CN110301075B - Optical transmitter based on grating - Google Patents

Abstract

A grating-based optical transmitter includes a light source region coupled to an interference region, two reflective regions on either side of the interference region, and one or more gratings that interact with interfering light waves in the interference region to cause vertical emission. Two electrodes are used to inject electrical carriers and a third electrode may be added to modulate the electrical carrier density that recombines in the light source region. The grating-based optical transmitter of the present invention greatly reduces packaging cost and complexity due to vertical emission and greatly increases modulation bandwidth due to the three-terminal configuration, as compared to conventional edge-emitting lasers with two electrodes.

Description

Optical transmitter based on grating

Cross Reference to Related Applications

This application claims the priority of united states patent application No.15/201,907 entitled "marking Based Optical Transmitter" filed on 5.7.2016, the application No.15/201,907 being a continuation-in-part application of united states patent application No.14/291,253 entitled "Optical Device for Redirecting imaging electric Wave" filed on 30.5.2014, whereas the application No.14/291,253 claims the priority of united states provisional patent application No.61/979,489 filed on 14.4.2014, united states provisional patent application No.61/925,629 filed on 9.1.9.2014, and united states provisional patent application No.61/895,493 filed on 25.10.25.25.2013, which are incorporated herein by reference.

This specification is also a continuation-in-part application to U.S. patent application No.14/964,865 entitled "grading Based Optical Coupler" filed on 12/10/2015, application No.14/964,865 is U.S. patent application No.14/510,799 filed on 10/9/2014, now a continuation of U.S. patent No.9,239,507, which patent No.9,239,507 claims U.S. provisional patent application No.62/014,182 filed on 19/2014, U.S. provisional patent application No.62/012,446 filed on 16/2014, U.S. provisional patent application No.61/979,489 filed on 14/2014 4/2014, U.S. provisional patent application No.81/946,657 filed on 28/2014, U.S. provisional patent application No.61/925,629 filed on 9/2014, and U.S. provisional patent application No.61/895,493 filed on 25/10/2013, which are incorporated herein by reference.

This specification is also a continuation-in-part application to U.S. patent application No.14/635,133 entitled "tuning BASED option translator" filed 3/2/2015, which application No.14/635,133 claims priority to U.S. provisional patent application No.62/014,182 filed 6/19/2014, U.S. provisional patent application No.62/012,446 filed 6/16/2014, U.S. provisional patent application No.61/979,489 filed 4/14/2014, and U.S. provisional patent application No.61/946,657 filed 2/28/2014, which are incorporated herein by reference.

This specification also claims priority from U.S. provisional patent application 62/194,170 filed on 7/17/2015, which is incorporated herein by reference.

Technical Field

This description relates to coupling light using gratings.

Background

Light propagates within the photonic integrated circuit and is coupled to an external medium through a grating fabricated on the photonic integrated circuit. Traditionally, coupling between light and photonic integrated circuits is achieved by edge coupling, where the optical surface needs to be prepared and the process is time consuming and expensive. The emission of a laser diode in a photonic integrated circuit is coupled to an external medium through a grating. The two terminals of the laser diode are used to inject electrical carriers to generate photons, and the photons resonate in the cavity and emit coherent light.

Disclosure of Invention

In accordance with one innovative aspect of the subject matter described in this specification, an optical device includes: a light source region configured to generate light; first and second reflective regions configured to reflect the generated light such that interference light is formed in a first direction; an interference region formed between the first and second reflective regions and coupled to the light source region, and configured to confine at least a portion of interference light formed in the first direction by light reflected between the first and second reflective regions; and a grating region including first and second grating structures having substantially the same period but different duty cycles, wherein both grating structures are arranged with a 180 ° phase shift along the first direction, wherein the grating region is formed on a region that confines at least a portion of the interfering light, and the grating region is configured to emit at least a portion of the light along a second direction different from the first direction.

This and other embodiments may each optionally include one or more of the following features. The grating periodicity of the first grating structure may substantially match the periodicity of the interfering light within the interference region. A quarter-wave shift region may be formed in the grating region by removing or adding at least one section of the grating structure. A tapered region may be formed adjacent to the quarter-wavelength shift region along the first direction, wherein a period or duty cycle of the tapered region increases or decreases from a side closer to the quarter-wavelength shift region toward a side away from the quarter-wavelength shift region.

The first reflective region may be a surface corrugated grating structure forming distributed feedback or distributed bragg reflection. The duty cycle of the first grating structure of the grating region may be different from the duty cycle of the surface corrugated grating structure of the first reflective region, and the period of the first grating structure is twice the period of the surface corrugated grating structure. The first grating structure of the grating region may be formed on the same plane as the surface corrugated grating structure of the first reflection region.

The light source may be at least partially embedded in the interference region and may comprise alternating III-V material layers forming quantum wells or quantum wire or quantum dot structures. A portion of the grating region may be formed on the interference region or the first reflective region. The second direction may be substantially perpendicular to the first direction. The first grating structure region may have a grating period of d2, wherein the intensity period of the interfering light within the interference region may be d1, wherein d2 is substantially equal to 2 × d 1.

The grating region may have a grating length in the first direction and a grating width in a third direction perpendicular to the first direction on a plane, and the grating width may be different from the grating length to obtain a circular beam profile (beam profile).

The optical device may include an n-doped region and a p-doped region configured to provide an electric field in the interference region by applying a voltage or current across the n-doped region and the p-doped region, wherein the interference region is configured to provide different interference patterns for the interference light by applying a voltage or current across the n-doped region and the p-doped region.

The optical device may comprise an n-doped region and a p-doped region configured to provide an electric field in the first and/or second reflective region by applying a voltage or current across the n-doped region and the p-doped region, wherein the first and/or second reflective region is configured to provide different reflectivities by applying a voltage or current across the n-doped region and the p-doped region.

The first reflective region or the second reflective region may include one of: corner mirror, DBR mirror, DFB mirror, anomalous dispersion mirror, waveguide ring mirror, dielectric layer with metal mirror, metal layer. The grating regions may be formed with lattice vectors such that the positions of in-phase antinodes of the interfering light within the interference region substantially match the positions of grating valleys or peaks.

The optical device may include first and second electrodes electrically coupled to the light source region, the first and second electrodes configured to generate light through electrical carrier injection using an electric field applied between the first and second electrodes. The optical device may include a third electrode electrically coupled to the light source region, the third electrode being configured to modulate an electrical carrier concentration in the light source region by an electric field applied between (i) the first electrode and the third electrode or (ii) the second electrode and the third electrode.

The light source region may include at least two different material layers, and the first electrode and the third electrode are in physical contact with the different material layers of the light source region. A dielectric layer may be formed between the third electrode and the light source region, and the third electrode is configured to modulate an amount of electric carriers recombined in the light source region by a capacitive effect without injecting the electric carriers into the light source region. At least two different voltage levels may be applied sequentially to the third electrode to modulate the amount of electrical carriers that recombine in the light source region to obtain different output optical power levels.

The grating region and the third electrode may be located on opposite sides of the interference region, and the light is emitted through the side of the grating region. The grating region and the third electrode may be located on opposite sides of the interference region, and the light is emitted through the opposite side of the grating region. The grating region and the third electrode may be located on the same side of the interference region, and the light is emitted through the side of the grating region. The grating region and the third electrode may be located on the same side of the interference region and the light is emitted through the opposite side of the grating region. According to another innovative aspect of the subject matter described in this specification, in which at least a portion of the third electrode can be transparent to light emitted through the side of the grating region, a method for forming an optical transmitter comprising: forming a light source region; forming an interference region, a first reflective region and a second reflective region, wherein the light source region is defined by the first and second reflective regions at two opposing ends along a first direction by the at least partially embedded interference region; and

forming a grating region comprising a first grating structure covering at least a portion of the interference region, wherein a periodicity of the first grating structure substantially matches a period of interfering light along a first direction, wherein light generated by electrical carrier recombination resonates within the interference region along the first direction and exits the interference region along a second direction different from the first direction.

This and other embodiments may each optionally include one or more of the following features. The grating region may include a second grating structure having the same periodicity as the first grating structure but a different duty cycle and a third grating structure that is a surface wave corrugated structure forming a DFB type reflection region. The method may comprise forming a quarter-wavelength shift region in the grating region by removing or adding at least one section of the grating structure. The method may comprise forming a tapered region adjacent the quarter wavelength shift region along the first direction, wherein the period or duty cycle of the tapered region increases or decreases from a side closer to the quarter wavelength shift region towards a side further from the quarter wavelength shift region. The method may comprise forming at least three electrodes electrically coupled to the light source region, wherein the three electrodes are arranged to provide control of a relative electric field between the three electrodes to modulate an electrical carrier concentration within the light source region, and one of the electrodes is an insulated electrode without electrical carrier injection.

Advantageous implementations may include one or more of the following features. Light may be coupled into or emitted from the photonic integrated circuit at an angle that is substantially perpendicular to a direction of propagation of the light within the photonic integrated circuit. This perpendicularity can reduce packaging cost and complexity. Reflected light returning to the photonic integrated circuit may be minimized by one or more mirrors in the interference region to maintain stability of the photonic integrated circuit. The optical mode field distribution of the light exiting the grating can be shaped to match the optical mode field distribution of the external medium to minimize mode field matching losses. Because the electric field in the interference region is very uniform, a chirped grating is not required to match the field distribution of the traveling wave induced exponential decay. The interference region or grating may be actively tuned by mechanisms including electric fields, magnetic fields, or mechanical motion to control the coupling of light. When the interference region is coupled to an active medium that produces a wide range of wavelengths of light, the interference region can be used to select a narrower range of wavelengths from the wide range of wavelengths. When the interference zone is coupled to an absorbing medium that detects light, the interference zone may be used to increase the absorption efficiency by multiple reflections within the interference zone.

Other embodiments of this and other aspects include corresponding systems, apparatus, and computer programs configured to perform the actions of the methods encoded on computer storage devices. A system of one or more computers may be configured by software, firmware, hardware, or a combination thereof installed on the system such that the system performs actions. One or more computer programs may be so configured by having instructions which, when executed by data processing apparatus, cause the apparatus to perform actions.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other potential features and advantages will become apparent from the description, the drawings, and the claims.

Drawings

FIG. 1A is a block diagram of an exemplary photonic integrated circuit;

FIGS. 1B,1C and 1D are examples of optical couplers;

FIG. 2 is an example of an interference pattern;

3A-3E illustrate examples of raster patterns;

4A-4L illustrate examples of optical couplers integrated with light sources;

fig. 5A-5K show block diagrams of grating-based laser devices.

Fig. 6A-6G illustrate examples of grating-based laser devices with front-side modulation.

Figures 7A-7C illustrate examples of grating-based laser devices with back-side modulation.

Fig. 8A shows simulation results of near-field and far-field distributions of a grating-based laser device.

Fig. 8B shows a simulation of the effect of changing the W/L ratio of the waveguide on the beam shape/distribution.

FIG. 9 shows an example of an optical coupler integrated with a p-n junction.

Fig. 10A-10B illustrate examples of optical couplers having multiple output paths.

Figures 11A-11E show examples of mirrors,

figure 12 shows an example of a flow chart for designing a grating-based optical transmitter,

fig. 13 shows an example of a flow chart for manufacturing a grating-based optical transmitter.

Fig. 14A shows a block assembly of a first embodiment of an optical device for redirecting incident light.

Fig. 14B shows a block assembly of a second embodiment of an optical device for redirecting incident light.

FIG. 15A shows a working example further illustrating the embodiment shown in FIG. 14A.

FIG. 15B shows a working example further illustrating the embodiment shown in FIG. 14B.

FIG. 15C shows another working example further illustrating the embodiment shown in FIG. 14B.

Fig. 16A to 16H illustrate block assemblies of exemplary embodiments of optical devices for redirecting incident light.

Fig. 17A to 17E show top views of exemplary embodiments of grating structures 1420.

Fig. 17F to 17J show respective cross-sectional views of exemplary embodiments of the grating structure in fig. 17A to 17E.

Fig. 18A-18C show simplified perspective views of exemplary embodiments of optical devices to further illustrate light redirection paths.

Fig. 19A to 19B are used to illustrate the optical track in the restriction condition with two mirrors.

Like reference numbers and designations in the various drawings indicate like elements. It should also be understood that the various exemplary embodiments shown in the figures are merely illustrative representations and are not necessarily drawn to scale.

Detailed Description

Fig. 1A is a block diagram of an exemplary photonic integrated circuit 100, the photonic integrated circuit 100 including a grating-based optical coupler for enabling coupling of light into and out of the photonic integrated circuit 100. Generally, an optical coupler with substantially vertical transmission is used to connect surface emitting/receiving optoelectronic devices, and may reduce packaging cost and complexity due to improper configuration. Furthermore, surface emitting devices can be characterized at the wafer level without the need to cut and polish the chip, thus reducing overall test and packaging costs as compared to edge emitting devices.

The photonic integrated circuit 100 includes one or more optical components fabricated on a substrate 18. The optical assembly includes a waveguide region 102, a first reflective region 106, an interference region 110, a second reflective region 114, and a grating region 120. The substrate 116 may be any type of substrate suitable for fabricating photonic integrated circuits. For example, the substrate 118 may be a silicon wafer, a silicon-on-insulator (SOI) wafer, a III-V semiconductor such as gallium arsenide (GaAs), an indium phosphide (InP) wafer, or a glass wafer. As another example, the substrate 118 may be a layer of passive or active material deposited on the integrated electronic circuit. As another example, the substrate 116 may be a layer of passive or active material deposited on another integrated photonic circuit.

In general, waveguide region 102 is configured to confine light in one or more dimensions to guide light in a particular direction. In some embodiments, the waveguide region 02 may confine light along one dimension. For example, waveguide region 102 may be a slab waveguide that confines light along the z-direction. In some embodiments, waveguide region 102 may confine light in two dimensions. For example, waveguide region 102 may be a ridge waveguide or channel waveguide that confines light in the y and z directions so that light may propagate in the x direction, as indicated by arrow 122. The term "along the x-direction" and derivatives thereof as used herein may be used to denote bi-directional (± x-direction) or uni-directional (+ x, -x). Furthermore, when light travels inside a multimode waveguide placed along the x-direction, some portion of the light may propagate in a zigzag path within the waveguide while the entire direction may still be considered along the x-direction.

Generally, the first reflective region 106 and the second reflector 114 are configured to reflect incident light. For example, when light in waveguide region 102 is incident on interface 104, a portion of the light may be reflected back into waveguide region 102, while the remaining light may be transmitted to first reflective region 106. Similarly, when light in first reflective region 106 is incident on interface 108, a portion of the light may be reflected and the remaining portion of the light may be transmitted to interference region 110. Similarly, when light in the interference region 110 is incident on the interface 12, a portion of the light may be reflected, and the remaining portion may be transmitted to the second reflective region 114. In some embodiments, the reflector may be an interface between two media having different refractive indices.

The portion of light reflected by the reflector may range from near zero percent to near one hundred percent, depending on the design, and in some embodiments, the first reflective region 08 or the second reflector 114 may be highly reflective. For example, the second reflector 114 may be coated with a metal, such as aluminum, to achieve high reflectivity. As another example, light may be arranged to be incident on the second reflector 14 beyond a critical angle, wherein the light is reflected by total internal reflection. As another example, the second reflector 114 may be a bragg reflector that provides high reflectivity over a range of wavelengths. As another example, first reflective region 106 may include one or more slits that break waveguide region 102 and interference region 110. As another example, the first reflective region 106 may include a DBR structure.

In some embodiments, the first reflective region 106 or the second reflective region 114 can be partially transmissive and partially reflective. For example, the first reflective region 106 may be configured to (i) reflect a portion of incident light by a particular reflectivity, and (ii) transmit another portion of incident light. For example, a partially reflective reflector may be implemented by depositing a dielectric material having a lower refractive index than the material of the waveguide region 102 in the corresponding reflective region. The percentage of reflected and transmitted light can be calculated using the fresnel equation.

Generally, the interference region 110 acts as a waveA cavity length L formed between the guide region 102 and the second reflective region 114_CavityOf the chamber (c). In some embodiments, first reflective region 106 may be formed between waveguide region 102 and interference region 110, where L_CavityMay be defined as the length between the first reflective region 106 and the second reflective region 114. In some embodiments, the effective index of waveguide region 102 may be substantially equal to the effective index of interference region 110. For example, both waveguide region 102 and interference region 110 may be fabricated from silicon having the same cross-sectional waveguide dimensions along the y-z dimension. In this case, the effective index of waveguide region 102 is equal to the effective index of interference region 110. As another example, both waveguide region 102 and interference region 110 may be fabricated from silicon, but the cross-sectional waveguide dimensions along the y-z dimension may vary, which may result in a difference between the effective index of waveguide region 102 and the effective index of interference region 10. In this case, the effective refractive index of waveguide region 102 is considered to be based on being equal to the effective refractive index of interference region 10, as long as the resulting performance degradation, such as optical loss, caused by the effective refractive index difference is within an acceptable range for the target application.

The interference zone 110 is configured to confine interference light formed by the incident light and the reflected incident light. For example, a standing wave pattern between the first reflector 106 and the second reflector 114 can be formed at the interference region 110. To create interference in the interference zone 110, the cavity length L is selected_cavityAnd grating region 120 such that incident light may reach second reflector 114 and be reflected by second reflector 114 without being completely attenuated in the first path from first reflector 08 to second reflector 14. In some embodiments, the confinement may be a partial confinement, wherein a portion of the interference light is transmitted back to the waveguide region 102 by the first reflector 106 and/or a portion of the interference light is transmitted by the second reflector 114. The interference of light formed by incident light and reflected incident light is described in more detail in fig. 2.

In some embodiments, the optical path length of the interference region 110 may be longer than the wavelength of the guided light. In some other embodiments, the optical path length of the interference region 110 may be shorter than the wavelength of the guided light. For example, for an interference region 110 composed of silicon having a cavity length of 0.4 μm and a refractive index of 3.45, the optical path length of the interference region 110 is 0.4 μm × 3.45 — 1.38 μm. If the wavelength of the guided light has a wavelength of 1.55 μm, the optical path length of the interference region 110 is shorter than the wavelength of the guided light. In this case, light having a wavelength of 1.55 μm can be coupled to grating region 120 through an evanescent field (evanescent field) that confines (partially confines) the light in interference region 110.

Typically, having a grating length L_GratingIs configured to optically couple at least a portion of photonic integrated circuit 100 to external medium 130 or to optically couple at least a portion from external medium 130 to photonic integrated circuit 100. In some embodiments, the grating length L_GratingMay be shorter than the cavity length L_Cavity. In some other embodiments, the grating length L_GratingMay be equal to the cavity length L_Cavity. In some other embodiments, the grating length L_GratingCan be longer than the cavity length L_Cavity. For example, grating region 120 can be fabricated on interference region 110, but a portion of grating region 120 can extend into first and/or second reflective regions 108, 114 and/or waveguide region 102. As used herein, forming or fabricating a grating on a region means forming the grating over the region, or at least partially embedding the grating within the region. For example, the grating may be formed by etching into the region on which the grating is disposed.

In some embodiments, interference region 10 and grating region 120 may have the same material composition. For example, grating region 120 can be fabricated by etching a grating pattern directly on the surface of interference region 110. In some other embodiments, the interference region and the grating region may have different material compositions. Grating region 120 may be fabricated, for example, by depositing silicon dioxide on the surface of silicon-based interference region 110. The grating pattern may then be etched on the surface of the silicon dioxide to form an oxide grating. As another example, grating region 120 may be fabricated by depositing metal on the surface of interference region 110 and then etched to form a metal grating. As another example, grating region 120 may be fabricated by depositing a higher index material on the surface of interference region 110 having a lower index of refraction to improve grating efficiency by attracting optical modes toward the grating side. The lower index material may be, for example, InP and the higher index material may be, for example, Si.

In general, grating region 120 redirects light traveling in a first direction to a second direction different from the first direction. In some embodiments, grating region 120 may redirect light propagating along a first direction to a second direction substantially perpendicular to the first direction. For example, by substantially matching the grating periodicity of grating region 120 to the interference periodicity in interference region 110, grating region 120 can redirect light propagating within waveguide region 102 in the x-direction, as shown by arrow 122, to a perpendicular direction in the z-direction, as shown by arrow 123. The term "substantially matched" as used in this application refers to the resulting performance degradation due to mismatch, such as optical loss, being within an acceptable range for the target application. The acceptable range may be, for example, an order of magnitude. In some other embodiments, grating region 120 may redirect light propagating along a first direction to a second direction that is substantially non-perpendicular to the first direction. The term "substantially perpendicular" as used in this application refers to 90 ° with an acceptable margin of error for the target application.

The external medium 130 may be any medium that can transmit, direct, detect, or generate light. For example, the external medium 130 may be an optical fiber. As another example, the external medium 130 may be a photodetector. As another example, the external medium 30 may be a light source. In some embodiments, cladding layer 124 may be formed between grating region 120 and external medium 130. Cladding layer 124 may be formed to protect photonic integrated circuit 00 or to provide a certain distance between grating region 120 and external medium 130. In some embodiments, the cross-sectional mode profile of light emitted from grating region 120 can be designed to substantially match the cross-sectional mode profile of external medium 130 configured to receive light emitted from the grating region. For example, in the x-y dimension, the cross-sectional mode profile of light emitted from grating region 120 can be designed to substantially match the cross-sectional mode profile of a single-mode optical fiber in the x-y dimension.

Fig. 1B shows an example of an optical coupler 101 that may be implemented in a photonic integrated circuit 100. The optocoupler 101 can also be implemented in any of any other photonic integrated circuits described in this application, or in another photonic integrated circuit not described in this application.

Optical coupler 101 includes an interference region 110 and a grating region 120. Grating region 120 includes grating valleys 118 and grating peaks 126 that together form a grating having a grating length L_GratingThe grating of (2). The height difference between grating peaks 128 and grating valleys 18 determines the grating height. The ratio of the grating width to the sum of the peak width and the valley width of the grating along the wave propagation direction determines the duty cycle of the grating. The sum of the grating peak width and the grating valley width determines the period of the grating. By adjusting the grating height, duty cycle, grating period, grating shape, cladding covering the grating, or combinations thereof, the directionality and far field angle of light emitted/received by grating region 120 can be determined. For example, the grating height and duty cycle may be modified to optimize the directionality of the light. As another example, the grating period and duty cycle may be adjusted to achieve a desired far-field angle that may be best suited for the target application.

In some embodiments, the height of the grating peaks may be higher than the height of the first reflective region 106 and/or the second reflective region 114. For example, grating region 120 can be formed by planarizing first reflective region 108, interference region 110, and second reflective region 114 by polishing, and then depositing another layer of material on the planarized surface, such that grating region 120 can be formed by patterning and etching.

In some other embodiments, the height of the grating valleys may be lower than the height of the first reflective region 106 and/or the second reflective region 114. Fig. 1C shows an example of an optical coupler 103 in which the height of the grating valleys 119 is lower than the height of the first and second reflective regions 106, 114. For example, first reflective region 106, interference region 110, and second reflective region 14 can be planarized by polishing, and then grating region 120 can be formed on the polished surface by patterning and etching interference region 110. The optical coupler 103 may be implemented in the photonic integrated circuit 100. The optical coupler 103 may also be implemented in any other photonic integrated circuit described in this application, or in another photonic integrated circuit not described in this application.

Fig. 1D shows an example of an optical coupler 105 that includes waveguide region 102, interference region 110, grating region 120, and second reflective region 114, but does not include first reflective region 106. The boundary 130 between the waveguide region 102 and the interference region 110 is represented by a dashed line 130 because, in some embodiments, the waveguide region 102 and the interference region 110 are composed of the same material or have substantially equal effective indices of refraction.

In the case where the light in the interference region 110 attenuates below the threshold value after propagating in the interference region 110 for one cycle, the optical coupler 105 does not include the first reflection region 106. For example, a standing wave may be generated in the interference region 110 by interference between forward light incident on the second reflection region 114 and backward light reflected by the second reflection region 114. The standing wave may be reduced near the boundary 130 between the waveguide region 102 and the interference region because the light reflected by the second reflective region 14 is attenuated below a threshold beyond the boundary 130. The threshold value may be, for example, less than 10% of the initial incident optical power. By substantially matching the grating pattern in grating area 120 with the interference pattern in interference area 110, optical coupler 105 can be used to redirect light propagating along a first direction to a second direction different from the first direction without first reflective area 106. For example, the optical coupler 105 may be used to direct light into a second direction that is substantially perpendicular to the first direction. In some embodiments, without first reflective region 106, the optical coupler can still efficiently redirect incident light if the light is attenuated below a threshold after propagating a single cycle in interference region 110. In some embodiments, grating region 120 needs to provide sufficient single-cycle attenuation in order to maintain high efficiency without the introduction of first reflective region 106. E.g. grating length L_GratingLong enough to provide sufficient single-cycle attenuation before reaching the boundary 130.

Fig. 2 is an example of a grating pattern 207 that substantially matches a standing wave pattern 205 within an interference region. The description of fig. 2 may be applied to any of the optical couplers described in this application. In general, the round-trip phase shift is the sum of the phase shift introduced by the single-cycle propagation and the phase shift introduced by the reflector. For simplicity of description, it may be assumed that the phase shift introduced by the reflector is zero, so that the resonance condition "round-trip phase shift equal to 2m π" may be considered the same as "single-cycle phase shift equal to 2m π", where m is any integer.

In some embodiments, light propagating in a waveguide may be limited in two dimensions. For example, referring to fig. 1A, light propagating in waveguide region 102 is confined in the y and z dimensions. When light enters the interference region, the confinement of the waveguide may be weakened and the light propagates like a point wave within the interference region. For example, the interference zone 110 may be designed to confine light tightly in the z-dimension and loosely in the y-dimension. The point wave reaches the reflector 211, is reflected, and may form a standing wave intensity pattern 205 in the interference region by interference of the forward propagating wave 201 and the backward propagating wave 203.

In some embodiments, grating pattern 207 may be designed to substantially match standing wave pattern 205. By matching the standing wave pattern 205, the grating pattern 207 can act as an optical antenna and be the most efficient way for light to leave the interference region. Each period of the grating structure may be used to emit light as a point wave, and all point wave fronts emitted from the respective grating periods are combined into a planar wavefront, which propagates in the vertical direction with low loss. For example, one theoretical condition for ideal matching may be d2 ═ 2 × d 1. In some embodiments, there may be two gratings, where their individual periodicity (pattern) substantially matches the standing wave periodicity (pattern), i.e., d2 through-2 x d1, such that the two gratings have similar periodicities. Furthermore, the two gratings may differ in, for example, grating peak and/or valley width (duty cycle), and be shifted by a distance corresponding to a pi phase shift,

based on the material quality and physical dimensions of the interference region and the grating structure, the single-cycle attenuation coefficient α and the corresponding phase shift of the resonance condition within the interference region can be calculated. For example, the interference region may be composed of a material having a specific absorption coefficient for the guided light, which contributes to the single-cycle attenuation coefficient. As another example, light may be emitted by the grating region during propagation, which also contributes to the single-cycle attenuation coefficient. Typically, after a single cycle of propagation in the interference region (i.e., forward propagation from boundary 213 to reflector 211, and then backward propagation from reflector 211 to boundary 213), light is attenuated based on a single cycle attenuation coefficient. The term "single-cycle attenuation coefficient α" as used in this application refers to the ratio between the residual optical power after single-cycle attenuation and the initial optical power.

In some embodiments, to substantially reduce back reflection losses, a reflective region (e.g., first reflective region 108) may be placed at boundary 213, wherein the reflectivity of the reflective region at boundary 213 is configured to substantially match the single-cycle attenuation coefficient α. By substantially matching the reflectivity of the reflective region at the boundary 213 to α, light reflected from the boundary 213 back to the incident light source (at the left side of 213) (from the left hand side of 213) and transmitted through the boundary 213 back to the incident light (at the left hand side of 213) (from the right hand side of 213) cancel each other out after multiple passes due to destructive interference, which means that almost all of the power of the original incident light (incident to the region between 213 and 211 from the left side of 213) is transferred to the region between 213 and 211. In some embodiments, the single-cycle attenuation coefficient α may be close to zero. In this case, the respective reflectivity r at the boundary 213 may be set to zero, which corresponds to the optical coupler 105 in fig. 1D, wherein the first reflective region 106 is not comprised in the optical coupler 105. In some embodiments, the reflectivity r at the boundary 213 may be set as high as the reflectivity of the reflector 211 (e.g., close to 1) to form a highly confined cavity along the x-direction, where light may enter or exit the cavity through another direction (e.g., in the z-direction).

In some embodiments, there may be non-ideal factors that affect performance. For example, the change in effective index may occur from etching the grating region over the interference region. As another example, the etching process may not produce a straight line from grating peak to grating valley. Although the theoretical matching condition is d 2-2 d1, slight deviations from the exact condition can be expected during practical implementation. Such deviations do not change the function of the optocoupler, but affect the efficiency. However, any reasonable deviation from the ideal is within the scope of the present disclosure, where efficiency is acceptable for the target application. An iterative process of manufacturing an optical coupler, testing the optical coupler, and then redesigning the optical coupler can ameliorate this problem.

Fig. 3A shows an example of a view of the raster pattern 331 on a plane along the x-y dimension. The description of fig. 3A may be applied to any of the optical couplers described in this application. The grating pattern 331 comprises an array of one-dimensional grating structures 301a-n and 303a-n along the x-direction, where n is any integer greater than 1. In some embodiments, grating structures 301a-n and 303a-n may be composed of different materials. For example, grating structures 301a-n may be composed of silicon, while grating structures 303a-n may be composed of InP. As another example, grating structures 303a-n may include a metal layer that forms a surface plasmon effect that couples light from an external medium to an interference region. The arrangement of 301a,303a,301b,303b, ·,301n and 303n forms a grating in the grating region.

Fig. 3B shows an example of a view of the raster pattern 332 in a plane along the x-y dimension. The description of fig. 3B may be applied to any of the optical couplers described in this application. The grating pattern 332 comprises an array of one-dimensional grating structures 305a-n along the x-direction, where n is any integer greater than 1. In some embodiments, grating structures 305a-n may be grating peaks of a grating. In some other embodiments, grating structures 305a-n may be grating valleys of a grating. 305a,305b and 305n form a grating in the grating region.

Fig. 3C shows an example of a view of the raster pattern 333 in a plane along the x-y dimension. The description of fig. 3C may be applied to any of the optical couplers described in this application. The grating pattern 333 includes a two-dimensional rectangular grating structure 307a to 307n along the x-direction, and an array of 307a to 307k along the y-direction, in some embodiments the rectangular grating structure 307a may be a grating peak of a grating, in some other embodiments the rectangular grating structure 307a may be a grating valley of a grating. In some embodiments, the rectangular grating structure 307a may be composed of the same material as the layer 308, such as silicon. In some embodiments, the rectangular grating structure 307a may be composed of a different material than the layer 308. For example, the rectangular grating structure 307a may be composed of silicon, while the layer 308 may be composed of InP. In some embodiments, the rectangular grating structure 307a may be square or non-square, or a combination of both structures. The arrangement of rectangular grating structures 307a-n and 307a-k in the x-y plane forms a grating in the grating region. In some embodiments, the period of the grating along x-direction 321 and the period of the grating along y-direction 322 substantially match the periods of the interference pattern in layer 308 along the x-and y-directions, respectively.

Fig. 3D shows an example of a view of the raster pattern 334 on a plane along the x-y dimension. The description of fig. 3D may be applied to any of the optical couplers described in this application. The grating pattern 334 includes an array of two-dimensional arbitrarily shaped grating structures 309a to 309n, where n is any integer greater than 1. In some embodiments, the arbitrary shaped grating structure 309a may be a grating peak of a grating. In some other embodiments, the arbitrary shaped grating structure 309a may be a grating valley of a grating. In some embodiments, the arbitrary shaped grating structure 309a may be composed of a different material than layer 310. For example, the grating structure 309a of arbitrary shape may be composed of silicon dioxide, while the layer 308 may be composed of silicon. In some embodiments, the arbitrary shaped grating structure 309a may be triangular or elliptical or a combination of different shapes. The arrangement of the arbitrarily shaped grating structures 309a-n in the x-y plane forms a grating in the grating region.

Fig. 3E shows an example of a view of the raster pattern 335 in a plane along the x-y dimension.

The description of fig. 3E may be applied to any of the optical couplers described in this application. The grating pattern 335 includes an array of two-dimensional arbitrarily shaped grating structures 313a to 313n, where n is any integer greater than 1. In some embodiments, numerical analysis may be used to determine the shape of any of the arbitrarily shaped grating structures 313a to 313 n. For example, the shape of each arbitrary shape structure 313a to 313n may be designed using a Finite Difference Time Domain (FDTD) analysis program to optimize the coupling efficiency. In some implementations, numerical analysis may be used to determine the distance between each of the arbitrarily shaped grating structures 313a to 313 n. For example, a Finite Difference Time Domain (FDTD) analysis procedure may be used to determine the distance between each of the arbitrary-shaped structures 313a to 313n to optimize the coupling efficiency. The arrangement of the arbitrarily shaped grating structures 313a-n in the x-y plane forms a grating in the grating region.

In some embodiments, the one-dimensional grating shown in fig. 3A and 3B may have a one-dimensional lattice vector (which defines the cell grid size) designed such that the position of the in-phase antinodes of the interfering waves substantially match the position of the grating valleys and/or peaks.

In some embodiments, the two-dimensional gratings shown in fig. 3C, 3D, and 3E may have a two-dimensional lattice vector (which defines the cell grid size and shape) designed such that the position of the in-phase antinodes of the interference region substantially matches the position of the grating valleys and/or peaks.

Fig. 4A illustrates an exemplary photonic integrated circuit 400 having a grating-based optical coupler formed over a light source. Photonic integrated circuit 400 includes a light source region 430 configured to generate incident light. In some embodiments, the light source region 430 may generate incoherent light. For example, a III-V quantum well or quantum wire or quantum dot laser diode may include one or more layers of active material that produce incoherent light when pumped by electrical carriers. In some embodiments, incoherent light may be coupled into interference region 410 by spontaneous emission. In some embodiments, source region 430 may be confined at a surface other than the surface coupled to interference region 410.

The optical coupler includes a first reflective region 406, a second reflective region 414, an interference region 410, and a grating region 420. The structures of the first reflective region 406, the second reflective region 414, the interference region 410, the grating region 420, and the grating 418 can be implemented by any of the corresponding structures described herein, e.g., the corresponding structures in fig. 1A-3E. For example, a grating may be implemented as shown in FIG. 3A, comprising two gratings 301a-n and 303A-n, wherein their respective periods match the interference period (pattern), but with different duty cycles. As another example, the grating may be implemented as shown in fig. 3C, wherein a two-dimensional rectangular grating structure is formed. In some embodiments, the interference region 410 and the grating region 420 are composed of silicon or a III-V semiconductor, the light source region is composed of a III-V semiconductor, and the first and second reflective regions 406 and 414 include a metal coating or Bragg reflector, such as a DBR and/or DFB (distributed feedback) structure, with a Bragg period equal to half the wavelength.

The first and second reflective regions 406, 414 are configured to reflect incident light in a direction opposite to the direction of propagation of the incident light, as indicated by arrow 434. The interference region 410 is formed between the first and second reflection regions 410 and 414 and is coupled to the light source region 430. The interference zone 410 may be configured to (i) direct light generated by the light source zone 430 to propagate in a first direction (the x-direction in fig. 4A), and (ii) limit interference light formed by light reflected between the first and second reflective zones 406, 414.

A portion of the light generated in light source region 430 may be coupled to interference region 410 by spontaneous emission or any other suitable coupling mechanism. Light coupled into the interference zone 410 may resonate in the x-direction as indicated by arrow 434. Similar to the operation described in FIG. 1A, the first and second reflective regions 406, 414 provide reflective surfaces that form cavities in the interference region 410, where standing wave patterns can be formed. Since the interference zone 410 has a fixed cavity length L_CavityThe standing wave can therefore only resonate at certain wavelengths, and the interference region 410 can therefore act as a wavelength filter.

Grating zone 420 includes a grating 418 formed over an area that confines at least a portion of the interfering light. The grating 418 is configured to emit a portion of light in a z-direction substantially perpendicular to the x-direction. In some embodiments, a grating 418 may be designed and fabricated in the grating region 420 to substantially match the standing wave pattern in the interference region 410. By matching the standing wave pattern, the grating 418 can act as an optical antenna and be the most efficient way for light to exit the interference region 410. Each grating period may be used to emit light as a point wave, and all point wave fronts emitted from the respective grating periods are combined into a planar wavefront, which propagates in the z-direction with low loss.

FIG. 4B shows an exemplary photonic integrated circuit 401 having a grating-based optical coupler where an optical source region 431 is coupled to an interference region 411 by being embedded in the interference region 411. The structures of the first reflective region 416, the second reflective region, the interference region 411, and the grating region 421 may be implemented by any corresponding structures described in this application, for example, the corresponding structures in fig. 1A-3E. The light source region includes layers of active material, such as alternating layers of gallium arsenide (GaAs) and aluminum gallium arsenide (AlGAAs) or alternating layers of InGaAs and InP. Any other combination of active material layers forming quantum dots, lines and well structures that produce incoherent or coherent light is also within the scope of the present invention.

The interference zone 411 is formed between the first reflective zone 416 and the second reflective zone 424. The first and second reflective regions 416, 424 may be formed, for example, by a metal coating or a bragg reflector, such as a DBR and/or DFB structure having a bragg period equal to half the wavelength.

In contrast to the description of FIG. 4A, where light is generated outside of interference zone 410, but in FIG. 4B, light is generated inside of interference zone 411. The generated light resonates in the interference region 411 in the x direction between the first reflection region 416 and the second reflection region 424 to generate coherent light and form a standing wave pattern. The grating region 421 can be designed to substantially match the standing wave pattern, wherein coherent light is emitted from the photonic integrated circuit 401 through the grating region 421 in the z-direction. For example, a grating may be implemented as shown in FIG. 3A, comprising two gratings 301a-n and 303A-n, with their respective periods matching the interference pattern but with different duty cycles. As another example, the grating may be implemented as shown in fig. 3C, wherein a two-dimensional rectangular grating structure is formed. In some embodiments, the substrate 440 may be used as a support layer. In some embodiments, the substrate 440 may include an absorbing layer to further reduce light propagating in the-z direction.

Fig. 4C shows an exemplary photonic integrated circuit 402 with a grating-based laser device in which the grating regions are formed on two reflective regions. When a DBR or DFB structure is applied to two reflectors, the standing wave in the interference region can penetrate into two reflective regions forming two evanescent portions of the standing wave. In some embodiments, the two evanescent portions of the standing wave pattern substantially match the grating pattern. In some embodiments, the light source region is coupled to the interference region, and in some embodiments, the light source region is coupled to the interference region by being at least partially embedded in the interference region. In some embodiments, between the interference region and the grating region or between the grating region and the reflective region, there may be further included tapered waveguide distributed feedback or distributed bragg reflector (DFB or DBR) regions, where their period and duty cycle or both may be slightly modified to form a smooth effective index transition from the interference region to the grating region or from the grating region to the reflective region. In some embodiments, the tapered region has the same period as the DFB or DBR reflective region, but its duty cycle gradually increases or decreases in the direction from the interference region to the reflective region. The description of the tapered region with gradually increasing or decreasing period/duty cycle may be applied to any of the optocouplers described in this application.

Fig. 4D shows an exemplary photonic integrated circuit 404 having a grating-based laser device in which a grating region is formed on one of the reflective regions. When a DBR or DFB structure is applied to a reflector, the standing wave in the interference region can penetrate into a reflective region that forms the evanescent portion of the standing wave. In some embodiments, the evanescent portion of the standing wave pattern substantially matches the grating pattern. In some embodiments, the light source region is coupled to the interference region. In some embodiments, the light source region is embedded in the interference region.

FIG. 4E shows an exemplary photonic integrated circuit 403 having a grating-based optical coupler integrated with a light source, where the interfering light is controlled by a p-n junction. Photonic integrated circuit 403 includes light source region 441, p-doped region 442, interference region 443, n-doped region 444, grating region 445, first reflective region 446, and second reflective region 448. The structures of light source region 441, p-doped region 442, interference region 443, n-doped region 444, grating region 445, first reflective region 446, and second reflective region 448 may be implemented by any corresponding structures described herein, e.g., the corresponding structures in fig. 1A-3E.

Similar to the description of FIG. 4A, incoherent light is generated in light source region 441 with a portion of the light coupled into interference region 443. The coupled light resonates in the interference region 446, between the first and second reflective regions 446, 448 along the x-direction to form a standing wave pattern and produce coherent light. The grating in the grating area 445Designed to substantially match the standing wave pattern, and coherent light can be at + z or

In the direction, it emerges from photonic integrated circuit 403 through grating 443, depending on the design of grating 445.

In some embodiments, the n-doped region 444 and the p-doped region 442 can be configured to provide an electric field in the interference region 443 by applying a voltage or current across the n-doped region 444 and the p-doped region 442. The interference region 443 may be configured to provide different interference patterns by applying a voltage or current across the n-doped region 444 and the p-doped region 442 due to the generation, recombination, injection, or depletion of free carriers. In the case where the interference pattern is changed due to a change in refractive index, the interference region 443 may stop lasing or may support another lasing wavelength. Thus, applying a voltage or current across the n-doped region 444 and the p-doped region 442 may serve as a tunable wavelength lasing mechanism or modulation of coherent light.

At this time, incoherent light is generated in light source region 441, wherein a portion of the light is coupled to interference region 443. For example, light source region 441 may include indium gallium arsenide (InGaAs) quantum wells or quantum wire or quantum dot structures. The coupled light resonates between the first and second reflection regions 446 and 448 in the interference region 443 to generate coherent light and form a standing wave pattern. The grating in the grating region 445 is designed to substantially match the standing wave pattern, and coherent light is emitted from the interference region 443 through the grating region 445 in a direction substantially perpendicular to the resonant direction of the interfering light. In some embodiments, the tapered region may be used in an interference region or a reflection region, where the narrower portion of the tapered region is used to suppress higher order modes, while the wider portion of the tapered region, e.g., grating region 445, may be used to match out-coupling devices with different beam shape, area, and numerical aperture requirements. The description of the taper region width may be applied to any of the optical couplers described in this application. In some embodiments, a reflective region (e.g., DBR structure, metal coating, etc.) may be used on top of or below the interference region 443 to modify the directivity to another direction.

Fig. 4F shows an exemplary photonic integrated circuit 407 having a light source region 462 coupled to a grating-based optical coupler by a grating region 466. The photonic integrated circuit 407 includes a light source region 462, a first reflective region 478, a second reflective region 476, an interference region 472, a boundary 474, and a grating region 466. The structures of the source region 462, the first reflective region 478, the second reflective region 476, the interference region 472, and the grating region 466 can be implemented by any corresponding structures described herein, for example, the corresponding structures in fig. 1A-3E. For example, a grating may be implemented as shown in FIG. 3A, comprising two gratings 301a-n and 303A-n, where their respective periods match the interference pattern but have different duty cycles. As another example, the grating may be implemented as shown in fig. 3C, wherein a two-dimensional rectangular grating structure is formed. As another example, the first and second reflective regions 478 and 476 may be formed, for example, by a metal coating or a bragg reflector such as a DBR and/or DFB structure having a bragg period equal to half the wavelength.

At this point, incoherent light is generated in the source region 462 and coupled into the interference region 472 by spontaneous emission or another suitable coupling mechanism. The coupled incoherent light is reflected by reflective regions 476 and 478 and resonates in the x-direction. When coherent light reaches the lasing threshold, it may be emitted in the + z or-z direction, depending on the design of the grating region 466. In some embodiments, the grating region 466 can be designed to direct a substantial portion of the light into the-z direction so that the emitted light is not coupled back into the source region 462.

In some embodiments, reflector 478 may be a partial reflector having less reflectivity than reflector 476. Incoherent light generated in the source region 462 may couple to the interference region 472 by spontaneous emission and resonate along direction 470. When the lasing threshold is reached, coherent light may propagate in the-x direction through boundary 474 into partial reflector 478 and then into the waveguide while at + z or

In the direction to an external medium for further processing.

Fig. 4G shows an exemplary photonic integrated circuit 405 illustrating a grating-based laser device with two grating structures having similar periods in the interference region. The two grating structures a and B in fig. 4G may correspond to 301a-n and 303A-n in fig. 3A, wherein grating a and grating B may be distinguished by, for example, two different grating peak widths. Two grating structures are formed on the interference region, which can be interpreted as being bounded by the reflectors 1 and 2. The two grating structures redirect coherent light propagating and resonating in the lateral direction to the up or down vertical direction by adjusting the grating parameters (e.g., grating height, duty cycle, refractive index of the layer material) of the two grating structures to achieve the desired directionality. In some embodiments, the effective refractive index of the region above the two grating structures is less than the effective refractive index of the two grating structures. In some embodiments, the effective refractive index of the interference region is less than the effective refractive indices of the two grating structures. In some embodiments, the two grating structures a and B each have a duty cycle of less than 50%. Electrical contacts of the laser device from the upper or lower surface can be produced. In some embodiments, electrical contacts of the laser device may be realized from the upper surface and the emitted light may be redirected in a downward direction so that the laser device may be flip chip bonded to a substrate to achieve high speed electrical contact performance without blocking the vertically emitted light.

Fig. 4H shows an exemplary photonic integrated circuit 415 that exhibits a grating-based laser device with two grating structures with similar period and quarter-wave phase shift in the interference region. Compared to the laser apparatus shown in fig. 4G, which supports two lasing modes, the quarter-wave phase shift introduced in the interference region breaks the symmetry by removing one section from the grating structure, so that the laser apparatus shown in fig. 4H can support only one lasing mode. In some embodiments as shown, electrical contacts of the laser device may be realized from the upper surface and the emitted light may be redirected in a downward direction so that the laser device may be flip chip bonded to the substrate to achieve high speed electrical contact performance without blocking the vertically emitted light.

Another way of explaining the laser device in fig. 4H based on the concept of fig. 4C is shown in fig. 4I. Two grating regions 411 and 413 separated by a quarter wave phase shift are formed, where each grating region partially overlaps with reflective regions 417 and 419. The two grating reflector overlap regions redirect coherent light propagating and resonating in the lateral direction to the vertical direction and support only one lasing mode. In some embodiments, electrical contacts of the laser device may be realized from the upper surface and the emitted light may be redirected in a downward direction so that the laser device may be a flip chip bonded to a substrate to achieve high speed electrical contact performance without blocking the vertically emitted light.

Fig. 4J shows an embodiment in which the grating-based laser device 423 is a flip chip bonded to the substrate 421 and light is emitted from the back side of the laser device. In some embodiments, the back side of the grating-based laser device 423 from which light is emitted may be further recessed to facilitate light emission.

Fig. 4K shows an exemplary photonic integrated circuit 431 demonstrating a grating-based laser device with two grating structures with similar period and quarter-wave phase shift in the interference region. In contrast to the laser device shown in fig. 4H, fig. 4K further illustrates a period/duty cycle taper 433 between the quarter-wavelength phase-shifting interference region and the grating region. In some embodiments, the tapered region 433 has a period, d1, that is similar to or less than the period of the DFB reflective region 435, but its duty cycle gradually increases in the direction from the center to the reflective region, as shown in fig. 4K. In some embodiments, the same concept of the periodic/duty cycle tapered region can be implemented between the grating region and the reflective region.

Fig. 4L shows an exemplary photonic integrated circuit 451, which exhibits a grating-based laser device with two grating structures with similar period and quarter-wave phase shift in the interference region. In contrast to fig. 4K, in fig. 4L the quarter-wave phase shift introduced in the interference region breaks the symmetry by adding a section to the grating structure. In some embodiments, the tapered region 453 has a period, d1, that is similar to or greater than the period of the DFB reflective region, but its duty cycle gradually decreases in the direction from the center to the reflective region, as shown in fig. 4L.

For conventional laser diodes, the basic functional principle is by providing electrical carriers from two terminals (P and N) or electrodes into a light source region comprising at least one Photon Emitting Material (PEM), such as a III-V semiconductor to be used as a gain material. The terminals are typically forward biased so that the electrons and holes meet in the PEM, recombine and emit photons. As previously shown in fig. 1A, the first reflector 106 and the second reflector 114 define a resonant structure (i.e., an interference zone or cavity 110) that extends along a lateral direction while redirecting light out along a vertical direction 123. When the interference region 110 comprises a PEM layer and two terminals are provided so that photons can be generated in the interference region 110, these photons can resonate in the lateral direction between the two reflectors 106 and 114. In the present disclosure, a third type of terminal (conventionally two terminals may be considered as "conductive terminals") is included to serve as a gate terminal to attract/suppress/inject/recover certain types of carriers towards the gate region, thereby modulating the amount of carriers to be recombined. The electrical contact to the terminal can be of various forms such as a direct metal contact (e.g., MESFET type), a junction (e.g., JFET type), or through a dielectric for field control (MOSFET type). Although there are many possible implementations for this control terminal, the core concept is to provide a second set of electric fields to change the amount of carriers that recombine in addition to the first set of electric fields used to inject carriers to generate photons. This "gate control" scheme can have a larger modulation bandwidth than conventional laser diode direct modulation. Advanced modulation schemes can also be implemented using application of voltages to gate levels to encode more than one bit of data (on/off) to obtain different output light power levels. This type of modulation is similar to amplitude modulation where different voltage levels are applied to the gate. Various exemplary embodiments for implementing the gate controllable laterally resonant optical emitter structure are described in more detail in the following paragraphs.

Fig. 5A shows a cross-sectional view of an exemplary optical device 561 for emitting light. The optical arrangement 561 for emitting light comprises a light source region 570 comprising a layer 572 of Photon Emitting Material (PEM). Further, the light source region 570 may be an interference region defined by two reflectors. Optical device 561 further includes a first electrode 591 coupled to light source zone 570, a second electrode 592 coupled to light source zone 570, and a third electrode 593 coupled to light source zone 570. As shown in the figure, the first electrode 591 includes a conductive layer 591a and a doped region 591 b. The conductive layer 591a is, for example, a metal layer, and the doped region 591b is, for example, an n-type doped region. Similarly, the second electrode 592 includes a conductive layer 592a and a doped region 592 b. Conductive layer 592a is, for example, a metal layer, and doped region 592b is, for example, a p-type doped region. That is, the first electrode 591 and the second electrode 592 have different polarities so that carriers (electrons and holes) may be injected into the light source region 570. For example, electrons are injected into the PEM layer 572 through the n-type doped region 591b, while holes are injected into the PEM layer 572 through the p-type doped region 592b, such that the electrons and holes combine in the PEM 572 to generate photons. The third electrode 593 includes a conductive layer 593a and an insulating layer 593b, wherein the insulating layer 593b is located between the conductive layer 593a and the light source region 570. In some embodiments, the conductive layer 593a comprises doped polysilicon or metal, while the insulating layer 593b comprises oxide or nitride or semi-insulating III-V semiconductor. As shown in the figure, a voltage V1 is applied to the first electrode 591, a voltage V2 is applied to the second electrode 592, and a third voltage V3 is applied to the third electrode 593, wherein V2> V1. In some embodiments, the electrode with the lowest voltage may be used as ground. In some embodiments, the third electrode 593 attracts electrons (shown by the dashed line) and reduces the amount of electrons to recombine with holes from the second electrode 592 if V3> V2. In some embodiments, if V2> V3> V1, the third electrode 593 attracts both holes from the second electrode 592 and electrons from the first electrode 591. In some embodiments, the third electrode 593 attracts holes from the second electrode 592 if V3< V1. In some embodiments, the third electrode 593 may be P-type if it is intended that V3 be greater than V2, and the third electrode 593 may be N-type if it is intended that V3 be less than V1.

Note that other similar configurations of the third electrode besides the conventional two conductive electrodes are possible and should be included in the present disclosure as long as the key concept is followed. Some further examples are shown in the block diagrams included in fig. 5B-5G. In general, an optical device for emitting light according to an embodiment includes: a third electrode for modulating the amount of electrical carriers for recombination; and a transverse optical cavity structure for optical resonance, as shown by the previous examples.

Fig. 5B-5E show block diagrams of optical devices for light emission with a lateral cavity. In these examples, V1 and V2 are used as voltages applied to the "conducting" electrodes (i.e., first electrode 591 and second electrode 592) of the laser, and V3 is used as a voltage applied to the "modulating" electrodes (i.e., third electrode) to control the amount of carriers recombined to emit photons. For more general purposes, the P or N type is omitted from the description. The solid line with two arrows indicates the region where recombination occurs and is typically inside a III-V semiconductor, a III-V semiconductor-based quantum well structure, a III-V semiconductor-based quantum wire structure, a III-V semiconductor-based quantum dot structure, or other material with a direct bandgap. As shown in fig. 5B, first and second electrodes 591 and 592 are located on two opposite sides of interference region 570. The Photon Emitting Material (PEM) is omitted from the description herein and may be considered as partially embedded within the interference region 570. The third electrode 593 is positioned between the first and second electrodes 591 and 592 to modulate carriers between the first electrode 591 and the second electrode 592. Fig. 5C shows another embodiment, in which a third electrode 593 is located outside a connection path of the first and second electrodes 591 and 592. In this case, the third electrode 593 can still perform a modulation function by extracting carriers from the carrier recombination region. In the examples shown in fig. 5B and 5C, the electrodes are at similar levels. In the examples shown in fig. 5D and 5E, at least one electrode is located on a different layer than the other electrodes. Similar to the example shown in fig. 5A, the first electrode 591 includes a conductive layer and a doped region. That is, the first electrode 591 and the second electrode 592 have different polarities so that carriers (electrons and holes) may be injected into the light source region. The third electrode 593 includes a conductive layer and an insulating layer, wherein the insulating layer is located between the conductive layer and the interference region 570. Further, in the examples shown in fig. 5B to 5E, light reflectors (not shown) are provided on two opposite faces of the interference area 570, and correspond to the arrow directions of the solid line areas in fig. 5D. Upon application of a current or voltage between the first and second electrodes 591 and 592, photons may be generated and resonate along a solid line region, and are defined by the light reflector in fig. 5D. A voltage or current may be applied to the third electrode 593 to attract or repel carriers (shown by the dotted line) and thus change the amount of electrons or holes to recombine in the interference region, thereby implementing a modulation function. In contrast to fig. 5D, fig. 5E shows another embodiment by switching the position of one conducting electrode and one modulating electrode. The injection path (solid line) and modulation path (dashed line) are changed accordingly.

Fig. 5F-5K show block diagrams of optical devices for emitting light with several other embodiments of electrode orientations similar to the numbering and notation used in fig. 5A-5E. Fig. 5F shows an embodiment with vertically oriented conductive electrodes 591 and 592 and sidewall modulating electrodes 593. FIG. 5G shows the sidewall conductive electrodes 591 and 592 and the upper modulating electrode 593. FIG. 5H shows an embodiment similar to FIG. 5F, but with more than one modulating electrode 593.

Fig. 5I shows two conductive paths (solid lines) and a bottom vertical modulation electrode 593. Fig. 5J shows two conductive paths (solid lines) and a bottom vertical modulation electrode 593. Fig. 5J shows two conductive paths (solid lines) and a modulating electrode 593 of the sidewall.

Since all of the primary elements shown in the examples are combined to form other designs or embodiments, such as the relative orientation of the quantum wells or quantum wire or quantum dot structures of the PEM to the cavity (e.g., parallel or perpendicular to the resonance region), a grating form, the use of two conventional conductive electrodes, or the inclusion of additional modulating electrodes, the figures shown herein are only a few of the many possible embodiments of the present disclosure. Thus, any design/structure that follows the concepts of the present disclosure should still be considered within the scope of the present disclosure. Furthermore, the different electrodes and contacts may be located at different layers in the lateral or vertical direction. It is noted that for simplicity of viewing, the drawings shown as design examples are not drawn to scale. Further, the interference region (cavity) may comprise a PEM such as GaAs, InGaAs, InGaAsP, InGaAsN, InAs, silicon nanofibers, germanium nanocrystals, or other materials, so long as the PEM layer may be added over or at least partially embedded in the interference region by bonding or material growth. Furthermore, more than one cavity may be cascaded in the direction of resonance for a wider operating bandwidth. Accordingly, any embodiments that follow the concepts set forth in the claims should be considered within the scope of the present disclosure.

Fig. 6A shows a cross-sectional view of an exemplary grating-based laser device (hereinafter laser device) 661 with front-side modulation, where front-side modulation refers to the modulation gate being on the side that emits light. Laser device 661 includes layers of active material such as alternating layers of gallium arsenide (GaAs) and aluminum gallium arsenide (AIGaAs) or alternating layers of InGaAs and InP as Photon Emitting Material (PEM)672, which are optically coupled to interference region 670. Any other combination of active material layers forming quantum dots, lines, and well structures that produce incoherent or coherent light is also within the scope of the present disclosure. The laser apparatus 661 includes an interference zone (cavity) 670 defined by a first reflector 666 and a second reflector 674. In the example shown, lasing device 661 further includes a grating region 680 formed in an upper portion of interference region 670. The laser device 661 further includes a first contact 691, a second contact 692, and a third contact 693, wherein the first contact 691 and the second contact 692 are located at opposite ends of the interference region 670, and the third contact 693 is located above the interference region 670 and between the first contact 691 and the second contact 692. The first electrode 691 includes a conductive layer 691a and a doped region 691 b. The conductive layer 691a is, for example, a metal layer, and the doped region 691b is, for example, an n-type doped region. Similarly, the second electrode 692 includes a conductive layer 692a and a doped region 692 b. The conductive layer 692a is, for example, a metal layer, and the doped region 692b is, for example, a p-type doped region. That is, the first electrode 691 and the second electrode 692 may have different polarities so that carriers (electrons and holes) may be injected into the interference region 670 and recombine in the PEM 672. For example, electrons are injected through the n-type doped region 691b and holes are injected through the p-type doped region 692b, so that the electrons and holes recombine to generate photons. The third electrode 693 includes a conductive layer 693a and an insulating layer 693b, wherein the insulating layer 693b is formed between the conductive layer 693a and the light source region 670. In addition, the conductive layer 693a comprises doped polysilicon or metal and the insulating layer 693b comprises oxide or nitride or other semi-insulating III-V semiconductor, and in some embodiments, the interference region comprises a conductive material such that carriers injected from the contact can be transferred into the PEM region to recombine to generate photons.

Using an N-type as the first contact (electrode) 691 and a P-type as the second contact 692, when voltages V1 and V2(V2> V1) are applied to the first contact 691 and the second contact 692, respectively, electrons will be injected at the N-type contact 691, and holes will be injected at the P-type contact 692. Thus, when an electron recombines with a hole, a photon is generated at the active material layer 672. If the voltage V3 applied to the third contact 693 is greater than V2, the third contact 693 will attract electrons (as shown by the dashed line) and reduce the amount of electrons that recombine with holes from the P-type contact 692. If V2> V3> V1, third contact 693 will attract electrons and holes from N-type contact 691 and P-type contact 692, respectively. If V3< V1, the third contact 693 will attract holes from the P-type contact 692. In this way, the third contact 693 is used for carrier modulation of the laser device 661. The third contact 693 may be separated from the interference zone 670 by a medium 694 to adjust the electric field penetrating into the interference zone. The medium 694 may be omitted if a direct carrier modulation mechanism such as PN (junction) or MS (direct metal contact) modulation is applied. In the laser device 661 shown in fig. 6A, carriers (electrons or holes) are injected into the PEM region 672 that are optically and electrically coupled to the interference region 670 when appropriate voltages are applied to the first contact 691 and the second contact 692, respectively.

The structures of the first reflector 666, the second reflector 674, the interference region 670, and the grating region 680 may be implemented by any corresponding structures described herein, e.g., the corresponding structures in fig. 1A-3E. For example, a grating may be implemented as shown in FIG. 3A, comprising two gratings 301a-n and 303A-n, with their respective periods matching the interference period but having different duty cycles. As another example, the grating may be implemented as shown in fig. 3C, wherein a two-dimensional rectangular grating structure is formed. As another example, the first and second reflective regions 666 and 674 may be formed, for example, with a metal coating or a bragg reflector, such as a DBR and/or DFB structure having a bragg period equal to half the wavelength. In some embodiments, the interference region 670 is comprised of a III-V semiconductor and at least one of the first and second reflectors 666 and 674 includes an angled mirror, a DBR mirror, a waveguide ring mirror, or a metal layer. The generated light resonates in the interference region 670 in a direction between the first reflector 666 and the second reflector 674 to generate coherent light and form a standing wave pattern. Grating region 680 may be designed to substantially match a standing wave pattern in which coherent light is emitted from laser device 661 through grating region 680 in a direction different from the resonant direction. In some embodiments, the grating is formed with lattice vectors such that the position of the in-phase antinode of the light inside the interference region 670 substantially matches the position of the grating valleys or peaks. In some embodiments, third contact 893 is a transparent material (such as ITO) to pass redirected coherent light.

Fig. 6B shows a cross-sectional view of an exemplary grating-based laser device (hereinafter laser device) 662 with front-side modulation. Laser device 662 is similar to the laser device shown in fig. 6A, except that grating region 680 is located at the bottom of interference region 670. In fig. 6B, elements similar to those of fig. 6A are given the same numbers for simplicity, and these elements also have the same or similar materials/components/functions as shown in fig. 6A. Further, in the laser device 662 shown in fig. 6B, the first contact 691 and the second contact 692 are in contact with different epitaxially grown layers, so that the first contact 691 and the second contact 692 are located at different vertical layers. In some embodiments, the first electrode 691 is in contact with an N-type III-V semiconductor and the second electrode 692 is in contact with a P-type III-V semiconductor, wherein both the N-type and P-type materials are grown by MOCVD or MBE using in situ doping.

Fig. 6C and 6D show perspective views of exemplary grating-based laser devices (hereinafter laser devices) 663 and 664 having front surface modulation. The laser devices 663 and 664 are similar to the laser device shown in fig. 6A except that the arrangement of the quantum well structures inside the PEM 672 may be parallel (fig. 6D) or perpendicular (fig. 6C) to the carrier injection direction or resonance direction. Since in fig. 6C and 6D light passes through one of the electrodes (V3), the material for this electrode should be transparent to light. For example, if the third electrode 693 overlaps with a light emitting path, when an output light wavelength is longer than 850nm, an insulating material such as an oxide and a conductive material such as polysilicon may be used.

Fig. 6E and 6F show perspective views of exemplary grating-based laser devices (hereinafter laser devices) 665 and 667 having front modulation. The laser device 665 shown in fig. 6E has a similar quantum well orientation as that shown in fig. 6C, and the laser device 667 shown in fig. 6F has a similar quantum well orientation as that shown in fig. 6D, except that one of the terminals (e.g., the third electrode 693) is intentionally offset from the light emission direction to avoid blocking light. The material selection for the terminal can be more varied than those shown in fig. 6C and 6D.

Fig. 6G shows a perspective view of an exemplary grating-based laser device (hereinafter laser device) 668 with front modulation. The illustrated laser device 668 is similar to that of fig. 6A except that the two conducting electrodes 691 and 692 are in contact with different layers and the carrier injection direction (between 691 and 692) is different from the optical resonance direction (between the two electrodes 693) defined by the first and second reflectors 666 and 674. In this example, carriers are injected primarily from 691 and 692 and recombine to produce photons. Photons can resonate between the two reflectors 666 and 674 and be emitted through the grating region 680 in a similar mechanism as previously described. The modulating electrode 693 is far from the grating emission area to avoid blocking light. In some embodiments, grating region 680 may also function, in part, as part of a modulation electrode.

In some embodiments, the emission beam profile may be further modified based on changing the width/length ratio of the grating region as seen from above. The length may be defined as the direction along the direction of interference or resonance.

Fig. 7A shows a cross-sectional view of an exemplary grating-based laser (hereinafter laser device) 761 with back-side modulation. The laser device 761 is similar to that of fig. 6A except that a third contact 693 is formed on the bottom (back side) of the interference region 760 and coherent light is emitted from above (front side) the interference region 760 through the grating region 780 in a similar mechanism to that described previously. Although not shown in this figure, the first contact 791 and the second contact 792 may also be in contact with different epitaxially grown layers in a manner similar to that of FIG. 6B. In addition, grating region 780 can also be located at the bottom of interference region 760 in a manner similar to that of fig. 6B, as long as the directivity is designed accordingly. For a back side modulation with a front side emitting structure as shown here, the material composition of the modulation electrode can be more flexible since it does not overlap the light emitting path.

Fig. 7B and 7C show perspective views of exemplary grating-based lasers (hereinafter laser devices) 762 and 763 with back-side modulation. The laser device shown here is similar to that of fig. 6E and 6F in that the quantum well orientation inside the PEM 772 can be changed and the third modulation electrode 793 is in contact with the bottom of the interference region 770.

Fig. 8A shows exemplary simulation results of a cross-section of a grating-based laser device having two alternating grating structures. InGaAs quantum wells embedded in InP matrices were designed and simulated with the InGaAsP layer as the upper grating. The near field distribution shows that the grating peak of one grating structure matches the 0 ° in-phase antinode and the grating peak of the other grating structure matches the 180 ° in-phase antinode. Above the grating, a significant vertical emission of light in the upward direction can be observed, and the corresponding far field distribution shows a 0 ° far field angle, i.e. a complete vertical emission. The exemplary simulation shows an exemplary implementation of a grating-based laser device using two grating structures as shown in fig. 3A.

Fig. 8B shows exemplary simulation results (top view) of beam profiles according to different widths/lengths of the grating regions. Width/length may be defined as the direction perpendicular/along the interference direction. The waveforms may be different in these two directions due to their difference in confinement. In the example using the SOI substrate, the waveform in the width direction is similar to a sinusoidal function (weaker constraint), while the waveform in the length direction is similar to a rectangular function (stronger constraint). As a result, in this example, the width can be made larger than the length to achieve a circular emission beam profile.

FIG. 9 shows an example of an optical coupler 900 integrated with a p-n junction. Optical coupler 900 includes a first reflective region 906, an interference region 920, and a second reflective region 914. The interference region 920 includes a grating region 930. The first reflective region 906, the interference region 920, the second reflective region 914, and the grating region 930 can be implemented using any of the respective regions described herein.

Optical coupler 900 also includes a p-n junction pair including p-doped regions 921,923 and 925, and n-doped regions 931,933, and 935. Typically, by controlling one or more p-n junction pairs, parameters such as output power and output wavelength can be actively controlled by applying a voltage or carrier injection. In some embodiments, the p-n junction pairs 921/931,923/933 and/or 925/935 may extend into the first reflective region 906, the interference region 920, and/or the second reflective region 914, respectively, for better controllability. In some embodiments, the p-doped and n-doped regions may alternate to form an interdigitated pattern or other pattern. The description of the doped region may be applied to any of the optocouplers described in this application.

In some embodiments, the n-doped region 931 and the p-doped region 921 can be configured to provide an electric field in the first reflective region 906 by applying a voltage or a current across the n-doped region 931 and the p-doped region 921, wherein the first reflective region 906 can be configured to provide different reflectivities by applying a voltage or a current across the n-doped region 931 and the p-doped region 921.

In some embodiments, the n-doped region 935 and the p-doped region 925 can be configured to provide an electric field in the second reflective region 914 by applying a voltage or current across the n-doped region 935 and the p-doped region 925, wherein the second reflective region 914 can be configured to provide different reflectivities by applying a voltage or current across the n-doped region 935 and the p-doped region 925. As another example, the n-doped region 935 and the p-doped region 925 can be configured to provide an electric field in the second reflective region 914 by applying a voltage or current across the n-doped region 935 and the p-doped region 925, wherein electrical carriers in the second reflective region 914 can be extracted.

In some embodiments, the n-doped region 933 and the p-doped region 923 can be configured to provide an electric field in the interference region 920 by applying a voltage or current across the n-doped region 933 and the p-doped region 923, wherein the interference region 920 can be configured to provide different interference patterns for the interference light by applying a voltage or current across the n-doped region 933 and the p-doped region 923.

For example, by applying a reverse bias, the electric field can extract free carriers in the region, and thus the refractive index of the region can be changed. As another example, by applying a forward bias, free carriers may be injected into a region and thus the refractive index of the region may be changed.

Fig. 10A illustrates an exemplary photonic integrated circuit 1000 having multiple outputs. Photonic integrated circuit 1000 includes a first waveguide region 1002, first waveguide region 1002 configured to guide a wire in a direction indicated by arrow 1022. Photonic integrated circuit 1000 includes a first grating region 1020 formed on one side of interference region 1010. The photonic integrated circuit 1000 includes a second grating region 1021 formed on a different side of the interference region 1010, e.g., the opposite side as shown in fig. 10A. Photonic integrated circuit 1000 includes a reflective region 1014 and may optionally include another reflective region 1006. The photonic integrated circuit 1000 includes a second waveguide region 1028 that can be coupled to other passive and/or active optical components.

In some embodiments, light from the first waveguide region 1002 enters the interference region 1010 and may be directed to the first external medium 1030, the second external medium 1032, or the second waveguide region 1028. For example, similar to the description of fig. 9, the n-doped region and the p-doped region may be configured to provide an electric field in the interference region 1010 by applying a voltage or current across the n-doped region and the p-doped region, wherein a portion of light emitted in the + z direction and a portion of light emitted in the-z direction may be controlled by applying a voltage or current across the n-doped region and the p-doped region. As another example, similar to the description of fig. 9, the n-doped region and the p-doped region can be configured to provide an electric field in the second reflective region 1014 by applying a voltage or current across the n-doped region and the p-doped region. The reflectivity of the second reflective region 1014 can be adjusted and light can be transmitted to the second waveguide region 1028.

In some embodiments, light enters the interference region 1010 and may be split into different portions of light exiting the first external medium 1030, the second external medium 1032, and/or the second waveguide region 1028. For example, the grating in the first grating region 1020 may be designed such that the grating periodicity substantially matches the standing wave of TE polarized light. Similarly, the grating in the second grating region 1021 may be designed such that the grating periodicity substantially matches the standing wave of TM polarized light. By controlling the proportion of TE and TM polarized light in photonic integrated circuit 1000, the portion of light exiting photonic integrated circuit 1000 to first external medium 1030 and second external medium 1032 may be controlled. The above examples can be used as an efficient polarizing beam splitter.

In some embodiments, a first layer 1024 may be formed between the first grating region 1020 and the first external medium 1030. The first layer 1024 may be formed to protect the photonic integrated circuit 1000 or provide a certain distance for coupling the first grating region 1020 and the first external medium 1030. In some embodiments, the second layer 1016 may be formed between the second grating region 1021 and the second external medium 1032. The second layer 1018 may be formed to protect the photonic integrated circuit 1000 or to provide a certain distance for coupling the second grating region 1021 and the second external medium 1032. For example, first layer 1024 may be a cladding layer and second layer 1016 may be a substrate of photonic integrated circuit 1000. As another example, first layer 1024 may have a lower index of refraction than grating region 1020.

Fig. 10B shows an exemplary photonic integrated circuit 1001 with multiple inputs and outputs. The photonic integrated circuit 1001 may include a first waveguide region 1051, a second waveguide region 1052, a third waveguide region 1053, a fourth waveguide region 1054, p-n junctions 1055-. The structures of the first waveguide region 1051, the second waveguide region 1052, the third waveguide region 1053, the fourth waveguide region 1054, the p-n junction 1055-.

In some embodiments, light from the first and third waveguide regions 1051 and 1053 enters the interference region 1070 and may be directed to the second waveguide region 1052, the fourth waveguide region 1054, or exit the grating in the z-direction, as shown by outward arrow 1064. In some embodiments, to minimize back reflection of input light from the first and third waveguide regions, the reflectivities of the first and third reflective regions 1061 and 1091 may be adjusted during initial design, or by dynamically applying an electric field, to match the single-cycle attenuation coefficients of waves propagating in the x and y directions, respectively.

In some embodiments, light from first waveguide region 1051 enters interference region 1070 and may be split into different portions to second waveguide region 1052, third waveguide region 1053, fourth waveguide region 1054, and/or exit the grating in the z-direction, as shown by outward arrow 1064. For example, the grating region may comprise a two-dimensional grating 080 configured to split light into two light portions propagating in two directions x and y according to wavelength. As another example, the grating region may include a two-dimensional grating 1080 configured to split the light into two light portions propagating along two directions x and y, depending on polarization. As another example, the two-dimensional grating 1080 may be configured to inversely combine two light portions propagating along two directions x and y into one light portion.

In some embodiments, the two-dimensional grating 1080 can be configured to emit light upward in the z-direction by combining two lights from two directions x and y by having the period of the grating 1080 in the x and y directions substantially match the period of the interference pattern in the x and y directions, respectively. In some embodiments, the two-dimensional grating 1080 can be configured to emit light upward in the z-direction by combining two lights from two directions x and y, modifying the interference pattern in the x and y directions by applying an electric field between the p-doped and n-doped regions to match the grating 1080 pattern in the x and y directions, respectively. As another example, the two-dimensional grating 1080 may be configured to inversely split one light propagating along one direction (e.g., -z) into two light portions propagating along two directions x and y.

Similar to the description of fig. 10A, in some embodiments, the n-doped region and the p-doped region may be configured to provide an electric field in the interference region by applying a voltage or current across the n-doped region and the p-doped region, wherein the respective proportion of each of the two light portions propagating in the two directions is controlled by applying a voltage or current across the n-doped region and the p-doped region. For example, voltages may be applied across the n-doped region 1059 and the p-doped region 1056 to control the routing or splitting of the input light. In some embodiments, one or more doped regions may be eliminated if the refractive index of the respective regions does not need to be modulated. For example, doped regions 1056 and 1059 may be removed if it is not desired to dynamically modulate interference region 1070.

Fig. 11A shows an example of an optical device 1101 that includes an angled mirror 1102 that provides high reflectivity over a wide spectral range. The description of fig. 11A may be applied to any of the reflective regions disclosed in the present application. Generally, light propagates through the grating region 1120 and is incident on facets 1131a and 1131b of the angled mirror 1102. Since light is incident on the facets 1131a and 1131b beyond the angle of total reflection, a large amount of light is reflected due to total reflection, thereby achieving high reflectance.

Fig. 11B shows an example of an optical device 1103 that includes a circular or elliptical facet (facet)1104 that provides partial or high reflectivity. The description of fig. 11B may be applied to any of the reflective regions disclosed in the present application. Typically, light propagates through curved grating region 1112 and is incident on facet 1104. In some embodiments, the facets 1104 may be coated with a metal layer to provide high reflectivity. The curved facets 1104 refocus the light toward the waveguide region by passing the high reflectivity curved facets 1104.

Fig. 11C shows an example of an optical device 1105 including a bragg reflector 1106 that provides high reflectivity. For example, the bragg reflector 1106 may be formed of a DBR and/or DFB structure by full etching with a bragg period equal to half the wavelength, as shown in fig. 11C. The description of fig. 11C may be applied to any of the reflective regions disclosed in the present application. Typically, light propagates through the grating region 1122 and is incident on the DBR mirror 1106. In some embodiments, the DBR mirror 1106 may be designed to provide high reflectivity over a range of wavelengths.

Figure 11D shows an example of an optical device 1107 that includes facets 908 that provide partial reflectivity or high reflectivity. The description of FIG. 11D may be applied to any of the reflective regions disclosed in the present application, generally, light propagates through the grating region 1123 and is incident on the facet 1108. Without any additional coating, the reflectivity can be determined using the fresnel equation. In some embodiments, the facets 1108 may be coated with one or more layers of material to increase reflectivity. For example, the facets 908 may be coated with a metal layer to increase reflectivity. As another example, the facet 1108 may be coated with multiple dielectric layers to increase reflectivity over a range of wavelengths. As another example, facet 1108 may be coated with a quarter-wavelength dielectric layer followed by a metal layer to increase reflectivity over a range of wavelengths.

Fig. 11E shows an example of an optical device 1109 that includes a surface corrugated bragg reflector 1136 that provides high reflectivity. For example, the surface corrugated bragg reflector 1138 may be formed by partial etching from a DBR and/or DFB structure with a bragg period equal to half the wavelength, as shown in fig. 11E. The description of FIG. 11E can be applied to any of the reflective regions disclosed in the present application, and generally, light propagates through grating region 132 and is incident on mirror 1136 and reflected to form an interference pattern.

Any other type of reflector that can be integrated in a photonic integrated circuit may also be used as a reflector

An alternative to the reflectors depicted in fig. 11A-11E. As an example, the reflective region may alternatively comprise a waveguide ring mirror. As another example, the reflective region may instead comprise an anomalous dispersion mirror, wherein the effective refractive index of the dispersion mirror increases with longer wavelengths.

Fig. 12 shows an example of a flow chart for designing a grating-based optical transmitter. Process 1200 may be performed by a designer or a data processing apparatus, such as one or more computers.

The cavity material composition and scale are first determined (1202). In some embodiments, the scale and material composition for the cavity or substrate may be determined based on the target light polarization/mode/wavelength/spot size, and the external medium (e.g., optical fiber over grating or waveguide connected to the second side 114, etc.). For example, for single-mode optical signals with a center wavelength of about 1310nm, an InP layer may be used as the substrate, and quantum well structures based on InAs, InGaAs, InGaAsP, and InGaAsN may be used as the light source region above the InP substrate. Another InP layer may be used as a cladding layer over the light source area. If the spot size of the external fiber is about 10 μm, the size of the cavity aligned with the fiber direction needs to be about or larger than 10 μm to allow the external fiber to be coupled to the grating structure.

A reflector design is then determined (1204). An appropriate reflector design (e.g., tapered DFB/DBR or corner mirror or oxide-metal coating, etc.) can be used to form the interference wave pattern. In some embodiments, a numerical analysis tool, such as an FDTD simulation system, may optimize design parameters to produce a design of reflectors with near 100% reflection. For example, the design may be tapered waveguide Distributed Bragg (DBR) or Distributed Feedback (DFB) reflectors, each having a period equal to about half the effective wavelength of the light in the cavity. An interference region containing at least a portion of the interfering light is formed within the cavity.

Then, if a DFB/DBR reflector design is used, a quarter-wave phase shift discontinuity can be achieved to break the symmetry (1206). This allows only a single optical mode to be formed within the cavity.

A tapered structure may then be implemented on both sides of the quarter-wave phase shift discontinuity to gradually compensate for the local effective index mismatch caused by the discontinuity (1208).

A grating structure that emits light over the interference region may then be determined based on the interference light wave pattern inside the interference region (1210). The period of the grating pattern needs to substantially match the period of the interfering light; other parameters such as duty cycle, grating height and shape of the grating structure may be optimized according to parameters such as incident spot size, mode of light, wavelength of light, materials of the cavity and light source region and expected exit angle. In some embodiments using a DFB/DBR reflector design, the grating may include two grating structures arranged along the direction of light propagation with a 180 ° phase shift, as shown in fig. 3A. In some embodiments, one grating structure is formed by decreasing the duty cycle at some portion of one DFB reflector by a predetermined value, while the other grating structure is formed by increasing the duty cycle at some portion of the other DFB reflector by a similar predetermined value. By alternately decreasing and increasing the duty cycle by similar amounts at different regions of the DFB reflector, the overall effective reflectivity can be kept substantially constant, and thus the center wavelength of the interference wave pattern inside the interference region can also be kept substantially constant after these duty cycle adjustments. Two grating structures, each having a period substantially matching the period of the interfering light, may be used together as a reflector and an optical antenna to emit light in a substantially perpendicular direction. In some embodiments, the addition of a grating structure may still change the effective refractive index, and thus the characteristics of the interfering light may change. Therefore, some iterative process may be required for optimization.

An exemplary design flow has been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, various forms of the flows shown above may be used, with steps re-ordered, added, or removed. For example, in FIG. 12, steps 1206 and 1208 are optional, and if combined may also be done before step 1210. As another example, step 1206 may also be completed after step 1208 and by the same step 1208. As another example, steps 1204,1206, and 1208 may also be performed in the same step. As another example, step 1210 may also be completed before step 1204.

Fig. 13 shows an example of a flow chart for manufacturing a grating-based optical transmitter. Process 1300 may be performed by a system including data processing apparatus, such as one or more computers controlling one or more devices performing manufacturing steps.

The system is used to fabricate a light source region (1302) containing quantum wells or quantum wire or quantum dot structures on a substrate. Fabrication of the source region may be accomplished by fabrication techniques including Molecular Beam Epitaxy (MBE) or metalorganic chemical vapor deposition (OCVD). In some embodiments, the cladding layer may be further deposited by a film deposition technique such as chemical vapor deposition, air gap enhanced chemical vapor deposition, sputtering, or any other suitable thin film deposition technique that may be used to deposit one or more layers over the light source region.

The system is used to fabricate gratings (1304). The fabrication of the grating may be accomplished by a combination of fabrication techniques including photolithography, etching, and deposition. For example, a lithography technique such as projection lithography with a step lithography tool, electron beam lithography, contact lithography, or any other suitable lithography technique may be used to pattern the grating. As another example, the patterned grating may be etched using an etching technique such as dry etching, wet etching, or any other suitable etching technique. The single grating structure or the two grating structures mentioned in fig. 3A can be manufactured by sharing the lithography and etching steps using the same mask. Furthermore, if a surface corrugated DFB type reflector is used, the surface corrugated structure can also be completed in the same step as when the grating is manufactured. In some embodiments, the grating further comprises a quarter-wave phase shift and taper structure as previously mentioned. In some embodiments, one or more layers of material may be deposited on the grating as a cladding layer using thin film deposition techniques, such as chemical vapor deposition, air gap enhanced chemical vapor deposition, sputtering, or any other suitable thin film deposition technique.

The system is used to fabricate a chamber (1306). Fabrication of the cavity may be accomplished by photolithography and etching to define the cavity to a target size. In some embodiments, one or more layers may optionally be deposited using thin film deposition techniques to passivate the patterned cavities.

The system is used to manufacture a reflector (1308). The fabrication of the reflective region may be accomplished by a combination of photolithography, etching and deposition similar to that described previously. In some embodiments, the DBR type or corner reflectors can be formed during the same step in forming the cavity by sharing the same photolithography, etching steps, or even masks (1306). In some embodiments, the metal reflector may be formed by depositing a metal layer on the sides of the cavity along the direction of the interfering light. In some other embodiments, a quarter-wave dielectric layer may be formed between the cavity and the metal layer to achieve high reflectivity.

The system is used to fabricate electrodes to provide electrical carriers into the light source region or to modulate an electric field in the light source region (1310). At least two electrodes electrically coupled to the light source region are formed by a combination of deposition, photolithography, and etching. In some embodiments, the third electrode is formed such that three electrodes are arranged to provide control of the relative electric field between the three electrodes to modulate the electrical carrier concentration. Light generated by recombination of the electric carriers resonates within the interference region in a first direction and exits the interference region in a second direction different from the first direction.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, various forms of the flows shown above may be used, with steps re-ordered, added, or removed. For example, step 1306 may also be completed before step 1304. As another example, step 1308 may also be accomplished with the same step 1304. As another example, step 1308 may also be accomplished with the same step 1306. As another example, step 1310 may also be completed after step 1302.

Optical device for redirecting incident electromagnetic waves

Structure with one mirror on one side:

fig. 14A shows a block assembly of a first embodiment of an optical device for redirecting incident light. Optical device 1400 generally includes a chamber 1410 having a first side 1412, a grating structure 1420 disposed on a top surface 1418 of chamber 1410 or embedded in chamber 1410, and a mirror 1416 disposed on first side 1412. The above-described components may be disposed on a support layer 1432 having a refractive index lower than that of the cavity to produce total internal reflection, e.g., silicon dioxide layer 1432 adjacent to cavity 1410 comprises silicon or silicon nitride or silicon oxynitride thereon, or silicon dioxide layer 1432 adjacent to cavity 1410 is comprised of silicon dioxide doped thereon. The above components may also include silicon or germanium or nitride or oxide or polymer or glass or a combination thereof, and may be disposed on a highly reflective layer 1432, such as an oxide-metal coating or a Distributed Bragg Reflector (DBR) stack.

Assuming that the light 1440 is incident on the left half of the cavity 1410 (i.e., the portion opposite the first side 1412), as shown by the arrows, the incident light is substantially attenuated if it is considered to be confined inside the cavity 1410 during a single cycle from the initial entry point to the first side 1412 and then back to the initial entry point.

This situation may be further explained where the initial point of incidence has a reflectivity r for light from its left side, and the cavity (defined between the initial point of entry and the first side 1412) has a single-cycle attenuation coefficient α. In this case, under the light constraint "α ═ r", α needs to be 0 as r is now 0 (no light reflection at the initial entry point), which means that all light energy is attenuated after a single cycle. At this point, the optical confinement condition refers to spatially positioning light in the cavity region by substantially zero back reflection; a single cycle refers to light traveling from an initial entry point into the cavity 1410, reaching the first side 1412, reflecting off of the mirror 1416, and finally returning to the initial entry point.

In practical situations, this embodiment still works but with different coupling efficiency when slight deviations from the ideal "α ═ r" situation occur. Since many non-ideal factors such as process variations and material non-uniformities generally play a role in practical implementations, deviations from the exact conditions are expected in practical implementations. However, as long as these deviations are within the design tolerances, they do not change the function of the embodiment. Therefore, making design choices under imperfect conditions is part of the "optimization" process. For example, if overetch occurs during the grating etch process, the duty cycle of the initial design (where duty cycle is defined as the ratio of the peak width of the grating to the sum of the peak width and the valley width along the wave propagation direction) may be increased to compensate for the overetch. All such design choices and variations are also within the scope of this embodiment if such choices are made while still following the concept of this embodiment. This statement also applies to structures discussed in the following section that have mirrors on both sides. Viewed from another perspective, this mirror configuration can be considered as one of the special cases of a two-mirror configuration, where the reflectivity of one mirror is equal to zero.

For the design of the grating structure 1420, by substantially matching the pattern of the grating structure 1420 to the standing wave pattern in the cavity 1410, a large portion of the incident light may pass through the grating structure 1420, exiting the cavity 1410 either upward or downward at a predetermined angle relative to the direction of incidence. By adjusting the grating height or duty cycle or the cladding covering the grating structure or layer 1432, or a combination thereof, the directivity can be modified such that almost all power is emitted upwards while almost no power is emitted downwards, or vice versa. For simplicity of description, and not to limit the scope, upward transmission is described as the primary case throughout the specification. As shown in fig. 2, the symbol d1 represents the distance (intensity periodicity) between two adjacent maximum power points of the standing wave in the cavity 1410, and the symbol d2 represents the period of the grating structure 1420 (a rectangular grating is shown in this figure). The theoretical matching condition is d2 ═ 2d 1. By matching the waveform pattern, the grating structure 1420 acts as an "antenna" and becomes most efficient for light exiting the cavity 1410 upward at a predetermined angle relative to the initial incident direction. All point source wavefronts emanating from each periodic segment (p1 and p2) are combined into a joint planar wavefront that propagates upward at a predetermined angle based on the topographical design of grating structure 1420, such as its shape, period, duty cycle, depth/height, or their combined characteristics. In the field of optical coupling, the predetermined angle may be designed to be substantially perpendicular to the top surface of the cavity to facilitate coupling light to/from the external optical component.

The actual matching conditions may deviate from the theoretical conditions d 2-2 d1 due to the presence of some non-ideal factors such as cavity etching changing the effective reflectivity and the etching process itself unnecessarily creating straight line topography. Thus, while the theoretical matching condition is d 2-2 d1, during actual implementation, slight deviations from the exact condition are expected. For example, the distance d1 between two adjacent maximum power points of the standing wave in the cavity 1410 and half of the period d2 of the grating structure 1420 do not match exactly, but still have nearly the same order of magnitude. In other words, the distance d1 between two adjacent maximum power points of the standing wave in the cavity 1410 and half of the period d2 of the grating structure 1420 are substantially within the same order of magnitude. For the definition of "same order of magnitude", two numbers have the same order of magnitude if the ratio between the larger number and the smaller number is smaller than 10. Other parameters such as grating duty cycle, depth/height, and shape of the grating structure are design parameters, and these choices depend on factors including the incident light polarization/mode/wavelength/spot size, the cavity material, and the desired directionality of the output light. All of the choices of the above parameters may affect performance but, if chosen appropriately, do not change the basic functionality. These choices are therefore part of the "optimization" process based on the above concept.

Fig. 15A shows one of working examples for explaining the feasibility of the embodiment shown in fig. 14A. Optical device 1400 includes a chamber 1410 having a first side 1412, a grating structure 1420 disposed on a top surface 1418 of chamber 1410 or embedded in chamber 1410. A mirror 1416 is disposed at the first side 1412. The mirror 1416, for example, provides near 100% (typically, a high reflectivity is expected, such as above 50% to minimize power leakage outside the first side 1412 to achieve the optical confinement condition). Cavity 1410 may be disposed on support layer 1432, for example, and support layer 1432 is disposed on substrate 1430. The index of refraction of support layer 1432 is lower than the index of refraction of the cavity to create total internal reflection, e.g., silicon dioxide layer 1432 adjacent to cavity 1410 comprises silicon or silicon nitride or silicon oxynitride thereon, or silicon dioxide layer 1432 adjacent to cavity 1410 comprises silicon dioxide doped therewith. Light is incident from the direction shown by arrow 1440 and enters the cavity 1410 through the initial entry point. The grating length L1 may be, for example, about 10 μm to better match a conventional Single Mode Fiber (SMF) mode profile. Other dimensions may be selected based on the dimensions of the external optical component to which the grating structure is intended to be coupled. Exemplary grating structure 1420 can be, for example, a rectangular rib, having a period of 420nm, a duty cycle of 0.56, and a height of 175nm, where the duty cycle is in the direction of wave propagation, the ratio of the peak width to the entire period (the entire period is the sum of the peak width and the valley width), and the height is in the direction perpendicular to top surface 1418.

Simulation results show that at a wavelength of 1305nm with parameters chosen as shown above, directivity through the grating up to about 85% to 88% can be obtained with approximately low back reflection. To calculate the total coupling efficiency, a standard SMF (optical fiber coated with an anti-reflection coating) was placed on top of the grating. A Transverse Electrical (TE) optical signal is then injected into the cavity 1410 from an initial entry point, shown by 1440, and redirected into the SMF. The corresponding minimum total coupling loss was calculated to be about 1.25dB at a wavelength of 1305nm and has a full width of 3dB of about 20nm to 25 nm.

Note that the above numerical examples are described to demonstrate the feasibility of the present disclosure, and should not be considered limiting in any way. Other variations and optimizations are considered to be within the scope of this description, as long as they are covered in the claims set forth in this disclosure.

A structure with two mirrors on two opposite sides:

fig. 14B shows a block assembly of a second embodiment of an optical device for redirecting incident light. The optical device 1400 mainly includes components similar to those shown in fig. 14A; therefore, for simplicity of description, similar components are given the same reference numerals. In the embodiment shown in fig. 14B, the optical device 1400 further includes a light reflector 1417 (which may also be referred to as a second mirror M2 for ease of illustration) at the second side 1414 of the cavity 1410.

Assuming light is also incident from the left half of the second side 1414, as shown by 1440, the incident light may be considered to be confined within the cavity 1410 if certain design conditions are met. The material/dimensions of the cavity 1410, the reflectivity of the mirror 1416 at the first side 1412 (which may also be referred to as the first mirror M1 for ease of illustration), and the reflectivity of the light reflector 1417 at the second side 1414 are selected such that the reflected light where the initial light enters and all light from the right side of the second side 1414, transmitted through the light reflector 1417 and entering the left side of the second side 1414 destructively interfere with each other at the left side of the second side 1414 due to pi phase differences at resonance conditions inside the cavity to achieve theoretical light confinement conditions. Since the power leaking out of the cavity 1410 (from all its surroundings, such as its bottom, left and right sides in this 2D example) is controlled by destructive interference under this condition based on the disclosed design concept, the most efficient way for light to leave the cavity 1410 is through the grating structure 1420. By substantially matching the pattern of the grating structure 1420 to the pattern of the standing wave in the cavity 1410, a large portion of the incident light exits the cavity 1410 upward through the grating structure 1420 by a topographical design based on the grating structure 1420, such as its shape, period, duty cycle, and depth/height angle. In the field of optical coupling, the angle may be designed to be substantially perpendicular to the top surface of the cavity for ease of coupling.

The first side 1412 and the second side 1414 shown in fig. 14B are illustrated with dashed and dotted lines. Thus, the optical structure above support layer 1432 may be comprised of multiple optical waveguide regions that are integrally formed or in one piece with each other. For example, light having a particular wavelength impinges a first waveguide region of an optical device and propagates to a second waveguide region coupled to the first waveguide. The second waveguide region is coupled to the interference region, wherein light having the particular wavelength is reflected at the first reflectivity between the second waveguide region and the interference region. The interference region is coupled to the third waveguide region, wherein light having the specific wavelength is reflected between the interference region and the third waveguide region with the second reflectivity. The grating structure 1420 may be disposed on or embedded in the interference region. In some embodiments, the first reflectivity and the second reflectivity may vary with wavelength. In some embodiments, the first reflectivity and the second reflectivity are constant over a range of wavelengths.

Hereinafter, the physical principles of the optical confinement mechanism are further explained by using hypothetical numerical examples. Assume that light enters the cavity through a photo-reflector 1417(M2) at the second side 1414. Before that, the optical power is set to 1. If 10% M2 is designed (r ═ 10%), the transmitted light power becomes 90% after passing through M2. Under the constraint "α ═ r", α, which is the light intensity single cycle attenuation coefficient, was designed to be 10%. At this point, single cycle refers to light traveling from the second side 1414 through the cavity 1410 to the first side 1412, by the mirror 1416(M1), and finally back to the second side 1414, but not yet reflected by M2. M1 was designed to have 100% reflectivityIs a perfect reflector. The optical power then becomes 90% 10% 9% before the light passes through the cavity 1410, reflects from M1 and makes another pass through the cavity 1410 before again passing through M2. At the interface between M2 and cavity 1410, since M2 is typically a reciprocal structure, 9% by 10% to 0.9% of the optical power will be reflected back into the cavity, while 8.1% of the optical power will pass through M2 and exit cavity 1410. Referring to FIG. 19A, the light intensity is I before entering the lumen₀And after the first single cycle, the light intensity becomes I before passing back through M2_a＝I₀(1-M2R)(M1R)α_cWherein M2R is the reflectance of M2, M1R is the reflectance of M1, and the single-cycle attenuation coefficient is α ═ M1R α_cIn which α is_cIs the net attenuation coefficient introduced by the cavity, excluding the effect of M1. The intensity of the backward transmitted light through M2 then becomes I_b＝I_a(M2R)。

Although in this example, the portions of light returning from the photo-reflector 1417 to the incident source after the zero and first passes are 10% and 8.1%, respectively, they are out of phase at the resonant conditions within the cavity, and therefore the actual power leaking out of the cavity 1410 from the second side 1414 is less than the sum of 10% and 8.1%. Under light constraints and after multiple passes, all light returning from the photo-reflector 1417 to the incident source cancels out each other due to destructive interference, which means that almost all of the power of the original incident light is diverted into the cavity 1410 and then redirected upward at a predetermined angle. As shown in FIG. 19B, under the constraint, the retro-reflected light power I outside the cavity after multiple passes_ESubstantially reaching zero.

Since the single-cycle attenuation coefficient α is a function of M1R, in order to satisfy the optical constraint "M2R ═ α", the reflectivity of M2R must be less than the reflectivity of M1R, as long as the cavity is lossy. It is also noted that for simplicity of description, it is assumed that the phase shift introduced by M2(θ M2) is zero, so that the actual resonance condition "round-trip phase shift equals 2M π" (M: integer) is the same as "single-cycle phase shift equals 2M π". If θ m2 is not zero, the resonance condition becomes "θ m2+ θ oc ═ 2m pi", where θ oc is a single cycle phase shift.

Fig. 15B shows one of the working examples further illustrating the feasibility of the embodiment shown in fig. 14B. The optical device 1400 includes a chamber 1410 having a first side 1412 and a second side 1414, a grating structure 1420 disposed on a top surface 1418 of the chamber 1410. A mirror 1416 is disposed at the first side 1412 and a light reflector 1417 is disposed at the second side 1414. The mirror 1416 is, for example, a tapered DBR mirror. The light reflector 1417 is, for example, a single etched slit. Light is incident from the left side of the photo-reflector 1417 and enters the cavity 1410 through the second side 1414. The grating structure 1420 is, for example, rectangular, with a period of 420nm, a duty cycle of 0.54-0.56, and a height of 180-185 nm. In this example, the light reflector 1417 is a slit with a width below 70nm to provide a mirror loss below 5%.

Assuming slit grating distances and slit widths of about 180 nm-188 nm and 38 nm-40 nm, directivity up through the grating of about 85% -87% can be simulated at wavelengths of 1305 nm-1310 nm by low back reflection. The minimum total coupling loss is calculated to be about 1.1-1.4dB at wavelengths of 1305nm to 1310nm and is characterized by a 3dB full width of about 20 nm. Furthermore, the slit width may also vary depending on design choice, and is preferably less than three effective optical wavelengths, as deduced from the incident wavelength and the refractive index of the material it travels. Other embodiments, for example, a tapered DBR reflector (such as the tapered DBR reflector 1417 shown in fig. 16F) may also be used as the light reflector 1417. Thus, the single slit example described above should not be considered a limiting case for implementing the light reflector 1417.

Note that according to another embodiment, a separate region may be inserted between the left boundary and the second side 1414 of the grating structure 420, or between the grating structure 1420 and the first side 1412, where the waveguide taper acts as a mode filter.

Even though the rib of the grating structure 1420 (e.g., the grating structure 1420 shown in fig. 14B) shown in the above-described embodiment has the sidewall 1420a perpendicular to the top surface of the cavity 1410, the rib of the grating structure 1420 may have the sidewall 1420a inclined to the top surface of the cavity 1410 in a non-perpendicular manner. For example, the angle of inclination, height/depth of the sidewalls, or spacing of the grating structures may be designed to modify the angle of emission of light to a predetermined angle relative to the top surface 1418. The grating structure 1420 may also have diagonal ribs and vertical ribs.

Furthermore, as shown in FIG. 15C, instead of ribs protruding from the top surface 1418 of the chamber 1410, the grating structure 1420 may be implemented by grooves that penetrate into the top surface 1418 of the chamber 1410. These grooves may penetrate into the chamber 1410 at a vertical angle, as shown in fig. 15C, or at an oblique angle, depending on the actual process conditions. Although the grooves are illustrated as having a shallower depth than the slots 1417, it should be noted that the grooves may have a deeper or the same depth than the slots 1417. The grooves may be distributed at uniform or non-uniform intervals.

Further, even though the rectangular ribs shown in fig. 15B and 15C have uniform periods and duty ratios, they may be non-uniform depending on the application scenario. For example, the period and duty cycle of the grating structure in the two side regions of the cavity are different from the period and duty cycle of the grating structure in the middle region of the cavity to better match the gaussian spatial intensity distribution of the SMF.

Note that the above examples (including the numerical parameters used) are described to demonstrate the feasibility of the present disclosure, and should not be considered in any way as the only way to implement the present disclosure. Other variations and optimizations should be considered within the scope of the present disclosure as long as they are encompassed by the claims set forth in the present disclosure.

Design process

In some embodiments, the design method may be described as follows:

the size and material of the cavity and the substrate may be determined based on the target light polarization/mode/wavelength/spot size, and the coupling device (e.g., fiber over grating or waveguide connected to the second side 1414, etc.). For example, for a single mode optical signal with a center wavelength of about 1310nm, a Si layer cavity of about 250nm above the oxide layer may be used. If the spot size of the external fiber is about 10 μm, the cavity needs to be about or larger than 10 μm in size to allow the fiber to be coupled to the grating structure that will later be formed on or embedded in the cavity.

Then, an appropriate mirror design (e.g., a tapered DBR or corner mirror or oxide metal coating, etc.) with a relatively high reflectivity is selected as the mirror 1416 and determines the interference wave pattern within the cavity.

The grating structure 1420 over the cavity 1410 is then designed based on the initial interference wave pattern. Note that adding gratings changes the cavity properties and may slightly change the internal interference waveform, so some iterative process may be required for optimization.

Then, based on the material mass and physical dimensions of the cavity 1410 and the grating structure 1420, the single-cycle attenuation coefficient (α) and the corresponding phase shift for the resonance condition can be calculated.

After obtaining the single-cycle attenuation coefficient α, an appropriate reflector design is selected with a reflectivity r ═ α (or very close to α), and placed at the second side 1414 as a light reflector 1417. Note that in the case where the single-cycle attenuation coefficient α is small or close to 0, the corresponding reflectance r may be set to zero, meaning that the photo-reflector 1417 is not present.

To better describe this particular case where r is 0, the design method with one mirror (i.e., mirror 1416) can be further described as follows:

the dimensions and materials of the cavity and substrate may be determined based on the target light polarization/mode/wavelength/spot size, and the coupling device (e.g., fiber optic over grating or waveguide connected to the second side 1414, etc.).

Then, an appropriate mirror design (e.g., a tapered DBR or corner mirror or oxide metal coating, etc.) with a relatively high reflectivity is selected as the mirror 16 and determines the interference wave pattern within the cavity.

The grating structure 1420 over the cavity 1410 is then designed based on the initial interference wave pattern. Note that adding gratings changes the cavity properties and may slightly change the internal interference waveform, so some iterative process may be required for optimization.

Then, based on the material mass and physical dimensions of the cavity 1410 and the grating structure 1420, the single-cycle attenuation coefficient (α) and the corresponding phase shift for the resonance condition can be calculated.

Based on the above design methodology, an exemplary digital design process for implementing a high performance coupler with substantially vertical launch on an SOI substrate is shown below. An optical simulation tool may be used to test the following design process:

a waveguide rearview mirror (i.e., mirror 1416) with characteristics close to 100% reflection is designed. This may be a silicon tapered waveguide DBR, a silicon waveguide ring mirror, a silicon corner mirror, or a silicon oxide metal coating.

The optical signal is transmitted into the waveguide using a waveguide rearview mirror. The interference wave pattern is observed and the effective wavelength is identified.

A grating structure is added to the waveguide such that the grating period is almost the same as the period of the interference wave pattern. Note that the grating length, for example, can be chosen to be comparable to the size of the outcoupling optics, e.g. SMF.

The grating parameters, such as shape, period, duty cycle, and depth/height, are fine-tuned until both the desired directivity (i.e., "power covered" divided by "power covered plus substrate power") and the desired far-field angle (e.g., substantially vertical emission) are achieved.

The single-cycle attenuation coefficient and its phase shift are measured and then a waveguide front light reflector (i.e., light reflector 1417) is designed with a reflectivity that matches the single-cycle attenuation coefficient (r ═ α). It can then be checked by the total back reflection of the entire structure whether the light constraint is fulfilled.

In the above example, the mirror 1416 may be implemented by a tapered waveguide DBR. The DBR is made up of fully etched slits having spatial widths equal to 50nm, 100nm, 175nm, 250nm, 234nm x 4 and line widths equal to 167nm, 150nm, 133nm, 116nm, 107nm x 3. Broadband reflection-100% covering a wavelength span of >200nm can be obtained by this setup. Next, with a waveguide rearview mirror, the TE light signal is sent into the waveguide to identify the effective wavelength. The grating period of 420nm was chosen based on the interference wave pattern, and the grating length 10 μm was chosen for later coupling to standard SMF. To avoid scattering at the grating-waveguide boundary, a fin-shaped grating is applied, which is located on the SOI waveguide.

The near field and far field patterns of the disclosed optical device indicate that a uniform plane wave with a substantially zero far field angle can be achieved. The strong field strength in the grating region indicates the cavity effect. In fact, the disclosed optical device can be considered similar to an "optical antenna" array, where all emitters are phase locked, so directional emission occurs at zero far field angle.

Furthermore, the grating structure parameters, including its shape, period, duty cycle and depth/height, can be adjusted individually or collectively to optimize directionality and far field angle. For example, the duty cycle may be modified on the side near M1 and M2 to achieve different directivities. Another example is to modify the period and etch depth to achieve different far field angles. Note that the above examples are described to demonstrate the feasibility of the present disclosure, and should not be construed as limiting. Other variations and optimizations should be considered within the scope of the present disclosure as long as they are encompassed by the claims set forth in the present disclosure.

In addition to the above embodiments, the optical device further has a derivative. FIG. 16A illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16A has similar components to those shown in fig. 15B; accordingly, for the sake of brevity, similar components are given the same (or similar) reference numerals. The optical device shown in fig. 16A uses a metal or dielectric coating 1416A on the side surface of the cavity 1410 in place of the tapered DBR mirror 1416 shown in fig. 15B.

FIG. 16B illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16B has similar components as those shown in fig. 15B; accordingly, for the sake of brevity, similar components are given the same (or similar) reference numerals. The optical device shown in fig. 16B uses a metallic or dielectric coating 1416A separated from the sides of the cavity 1410 by an air gap 1416B, instead of the tapered DBR mirror 1416 shown in fig. 15B.

FIG. 16C illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16C has similar components as those shown in fig. 15B; accordingly, for the sake of brevity, similar components are given the same (or similar) reference numerals. The optical device shown in fig. 16C uses a metal coating 1416A separated from the sides of the cavity 1410 by a dielectric layer 1416C, instead of the tapered DBR mirror 1416 shown in fig. 15B.

FIG. 16D illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16D has similar components as those shown in fig. 15B; accordingly, for the sake of brevity, similar components are given the same (or similar) reference numerals. In addition, for better illustration of the mirror used in this example, the substrate 1430 and the support layer 1432 are omitted here for simplicity. The optical device shown in fig. 16D uses a corner mirror 1416D having a light reflective side 1416E at the first side 1412 of the cavity 1410 due to total internal reflection instead of the tapered DBR mirror 1416 shown in fig. 15B. Note that the angled mirror 1416D may be integral with the chamber 1410 or integral with the chamber 1410. In some embodiments, the second mirror 1417 can be replaced with a propagation region where light propagates without reflection or loss.

FIG. 16E illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16E has similar components as those shown in fig. 16D. In the embodiment shown in FIG. 16D, the ribs in grating structure 1420 lie along substantially parallel lines, and the parallel lines are substantially perpendicular to the direction of propagation of the light. In the embodiment shown in fig. 16E, the grooves in grating structure 1420 lie along substantially curved lines (e.g., circular or elliptical lines having a common focus). Furthermore, even though the mirror 1419 is illustrated at the circumference of the fan-shaped grating structure 1420, one skilled in the relevant art may readily replace the mirror 1419 with other types of reflective devices, such as a tapered DBR mirror.

FIG. 16F illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16F has similar components to those shown in fig. 15B, except that the first mirror 16 and the second mirror 1417 each employ a tapered DBR mirror.

FIG. 16G illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16G has similar components as shown in fig. 16D, except that the second mirror 1417 in fig. 16G is a tapered DBR mirror.

FIG. 16H illustrates a block assembly of an optical device for redirecting incident light according to yet another embodiment. The optical device shown in fig. 16H has similar components to those shown in fig. 16D, except that the first mirror in fig. 16D is represented by a smooth surface, which may then be coated with other reflective layers to increase reflectivity.

The grating structure 1420 can be implemented using various designs, for example, a rectangular or triangular cross-section implemented in a single column, array, or segment, as shown in fig. 17A (symmetric triangular ribs), 17B (rectangular ribs), 17C (arrayed point ribs), 17D (ordered or random number of triangular ribs per row), and 17E (segmented ribs) as viewed from above. Fig. 17F to 17J are respective cross-sectional views of fig. 17A to 17E. Note that by changing the design of the grating structure, the emitted far field angle and directivity can be tuned. Other shapes may also be used as long as the distance d1 between two adjacent maximum power points of the standing wave in the cavity 1410 and half of the period d2 of the grating structure 1420 are of the same order of magnitude.

Further, the protruding ribs in the embodiment shown in fig. 17A to 17J may be replaced by correspondingly shaped penetrating grooves (symmetrical triangles, rectangles, lattice shapes, asymmetrical triangles, and segments), and these modifications are also within the scope of the present disclosure.

Fig. 18A to 18C show several simplified perspective views of an optical device to further illustrate the optical path for various application scenarios. The optical device shown in FIG. 18A has a block assembly similar to that shown in FIG. 14B; thus, the optical device shown in fig. 18A can be considered as one of the possible 3D perspective views. More specifically, the cavity 1410 has a first side 1412 with a mirror, a second side 1414 with a light reflector, and two sides 1413a and 1413b connected between the first and second sides 1412 and 1414, respectively. The grating structure may be embedded on the top surface 18a or the bottom surface 1418 b. Further, since the purpose of fig. 18A to 18C is to explain the optical path, the structures of the mirror, the reflector, and the grating are not shown at this time for the purpose of simple observation. The solid arrows in the figure represent the primary light propagation path, while the dashed arrows illustrate the secondary optical path when the directivity is not tuned to 100%. Fig. 18A shows an exemplary optical path, where light is incident from the second side and most of the light is redirected upwards by an angle of substantially 90 ° with respect to the incident direction. FIG. 18B is similar to FIG. 18A, but with a different grating design on 1418A or 1418B to provide other emission far field angles. In this figure, θ 1 is equal to θ 2, which is a result of the cavity effect. For example, when θ 1 is 45 °, θ 1 is also substantially 45 °. Further, fig. 8C shows a case when the grating structure is designed in such a manner as to have an asymmetric shape, for example, to emphasize one direction as indicated by a solid-line arrow (θ 1) rather than the other direction (θ 2) as indicated by a broken-line arrow. For simple viewing purposes, the dashed arrow indicating the secondary optical path (when the directivity is not adjusted to 100%) is not shown here. Many other possible light redirection scenarios are possible in conjunction with the reciprocal nature of this structure, so the examples shown here are for illustrative purposes and should not be taken as limiting the scope of the present disclosure. Other variations should be considered within the scope of the disclosure as long as they are encompassed by the claims set forth in the disclosure.

For purposes of ease of description and illustration, various embodiments may be discussed using two-dimensional cross-sections. However, three-dimensional deformations and derivations should also be included within the scope of the present disclosure as long as there is a corresponding two-dimensional cross-section in the three-dimensional structure.

The embodiments and all of the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments may be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a combination of substances that affect a machine-readable propagated signal, or a combination of one or more of them. The computer readable medium may be a non-transitory computer readable medium. The term "data processing apparatus" includes all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the described computer program, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

A computer program (also known as a program, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or one or more mass storage devices operatively coupled to receive data from or transfer data to, or both. However, a computer need not have such a device. Furthermore, the computer may be embedded in another device, e.g., a tablet, a mobile phone, a Personal Digital Assistant (PDA), a mobile audio player, a Global Positioning System (GPS) receiver, to name a few. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments may be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other types of devices may also be used to provide for interaction with a user; for example, feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including acoustic, speech, or tactile input.

Embodiments may be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the disclosed technology, or any combination of one or more such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network ("LAN") and a wide area network ("WAN"), such as the Internet.

The computing system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

While this specification contains many specifics, these should not be construed as limitations, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, but rather should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

Thus, particular embodiments have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results.

It is noted that any and all of the above-described embodiments may be combined with each other, except as otherwise noted above or where any such embodiments may be mutually exclusive in function and/or structure.

Although the present invention has been described with reference to specific exemplary embodiments, it should be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Claims (29)

1. An optical device, comprising:

a light source region configured to generate light;

first and second reflective regions configured to reflect the generated light such that interference light is formed in a first direction;

an interference region formed between the first and second reflective regions and coupled to the light source region, and configured to confine at least a portion of interference light formed in the first direction by light reflected between the first and second reflective regions; and

a grating region comprising a first grating structure and a second grating structure having substantially the same period but different duty cycles, wherein the two grating structures are arranged with a 180 ° phase shift along the first direction,

wherein the grating region is formed on a region that confines at least a portion of the interfering light and is configured to emit at least a portion of the light in a second direction different from the first direction,

wherein a quarter-wavelength offset region is formed in the grating region by removing or adding at least one section of the grating structure.

2. The optical device of claim 1, wherein a grating periodicity of the first grating structure substantially matches a periodicity of the interfering light within the interference region.

3. The optical device of claim 1, wherein a tapered region is formed adjacent to the quarter-wavelength offset region along the first direction, wherein a period or duty cycle of the tapered region increases or decreases from a side closer to the quarter-wavelength offset region toward a side away from the quarter-wavelength offset region.

4. The optical device of claim 1, wherein the first reflective region is a surface corrugated grating structure forming distributed feedback or distributed bragg reflection.

5. The optical apparatus of claim 4, wherein a duty cycle of the first grating structure of the grating region is different from a duty cycle of the surface corrugated grating structure of the first reflective region, and a period of the first grating structure is twice a period of the surface corrugated grating structure.

6. The optical device of claim 4, wherein the first grating structure of the grating region is formed on the same plane as the surface corrugated grating structure of the first reflective region.

7. The optical device of claim 1, wherein the light source is at least partially embedded in the interference region and comprises alternating III-V material layers forming a quantum well or quantum wire or quantum dot structure.

8. The optical device of claim 1, wherein a portion of the grating region is formed on the interference region or the first reflective region.

9. The optical apparatus of claim 1, wherein the second direction is substantially perpendicular to the first direction.

10. The optical device of claim 1, wherein the first grating structure region has a grating period of d2, wherein the intensity period of the interfering light within the interference region is d1, wherein d2 is substantially equal to 2 x d 1.

11. The optical apparatus of claim 1, wherein the grating region has a grating length along the first direction and a grating width along a third direction perpendicular to the first direction in a plane, and the grating width is different from the grating length to obtain a circular beam profile.

12. The optical apparatus of claim 1, further comprising:

an n-doped region and a p-doped region configured to provide an electric field in the interference region by applying a voltage or current across the n-doped region and the p-doped region,

wherein the interference region is configured to provide different interference patterns for the interference light by applying a voltage or current across the n-doped region and the p-doped region.

13. The optical apparatus of claim 1, further comprising:

an n-doped region and a p-doped region configured to provide an electric field in the first and/or second reflective region by applying a voltage or current across the n-doped region and the p-doped region,

wherein the first and/or second reflective regions are configured to provide different reflectivities by applying a voltage or current across the n-doped region and the p-doped region.

14. The optical device of claim 1, wherein the first or second reflective regions comprise one of: corner mirrors, DBR mirrors, DFB mirrors, anomalous dispersion mirrors, waveguide ring mirrors, dielectric layers with metallic mirrors, metallic layers.

15. The optical device of claim 1, wherein the grating region is formed with lattice vectors such that the position of an in-phase antinode of the interfering light within the interference region substantially matches the position of a grating valley or peak.

16. The optical apparatus of claim 1, further comprising:

first and second electrodes electrically coupled to the light source region, the first and second electrodes configured to generate light by electrical carrier injection with an electric field applied between the first and second electrodes.

17. The optical device of claim 16, further comprising:

a third electrode electrically coupled to the light source region, the third electrode configured to modulate an electrical carrier concentration in the light source region by an electric field applied between (i) the first electrode and the third electrode or (ii) the second electrode and the third electrode.

18. The optical device of claim 17, wherein the light source region comprises at least two layers of different materials, and the first electrode and the third electrode are in physical contact with the layers of different materials of the light source region.

19. The optical apparatus of claim 17, wherein a dielectric layer is formed between the third electrode and the light source region, and the third electrode is configured to modulate an amount of electrical carriers recombined in the light source region by a capacitive effect without injecting the electrical carriers into the light source region.

20. An optical device as claimed in claim 17, wherein at least two different voltage levels are applied to the third electrode in sequence to modulate the amount of electrical carriers recombined in the light source region to obtain different output optical power levels.

21. The optical device of claim 17, wherein the grating region and the third electrode are located on opposite sides of the interference region, and the light is emitted through the grating region side.

22. The optical device of claim 17, wherein the grating region and the third electrode are located on opposite sides of the interference region, and the light is emitted through the opposite side of the grating region.

23. The optical device of claim 17, wherein the grating region and the third electrode are located on a same side of the interference region, and the light is emitted through the grating region side.

24. The optical device of claim 17, wherein the grating region and the third electrode are located on a same side of the interference region, and the light is emitted through an opposite side of the grating region.

25. The optical apparatus of claim 17 wherein at least a portion of the third electrode is transparent to light emitted through the side of the grating region.

26. A method for forming an optical transmitter, the method comprising:

forming a light source region;

forming an interference region, a first reflective region and a second reflective region, wherein the interference region in which the light source region is at least partially embedded is defined by the first and second reflective regions at two opposing ends along a first direction;

forming a grating region comprising a first grating structure covering at least a portion of the interference region, wherein a periodicity of the first grating structure substantially matches a period of the interfering light along a first direction; and

forming a quarter-wave shift region in the grating region by removing or adding at least one section of the grating structure,

wherein light generated by recombination of electrical carriers resonates within the interference region in the first direction and exits the interference region in a second direction different from the first direction.

27. The method of claim 26, wherein the grating region further comprises a second grating structure having the same periodicity as the first grating structure but a different duty cycle and a third grating structure that is a surface wave corrugated structure forming a DFB-type reflection region.

28. The method of claim 26, further comprising: forming a tapered region adjacent to the quarter-wavelength shift region along the first direction, wherein a period and a duty cycle of the tapered region increase or decrease from a side closer to the quarter-wavelength shift region toward a side away from the quarter-wavelength shift region.

29. The method of claim 26, further comprising: forming at least three electrodes electrically coupled to the light source region, wherein the three electrodes are arranged to provide control of relative electric fields between the three electrodes to modulate an electrical carrier concentration within the light source region, and one of the electrodes is an insulated electrode without electrical carrier injection.

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