices comprise two different types of light generating devices (100), differing in a spectral power distribution of the device light (101) they generate; wherein the light generating system (1000) further comprises a first dichroic beam splitter (515), wherein the first dichroic beam splitter (515) is configured downstream of the two different types of light generating devices (100) and upstream of the central optics (900); wherein the first dichroic beam splitter (515) is configured (a) to transmit or reflect at least part of the device light (101) of a first type, and (b) to reflect or transmit at least part of the device light (101) of a second type; wherein the control system (300) is configured to control the two different types of light generating devices (100).

9. The light generating system (1000) according to any one of the preceding claims, wherein the central optics polarizing beam splitter (910) is configured to (a) reflect at least 90% device light (101) when having a first polarization, (b) reflect selected from the range of 20-80% device light (101) when having a second polarization, and (c) transmit selected from the range of 80-20% device light (101) when having the second polarization.

10. The light generating system (1000) according to any one of the preceding claims, wherein the control system (1000) is configured to control one or more of color rendering index and correlated color temperature of the system light (1001); wherein in a controlling mode of the light generating system (1000) the system light (1001) has one or more of (a) a color rendering index of at least 80, and a correlated color temperature selected from the range of 3000-8500 K.

11. The light generating system (1000) according to any one of the preceding claims, wherein the first luminescent material (210) at least comprises a luminescent material of the type AsBsO Ce, wherein A comprises one or more of Y, La, Gd, Tb and Lu, and wherein B comprises one or more of Al, Ga, In and Sc.

12. The light generating system (1000) according to any one of the preceding claims, wherein the second luminescent material (220) at least comprises one or more of Nao.sKo.sLisSiCE Eu² , MSi2C>2N2: Eu²⁺, wherein M comprises one or more of Ba, Sr, and Ca, Sr[BeeON4]:Eu²⁺, and MAhC^Eu² , wherein M comprises one or more of Ba, Sr, and Ca.

13. The light generating system (1000) according to any one of the preceding claims, wherein the luminescent material (200) is configured in thermal contact with a thermally conductive material; wherein the light generating system (1000) comprises a plurality of light generating devices (100) configured to generate the device light (101), wherein two or more of the light generating devices (100) comprise laser light sources configured in a laser bank.

14. The light generating system (1000) according to any one of the preceding claims, comprising a rotatable element (1200), wherein the rotatable element (1200) comprises the first luminescent material (210); wherein in an operational mode of the light generating system (1000) the rotatable element (1200) rotates, such that over time different parts of the first luminescent material (210) are irradiated by the device light (101).

15. A lighting device (1200) selected from the group of a lamp (1), a luminaire (2), a projector device (3), a disinfection device, a photochemical reactor, an automotive lighting device, and an optical wireless communication device, comprising the light generating system (1000) according to any one of the preceding claims.