WO2021007148A1 - Système de conversion de phosphore sélectif en longueur d'onde pour dispositifs d'éclairage laser - Google Patents

Système de conversion de phosphore sélectif en longueur d'onde pour dispositifs d'éclairage laser Download PDF

Info

Publication number
WO2021007148A1
WO2021007148A1 PCT/US2020/040868 US2020040868W WO2021007148A1 WO 2021007148 A1 WO2021007148 A1 WO 2021007148A1 US 2020040868 W US2020040868 W US 2020040868W WO 2021007148 A1 WO2021007148 A1 WO 2021007148A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
coating
phosphor
emitting device
phosphor component
Prior art date
Application number
PCT/US2020/040868
Other languages
English (en)
Inventor
Caroline E. REILLY
Guillaume LHEUREUX
Claude C.A. Weisbuch
Original Assignee
The Regents Of The University Of California
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Regents Of The University Of California filed Critical The Regents Of The University Of California
Publication of WO2021007148A1 publication Critical patent/WO2021007148A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
    • F21V9/20—Dichroic filters, i.e. devices operating on the principle of wave interference to pass specific ranges of wavelengths while cancelling others
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21K—NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
    • F21K9/00—Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
    • F21K9/60—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
    • F21K9/64—Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
    • F21V9/30—Elements containing photoluminescent material distinct from or spaced from the light source
    • F21V9/32—Elements containing photoluminescent material distinct from or spaced from the light source characterised by the arrangement of the photoluminescent material
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/28—Interference filters
    • G02B5/285—Interference filters comprising deposited thin solid films
    • G02B5/288—Interference filters comprising deposited thin solid films comprising at least one thin film resonant cavity, e.g. in bandpass filters
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0087—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for illuminating phosphorescent or fluorescent materials, e.g. using optical arrangements specifically adapted for guiding or shaping laser beams illuminating these materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/0225—Out-coupling of light
    • H01S5/02257—Out-coupling of light using windows, e.g. specially adapted for back-reflecting light to a detector inside the housing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/30—Semiconductor lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0078—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for frequency filtering

Definitions

  • This invention relates to a wavelength selective phosphor converting system for laser lighting devices.
  • This invention discloses an apparatus and a method of fabricating the apparatus by packaging a light-emitting device, such as a laser diode or a light-emitting diode, with a phosphor component optically coupled to the light-emitting device, wherein a coating, such as a distributed Bragg reflector (DBR) or Fabry-Perot (FP) resonator, is applied to the phosphor component, and the coating is minimally reflective and maximally transmissive for one or more wavelengths of light from the light-emitting device, and the coating is maximally reflective and minimally transmissive for one or more wavelengths of light from the phosphor component.
  • a light-emitting device such as a laser diode or a light-emitting diode
  • FP Fabry-Perot
  • the coating is made of one or more layers of dielectric materials with different optical indices, such as silicon dioxide (SiO 2 ) and tantalum pentoxide (Ta 2 O 5 ).
  • the DBR has a structure with one or more repeating quarter-wavelength (l/4) layers, while the FP resonator has a structure with one or more l/4 layers surrounding a central half-wavelength (l/2) cavity.
  • Fig. 1 A is a schematic of an integrated laser lighting system
  • Fig. IB is a photograph of the integrated laser lighting system
  • Fig. 2A is a schematic of a single crystal phosphor with a DBR on its backside
  • Fig. 2B is a schematic of the structure of the DBR with l/4 layers repeating
  • Figs. 2C and 2D are graphs of emission or reflectance vs. wavelength l (nm) for simulations of DBR reflectivity with different period numbers and different maximum wavelength reflectivities, indicating DBR reflectivity in a plot with a triangle marker symbol, laser emission line in a plot with a circle marker symbol, and Ce: YAG phosphor emission spectrum in a plot with a square marker symbol.
  • Figs. 3A, 3B, 3C and 3D are transfer matrix simulations of the reflection coefficient at the phosphor/air interface, wherein Fig. 3 A is a graph of Reflection (R) coefficient vs. angle (degree) at normal incidence; Fig. 3B is a graph of the mean R coefficient as a function of wavelength and angle; Fig. 3C is a graph of the R coefficient vs. wavelength (nm) at the phosphor/DBR interface, at normal incidence of a beam coming from the phosphor, with the emission spectra of the phosphor compound overlaid; and Fig. 3D is a graph of the mean R coefficient of a beam coming from the phosphor with the DBR present as a function of wavelength and angle.
  • R Reflection
  • Fig. 3B is a graph of the mean R coefficient as a function of wavelength and angle
  • Fig. 3C is a graph of the R coefficient vs. wavelength (nm) at the phosphor/DBR interface, at normal
  • Fig. 4A is a schematic of a single crystal phosphor with an FP resonator on its backside
  • Fig. 4B is a schematic of the structure of the FP resonator with l/4 layers surrounding a central l/2 cavity
  • Fig. 4C is a photograph of the backside of phosphor single crystals, after deposition of the FP resonator, that have been diced into triangles approximately 1 mm per side.
  • Fig. 5 is a graph of reflectance or emission vs. wavelength (nm), for simulations for wavelength-selective coatings indicating laser wavelength (442 nm), Ce: YAG phosphor emission, simulated normal reflectivity for a DBR (3-period centered at 570 nm), simulated normal reflectivity for the FP, and experimental reflectivity for the FP.
  • Fig. 6A is a graph of reflectance or emission vs. wavelength l (nm) of spectra collected in an integrating sphere, for emission from the integrated laser lighting system showing phosphor emission for similar thicknesses of single crystal phosphor with and without the FP resonator coatings; and Fig. 6B is a graph of maximum (max) phosphor emission vs. maximum (max) laser light of spectra collected in an integrating sphere, for several phosphors with similar thicknesses with and without FP resonator coatings.
  • Figs. 7 A, 7B and 7C are schematics of phosphors with DBRs on their back surface and with other changes to improve extraction, wherein Fig. 7A shows shaping, Fig. 7B shows a roughened top surface, and Fig. 7C shows both shaping and a roughened top surface.
  • Figs. 8A and 8B are schematics illustrating optical losses in a laser-single crystal phosphor device, wherein Fig. 8A is a schematic without any coating and Fig. 8B is a schematic with a wavelength selective reflective coating represented as alternating layers, such that sources of losses enclosed in the dashed area in Fig. 8A are minimized with the addition of the coating in Fig. 8B.
  • Fig. 9A is a graph of optical efficiency (%) vs. test number and Fig. 9B is a graph of maximum (Max) phosphor intensity vs. maximum (Max) laser intensity, providing comparisons between single crystal Ce: YAG phosphors without and with Fabiy-Perot coatings, wherein Fig. 9A shows the optical efficiency as a function of test number and Fig. 9B shows the maximum phosphor intensity versus the maximum laser intensity.
  • This invention allows for more efficient phosphor-based light-emitting devices.
  • the application of this invention is for a light-emitting device, such as a III-nitride laser diode (LD) or light-emitting diode (LED), in which the emitted light is passed through, and partially converted by, a phosphor component in a transmission geometry.
  • a coating is applied to the phosphor component such that the coating is minimally reflective and maximally transmissive for one or more wavelengths of light from the light-emitting device, and the coating is conversely maximally reflective and minimally transmissive for one or more wavelengths of light from the phosphor component.
  • the amount of light-emitting device light coupled into the phosphor and the amount of phosphor light being projected upwards in the device are both increased. Both effects contribute to an increase in device efficiency.
  • III-nitride “group-III nitride”, or “III-N” refer to any alloy composition of (Ga, Al,In,B)N semiconductors having the formula where 0
  • III-nitride devices may be grown on various planes of the crystal, such as polar, nonpolar and semipolar planes, considering spontaneous and piezoelectric polarization effects of these planes.
  • the phrase“minimally reflective” for one or more wavelengths of light from the light-emitting device is defined as less than 8% reflective; the phrase“maximally transmissive” for one or more wavelengths of light from the light-emitting device is defined as more than 92% transmissive; the phrase“maximally reflective” for one or more wavelengths of light from the phosphor component is defined as more than 60% reflective; and the phrase“minimally transmissive” for one or more wavelengths of light from the phosphor component is defined as less than 40% transmissive.
  • This invention increases the efficiency of phosphor-based light-emitting devices through the use of a wavelength-selective phosphor coating. In one embodiment, this invention increases the efficiency of a single-crystal phosphor-based laser diode lighting package by a significant margin, with testing showing around a 22% increase in efficacy.
  • Solid-state lighting has had success partly due to efficiency and form factor benefits provided by semiconductor lighting devices.
  • White solid-state lighting is dominated by III-nitride LEDs, with laser-based lighting becoming a topic of interest more recently.
  • Laser lighting provides benefits in specific applications, such as high-brightness directional emission. Many LEDs need to be used together to provide the same output power as one laser. By increasing the number of LEDs, the area over which the light is emitted also increases. If directionality is desired, the larger area of emission for LEDs will not be as well focused using lossless optical components as will be the smaller emitting area of a laser. To improve the directionality of the LED system, significant efficiency losses will occur, decreasing the brightness of the system. Laser lighting provides an efficient pathway for spotlight-like applications by providing high brightness over a small emitting area, improving the directionality of the light.
  • Ce: YAG commonly used in blue light to yellow light conversion, where blue light plus yellow light makes white light.
  • the Ce: YAG phosphor has a broad emission spectrum centered in yellow region of the visible spectrum because the Ce: YAG emission also contains significant components beyond yellow into the orange and red portions of the visible spectrum.
  • One possible way to integrate the phosphor and the laser in a single device is the transmission geometry, in which the laser light passes through the phosphor while being partially converted. In this geometry, the laser light reaching the phosphor and the phosphor light emitted upward should be maximized, in particular by avoiding reflection of laser light at the phosphor surface and backward-emitted phosphor light, both of which could be absorbed by the package.
  • Fig. 1 A is a schematic of an integrated light-emitting device 100, including a laser diode 101 emitting light 102 located within a TO-9 can package 103, a copper heat sink 104 with a recess 105 on its back side exposing a cathode 106 and an anode 107 of the laser diode 101, and a phosphor holder 108 holding a phosphor component 109 emitting light 110 and a coating 111, wherein the laser 101 light 102 and the phosphor 109 light 110 may be combined, for example, into white light 112.
  • Fig. IB is a photograph of the integrated light-emitting device 100.
  • the phosphor component 109 may be comprised of a single crystal phosphor, or a phosphor plate, or a phosphor powder in a glass or ceramic matrix, or a phosphor on a substrate, or other forms of phosphor components 109.
  • the reflectivity at the phosphor-air interface is about 8%, such that 8% of the laser 101 light 102 incident normally on the surface of the phosphor component 109 will be reflected back and will be absorbed by the laser 101 and/or its package 103, contributing to the overall losses of the device 100.
  • the single crystal phosphor 109 needs to allow the light 102 to be coupled in from the laser 101 and have high extraction efficiency.
  • a wavelength-selective reflective coating 111 has been implemented to address these concerns, which increases the luminous efficacy of the device 100.
  • Engineering the phosphor component 109 using this concept may allow for single crystal phosphors 109 to be viable options for future laser lighting devices 100. Improvements to this reflectivity can be made through anti-reflection coatings 111, to increase the in-coupling of the laser 101 into the phosphor 109. But, this may lower the efficiency of the device 100, since it will, at the same time, favor the extraction of the light 102 in the backwards direction where it will be absorbed by the package 103. There is a need to selectively reflect the phosphor 109 light 110 upwards in these devices
  • a coating 111 should be wavelength selective to be reflective for the phosphor’s 109 light 110, and transmissive for externally impinging laser’s 101 light 102.
  • One option for this wavelength-selective coating 111 may be a DBR coating 111, which is a design often used for high reflectivity.
  • Another option for the coating 111, which has been experimentally tested by the inventors, is an FP resonator coating 111.
  • Both DBR and FP resonator coatings 111 are made of layers of dielectric materials with different optical indices.
  • the materials used for the coating 111 comprise alternating layers of silicon dioxide ( SiO 2 ) and tantalum pentoxide (Ta 2 O 5 ), although other materials may be used.
  • the idea is to design the thickness and the number of periods of the coating 111 to center the reflectivity maximum around the broad emission of the phosphor 109 and, at the same time, have a reflectivity minimum at the wavelength of the laser 101.
  • a variety of materials may be used as the coating 1 11 layers, with optimization necessary for each coating 111 to tune the minimum and maximum wavelengths to match the laser 101 and phosphor 109 emissions, which may be different for various applications.
  • a coating 111 comprising a DBR
  • alternating SiO 2 and Ta 2 O 5 in l/4 thick layers gives rise to a photonic band gap which results in an optical reflectivity close to 1 for a range of wavelengths. At wavelengths below and above this plateau, the reflectivity of the DBR coating 111 oscillates and can be equal to zero for certain wavelengths.
  • the structure of the DBR coating 111 proposed in this invention is shown in Figs. 2A and 2B, along with reflectivity calculations in Figs. 2C and 2D, and more detailed simulations are given in Figs. 3A, 3B, 3C and 3D.
  • Fig. 2A is a schematic of a single crystal phosphor 109 with a DBR coating 111 on its backside
  • Fig. 2B is a schematic of the structure of the DBR coating 111 with l/4 layers repeating
  • Figs. 2C and 2D are graphs of emission or reflectance vs.
  • wavelength l (nm) for simulations of DBR coating 111 reflectivity labeled with different period numbers (3 period in Fig. 2C and 7 period in Fig. 2D) and different maximum wavelength reflectivities (585 nm in Fig. 2C and 575 nm in Fig. 2D), indicating DBR coating 111 reflectivity in a plot with a triangle marker symbol, laser 101 emission line in a plot with a circle marker symbol, and Ce: YAG phosphor 109 emission spectrum in a plot with a square marker symbol.
  • the thicknesses of the layers are described in terms of optical thicknesses, which correspond to the given material.
  • Figs. 3 A, 3B, 3C and 3D are transfer matrix simulations of the phosphor/air interface (Figs. 3A and 3B) or of the phosphor/DBR interface (Figs. 3C and 3D), with light impinging from the air or phosphor, respectively, wherein Fig. 3A is a graph of the Reflection coefficient vs. angle (degree) at normal incidence; Fig. 3B is a graph of the mean Reflection coefficient as a function of wavelength and angle; Fig. 3C is a graph of the Reflection coefficient vs.
  • Fig. 3D is a graph of the mean Reflection coefficient with the DBR coating 111 of a beam coming from the phosphor 109 as a function of wavelength and angle. The efficient reflection of phosphor 109 light 110 with a wavelength adjusted to the forbidden band of the DBR coating 111 is clearly seen in Fig. 3D for almost all incident light directions.
  • Fig. 4A is a schematic of a single crystal phosphor 109 with a coating 111 comprising an FP resonator on its backside
  • Fig. 4B is a schematic of the structure of the FP resonator coating 111 with l/4 thick layers surrounding a central l/2 thick layer comprising a resonator cavity
  • Fig. 4C is a photograph of the backside of the single crystal phosphor 109 after deposition of the FP resonator coating 111 that has been diced into triangles having dimensions of approximately 1 mm per side.
  • the FP resonator coating 111 can also provide a desirable reflectivity spectrum.
  • the wavelength of the reflectance minimum for a FP resonator coating 111 is broad and largely determined by the l/2 cavity in the center of the FP resonator coating 111. This leads to the minimum being experimentally more controllable than in the case of the DBR coating 111, where the minimum is sharper. While the FP resonator coating 111 is more easily experimentally achievable, a DBR coating 111 that is properly calibrated and deposited would provide both a higher maximum reflectivity and a lower minimum reflectivity. This would lead to a greater overall device 100 efficiency improvement in the case of the DBR coating 111.
  • the FP resonator coating 111 detailed in Figs. 4A, 4B and 4C was deposited onto a single crystal Ce: YAG phosphor 109.
  • the thickness of the phosphor 109 can be varied to optimize the color point of the device 100.
  • the phosphor 109 was thinned and polished using chemical mechanical polishing (CMP) to achieve an optically flat surface for deposition.
  • CMP chemical mechanical polishing
  • the FP resonator coating 111 was deposited used ion beam deposition (IBD), but could be deposited using other methods.
  • DBR coating 111 was 570 nm with three periods, and the target wavelength minimum for the FP resonator coating 111 was 442 nm to match the experimental wavelength of a laser 101 initially tested.
  • the FP resonator coating 111 in Figs. 4A and 4B was deposited on a polished Ce:YAG single crystal phosphor 109 using ion beam deposition. Layer thicknesses and refractive indices were calibrated using ellipsometry and the overall FP resonator coating 111 was calibrated by iterating on depositions and adjusting layer thicknesses. Using a similar method, the deposition of a DBR coating 111 was also attempted.
  • the FP resonator coating 111 could be calibrated to have a minimum at the laser 101 wavelength
  • the DBR coating 111 was calibrated with respect to the wavelength of maximum reflectance. The fringes and minima were then heavily dependent on precise control of deposition rates and refractive indices, such that a DBR coating 111 with a minimum at the laser 101 wavelength was difficult to achieve and not reported herein.
  • Normal reflectivity measurements were measured on reference polished sapphire pieces and on the final FP resonator coating 111 deposited on the single crystal phosphor 109 from the backside of the phosphor 109, given in Fig. 5.
  • the theoretical minimum reflectivity was 1.2%, whereas the experimentally achieved minimum value was ⁇ 3%.
  • Figs. 6A and 6B show the difference in phosphor 109 emission from several tests, as well as the comparison of the maximum of the phosphor 109 emission to the maximum of the laser 101 emission.
  • Fig. 6A is a graph of reflectance or emission vs. wavelength l (nm), of spectra collected in an integrating sphere, for emission from the integrated laser lighting device 100 showing phosphor 109 emission for similar thicknesses of single crystal phosphor 109 with and without FP resonator coatings 111; and
  • Fig. 6B is a graph of maximum (max) phosphor 109 emission vs.
  • Figs. 7A, 7B and 7C are schematics of phosphors 109 with DBR coatings 111 on a back surface of the phosphors 109, wherein Fig. 7A shows shaping of the phosphor 109 to improve extraction, Fig. 7B shows a roughened top surface of the phosphor 109 to improve extraction, and Fig. 7C shows both shaping and a roughened top surface of the phosphor 109 to improve extraction.
  • the phosphor material typically encases the LED where adding the encapsulant improves the out-coupling from the LED.
  • the phosphor component 109 does not encase the laser 101, resulting in some losses.
  • Fig. 8 A Some sources of loss are depicted in Fig. 8 A.
  • One source of loss is due to the reflection of the laser 101 light 102 at the surface of the phosphor 109, as shown in the dashed area 800. Any amount of laser 101 light 102 that gets reflected back by the phosphor 109 surface is lost due to absorption by the package 103, heat sink 104, or phosphor holder 108.
  • the percentage of incoming light 102 reflected at normal incidence for a phosphor 109 with an optically smooth interface was calculated to be 8.5%.
  • This loss can be reduced by the addition of an antireflective (AR) coating such as a quarter-wavelength coating 111 tuned for the laser 101 light 102 wavelength. While an AR coating would serve to help with the laser 101 in-coupling efficiency, it may also serve to increase the amount of yellow light 110 extracted out of the bottom of the phosphor 109. In the transmission geometry, yellow phosphor 109 light 110 extracted in the downwards direction towards the laser 101 would be another source of loss due to absorption by the package 103, heat sink 104, or phosphor holder 108, as shown in the dashed area 800. A coating 111 that is reflective in the yellow range and transmissive in the blue range is therefore desired. As indicated in Fig.
  • AR antireflective
  • this coating 111 could minimize incoupling losses as well as losses due to downward reflection of yellow light 110, as shown in the dashed area 800.
  • Such a coating 111 could take the form of a DBR or FP resonator coating 111, either of which would be designed to have wavelength dependent reflectivity over the visible wavelength range.
  • the DBR coating 111 with the structure shown in in Figs. 2A and 2B, and the FP resonator coating 111 with the structure shown in Figs. 4A and 4B, are two examples of potential coatings 111.
  • the optical thicknesses of the thinner layers are l/4 thick, while the resonant Ta 2 O 5 cavity was l/2 thick in the FP resonator coating 111.
  • the SiO 2 side was in contact with the single crystal phosphor 109 for both of the DBR coating 111 and the FP resonator coating 111.
  • the choice of dielectric material and periodicity was not unique, as a variety of designs may achieve varying levels of reflectivity.
  • a series of phosphors 109 was then tested with and without the presence of a FP resonator coating 111, in order to provide an initial demonstration of the coating 111 technology presented.
  • a single crystal phosphor 109 with an FP resonator coating 1 11 was diced into triangles ( ⁇ 1 mm per side, 800 mm thick) and the diced phosphors 109 were compared to a set of uncoated single crystal phosphors 109 ( ⁇ 1 mm per side, 850 mm thick), where all phosphors 109 had the same equilateral triangle shape and side length.
  • the marginally thicker phosphor 109 was used as the uncoated sample so that any increase in phosphor 109 extraction provided by the FP resonator coating 111 could be attributed to the coating 111 and not to the thickness difference.
  • Ten tests were conducted in which the laser 101 was tested alone, followed by testing of an uncoated sample, followed by a sample with the FP resonator coating 111. The compact setup was utilized in each case.
  • the wall plug efficiency (WPE) of the laser 101 as tested before the phosphors 109 was considered the WPE of the laser 101 during the phosphor 109 test in order to consider laser 101 fluctuations.
  • the relative optical efficiency (OE) of the device 100 was estimated based on the Equation set forth below, wherein QY is the quantum yield of the phosphor 109, SS is the Stokes Shift of the phosphor 109 conversion, and LER is the luminous efficacy of radiation, with the QY of the phosphor 109 and the SS of the phosphor 109 conversion assumed to be 90% and 78%, respectively.
  • the Equation does not consider that the QY and SS only apply to the laser 101 light 102 being absorbed and converted by the phosphor 109, respectively, the relative estimation for OE should be comparable sample to sample.
  • the average efficacy, LER, and OE were all greater in the samples with the FP resonator coating 1 1 1.
  • the average efficacy increased by 22% with the addition of the FP resonator coating 111.
  • Fig. 9A compares the OE of each sample over the order of testing the samples, showing that effects from any deviations in the laser 101 power were mitigated.
  • the average relative OE was 45% and 52% for the samples without and with the FP resonator coating 111, respectively.
  • the improvement in OE with the addition of the FP resonator coating 111 was attributed to better in-coupling of the laser 101 , as well as better extraction of the phosphor 109 light 110.
  • Fig. 9B shows a comparison in the maximum of the phosphor 109 peak and the maximum of the laser 101 peak.
  • the phosphors 109 with the coating 111 had more phosphor 109 emission for a given laser 101 peak height. This led to the increase in LER with the introduction of the FP resonator coating 111, as the yellow phosphor 109 light 110 overlaps more with the eye response function than the blue laser 101 light 102.
  • the average LER without the coating 111 was 364 lm/W and with the FP resonator coating 111 was 385 lm/W.
  • the increase in LER also suggests that the use of the FP resonator coating 111 can allow for less phosphor component 109 to be used in order to achieve the desired white light 112 point
  • the increase in LER with the increase in OE together form the basis for the reported increase in luminous efficacy in the device 100.
  • Edge-emitting lasers, VCSELs, or other types of light emitters may be used, with different wavelengths than blue, eventually in addition to blue lasers, VCSELs, or other types of light emitters.
  • Lasers may be incorporated as packaged devices, such as the example of the TO-9 can laser, or may be incorporated into the device as a laser bar with packaging encasing the phosphor.
  • DBR or FP resonator materials may be used, as well as different deposition techniques and various precursors.
  • the invention can be modeled and tuned over any wavelength range of lasers and/or phosphors with proper simulations, calibrations, and deposition techniques.
  • the invention can be used with types of phosphor other than Ce: YAG.
  • Multiple phosphors and/or multiple lasers with different wavelengths of emission can be used.
  • the invention can be used for laser diodes of varied wavelengths, including ultraviolet (UV), blue, green, or red lasers, as well as LEDs.
  • UV ultraviolet
  • blue green
  • red lasers as well as LEDs.
  • This invention can be used for types of phosphors other than single crystal, including but not limited to ceramics.
  • the invention may be comprised of multiple phosphors incorporated as powders, layers of single-crystal phosphors, ceramics, deposited in a sol-gel, or other ways.
  • the invention may be employed to tune the color point of the device by altering the ratios of various wavelengths escaping the device by a proper design of the multilayer coating (beyond the simple DBR or FP resonator designs).
  • This invention can decrease the amount of phosphor material necessary to achieve a desired color point
  • This invention may apply in cases where the laser and phosphor are spatially separated and/or separated by other optical elements.
  • This invention could be applied to other form factors, including designs in which lasers are coupled into fibers and then converted into white light by a phosphor at the output of the fiber, or phosphor shaped as fiber.
  • the frequency selective coatings described here should be seen as a general coating with wavelength selective functionality.
  • One of skill in the art would know how to produce any desired spectral optical transmission or reflection coefficient by the association of multilayers of different indices and thicknesses, such as the Rugate or the dichroic filters, but not limited to these designs.
  • the invention reported here describes the general use of a coating highly transmissive of incoming light onto a phosphor and highly reflective of the phosphor emitted light.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Engineering & Computer Science (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Semiconductor Lasers (AREA)

Abstract

L'invention concerne un dispositif, un procédé de fabrication du dispositif et un procédé de génération de lumière à partir du dispositif, par encapsulation d'une diode laser au nitrure III avec un composant phosphore couplé optiquement à la diode laser, un revêtement, tel qu'un réflecteur de Bragg distribué (DBR) ou un résonateur de Fabry-Prévot (FP), étant appliqué sur le composant phosphore et le revêtement étant réfléchissant au minimum et transmissif au maximum pour une ou plusieurs longueurs d'onde de lumière provenant de la diode laser et le revêtement étant réfléchissant au maximum et transmissif au minimum pour une ou plusieurs longueurs d'onde de lumière provenant du composant phosphore. Le revêtement est constitué d'une ou plusieurs couches de matériaux diélectriques ayant différents indices optiques, tels que le dioxyde de silicium (SiO2) et du pentoxyde de tantale (Ta2O 5 ). Le DBR a une structure avec une ou plusieurs couches de quart d'onde de répétition (λ/4), tandis que le résonateur FP a une structure avec une ou plusieurs couches ?/4 entourant une cavité de demi-longueur d'onde centrale (λ/2).
PCT/US2020/040868 2019-07-05 2020-07-06 Système de conversion de phosphore sélectif en longueur d'onde pour dispositifs d'éclairage laser WO2021007148A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201962870900P 2019-07-05 2019-07-05
US62/870,900 2019-07-05

Publications (1)

Publication Number Publication Date
WO2021007148A1 true WO2021007148A1 (fr) 2021-01-14

Family

ID=74114322

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2020/040868 WO2021007148A1 (fr) 2019-07-05 2020-07-06 Système de conversion de phosphore sélectif en longueur d'onde pour dispositifs d'éclairage laser

Country Status (1)

Country Link
WO (1) WO2021007148A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6155699A (en) * 1999-03-15 2000-12-05 Agilent Technologies, Inc. Efficient phosphor-conversion led structure
US20120162380A1 (en) * 2010-12-28 2012-06-28 Gwangju Institute Of Science And Technology Optical modulator using multiple fabry-perot resonant modes and apparatus for capturing 3d image including the optical modulator
US8324647B2 (en) * 2008-01-28 2012-12-04 Photonstar Led Limited Light emitting module with optically-transparent thermally-conductive element
US8492863B2 (en) * 2010-01-22 2013-07-23 Samsung Electronics Co., Ltd. Optical modulator
US20140126200A1 (en) * 2008-08-05 2014-05-08 The Regents Of The University Of California White light source employing a iii-nitride based laser diode pumping a phosphor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6155699A (en) * 1999-03-15 2000-12-05 Agilent Technologies, Inc. Efficient phosphor-conversion led structure
US8324647B2 (en) * 2008-01-28 2012-12-04 Photonstar Led Limited Light emitting module with optically-transparent thermally-conductive element
US20140126200A1 (en) * 2008-08-05 2014-05-08 The Regents Of The University Of California White light source employing a iii-nitride based laser diode pumping a phosphor
US8492863B2 (en) * 2010-01-22 2013-07-23 Samsung Electronics Co., Ltd. Optical modulator
US20120162380A1 (en) * 2010-12-28 2012-06-28 Gwangju Institute Of Science And Technology Optical modulator using multiple fabry-perot resonant modes and apparatus for capturing 3d image including the optical modulator

Similar Documents

Publication Publication Date Title
TWI787152B (zh) 具有反射側塗層之發光裝置
TWI569549B (zh) 雷射結構、半導體雷射結構、及操作雷射結構的方法
US11393949B2 (en) Semiconductor component and illumination device
US8324647B2 (en) Light emitting module with optically-transparent thermally-conductive element
JP2015523722A (ja) 遠隔蛍光体ｌｅｄと直接放射ｌｅｄの組合せを使用するハイブリッド電球
KR20150134312A (ko) 단열 평판형 도파로 커플러 변환기
JP2010532104A (ja) 高効率白色発光ダイオードのための光学設計
TW201017863A (en) Semiconductor color-tunable broadband light sources and full-color microdisplays
KR20160117696A (ko) 발광 소자
WO2013125214A1 (fr) Élément électroluminescent semi-conducteur
WO2015112943A1 (fr) Dispositif à del à réflecteur de bragg et procédé de découpage de substrats de tranche de del en dés le comportant
TW202117864A (zh) 使用二向分色反射鏡的垂直腔表面發射雷射
JP2022088580A (ja) 放射放出半導体デバイス
KR20110059616A (ko) 광추출이 향상된 인버터 ｌｅｄ구조
TW565975B (en) Oxide confined type vertical cavity surface emitting laser device and the manufacturing method thereof
WO2021007148A1 (fr) Système de conversion de phosphore sélectif en longueur d'onde pour dispositifs d'éclairage laser
JP2014510411A (ja) 半導体チップ、複数の半導体チップを備えたディスプレイ、およびそれらの製造方法
US7492802B2 (en) End pumping vertical external cavity surface emitting laser apparatus
RU2461932C2 (ru) Полупроводниковый дисковый лазер
JP7125720B2 (ja) 半導体発光素子
Reilly et al. Transmission geometry laser lighting with a compact emitter
US20230155058A1 (en) Optoelectronic Component
JP2005197650A (ja) 発光素子
US20200142209A1 (en) Aperiodic Nano-Optical Array for Angular Shaping of Incoherent Emissions
JP7357082B2 (ja) 光学装置および光学装置の製造方法

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20837300

Country of ref document: EP

Kind code of ref document: A1

122 Ep: pct application non-entry in european phase

Ref document number: 20837300

Country of ref document: EP

Kind code of ref document: A1