Red-green-blue vertical cavity surface emitting laser array

Abstract

To provide a red-green-blue (RGB) vertical cavity surface emitting laser (VCSEL) array.SOLUTION: Each VCSEL in a VCSEL array has a diffraction grating, one or more active regions, and two distributed Bragg reflectors. Each VCSEL corresponds to either red, green, or blue wavelengths. The number of active regions in each VCSEL may be based on the color being emitted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is filed on December 16, 2022, and relates to a RED-GREEN-BLUE, VERTICAL-CAVITY, SURFACE-EMITTING LASER. This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 433,147, entitled "RED-GREEN-BLUE VERTICAL-CAVITY SURFACE-EMITTING LASER ARRAY," the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002]

[0002] The limitations and disadvantages of VCSEL arrays will become apparent to those skilled in the art through a comparison of such approaches with certain aspects of the present methods and systems discussed in the remainder of this disclosure with reference to the drawings. Summary of the Invention

[0003]

[0003] Provided are systems and methods for producing RGB VCSEL arrays, as more fully discussed in the claims, substantially as illustrated by and / or described with respect to at least one of the figures. [Brief explanation of the drawings]

[0004] [Figure 1]

[0004] FIG. 1 illustrates an example embodiment of the present disclosure, including a 2D RGB VCSEL array, according to various example implementations of the present disclosure. [Figure 2]

[0005] 1 illustrates an example embodiment of the present disclosure including an active region and a tunnel junction between distributed Bragg reflector (DBR) mirror stacks, according to various example implementations of the present disclosure. [Figure 3]

[0006] Figures 3a, 3b, and 3c illustrate an example embodiment of the present disclosure including an active region between DBR mirror stacks, according to various example implementations of the present disclosure, respectively. [Figure 4]

[0007] 4a and 4b are diagrams illustrating example embodiments of the present disclosure including an RGB VCSEL array for AR applications, according to various example implementations of the present disclosure. [Figure 5]

[0008] 1A-1C illustrate example embodiments of on-wafer micro-optics systems, according to various example implementations of the present disclosure. [Figure 6] 1A-1C illustrate example embodiments of on-wafer micro-optics systems, according to various example implementations of the present disclosure. [Figure 7]

[0009] Figures 7a, 7b, and 7c illustrate example embodiments of the present disclosure including a VCSEL without a lens, according to various exemplary implementations of the present disclosure, respectively. [Figure 8]

[0010] Figures 8a, 8b, and 8c illustrate example embodiments of the present disclosure including a VCSEL with a collimator, according to various example implementations of the present disclosure. [Figure 9]

[0011] Figures 9a, 9b, and 9c illustrate example embodiments of the present disclosure including a VCSEL with a diffuser, according to various exemplary implementations of the present disclosure, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0005]

[0012] The present disclosure describes a composite array of vertical cavity surface emitting lasers (VCSELs) that includes individual VCSELs that emit light at one wavelength of a group of three or more wavelengths, where each wavelength in the group of wavelengths is within the blue range (i.e., 440 to 495 nm), the green range (i.e., 495 to 580 nm), or the red range (i.e., 610 to 760 nm).

[0006]

[0013] FIG. 1 illustrates an example embodiment of the present disclosure, including a 2D RGB VCSEL array, according to various example implementations of the present disclosure.

[0014] As an example implementation, separate VCSELs are used in each wavelength range and integrated on a chip to form a 1D or 2D array. GaN-based VCSELs with InGaN active regions may be used with dielectric mirrors for the blue and green ranges. VCSELs with (AlGa)InP active regions and AlGaAs N and P distributed Bragg reflector (DBR) mirror stacks grown on GaAs substrates may be used for the red range.

[0007]

[0015] The arrays can be ordered 101 or unordered 103. The composite arrays can be addressable by row, by column, or at the individual VCSEL level. The arrays 101, 103 can be biased in a common cathode or common anode configuration.

[0008]

[0016] The arrays 101, 103 may have additional VCSEL attributes and process elements. For example, the VCSEL arrays 101, 103 may use a laser transfer process. Laser-Induced Forward Transfer (LIFT) and pixel / repair adjustment may be used to reduce the cost of building the RGB VCSEL arrays 101, 103.

[0009]

[0017] To overcome surface recombination on the chip sidewalls in micro-LEDs and micro-VCSELs, the chip contours are sometimes implanted from the top side through all epilayers remaining on the chip after laser transfer.

[0010]

[0018] Blue and green GaN-based VCSEL structures may include a dielectric DBR mirror. The light-generating section (active region) of the VCSEL may be grown by epitaxy. A wafer bonding process or wafer fusion bonding may be used to combine the DBR stack with the active region. Fusion bonding refers to the natural adhesion of two planar substrates without the addition of any intermediate layers. As an alternative approach, a properly designed DBR may be individually placed for each emitter at each wavelength using a two-step laser transfer process, with the first step being the DBR and the second step being for the active region. Because the dielectric DBR is an insulator, an intracavity contact is used to inject current into the active region.

[0011]

[0019] Pulsed laser deposition (PLD) is the deposition of reflective layers, sometimes used for resonant cavity LEDs. PLD involves depositing a thin film on the surface of a solid target inside a vacuum chamber. It is a thin film deposition technique that uses high-energy laser pulses to vaporize a material. The vapor is then solidified on a substrate to form a thin film up to a few micrometers in thickness. Thin films of reflective material can be used as mirrors in blue or green LEDs. While the reflectivity may not be high enough to use the mirror in a VCSEL structure, the mirror may be used in a resonant cavity (RC) LED. This may simplify and reduce the cost of blue and green light sources in some applications that utilize RC LEDs instead of VCSELs.

[0012]

[0020] FIG. 2 illustrates an example embodiment of the present disclosure including an active region 205 and a tunnel junction 207 between DBR mirror stacks 201 and 203 according to various example implementations of the present disclosure.

[0013]

[0021] This multi-junction VCSEL technology implements multiple active regions 205 and tunnel junctions 207 between the two DBR mirror stacks 201 and 203. This allows for a more efficient VCSEL, where multiple photons are emitted per electron. Adding additional active regions 205 and tunnel junctions 207 increases the power and slope efficiency, while also resulting in higher voltages.

[0014]

[0022] In the context of RGB VCSELs, the efficiency of blue lasers is typically lower due to material property constraints. Blue laser efficiency can be improved using this exemplary junction technique. Higher efficiency lasers (i.e., red) may use standard single junctions. This may allow the use of the same current supply with equivalent output power for the three RGB VCSELs.

[0015]

[0023] Lithographically defined apertures may provide an alternative to oxide apertures. Oxide-free VCSEL structures may use lithographically defined intracavity mesas for current and mode confinement. The confinement properties of such intracavity mesas are comparable to oxide apertures, with greater precision control of aperture size.

[0016]

[0024] In another variant, the aperture may be controlled by a combination of a tunnel junction and a p-n junction. The p-n junction may be reverse biased, thus blocking current flow. The VCSEL aperture may be determined by the lateral dimensions of the tunnel junction. With lithographic precision, the modal content of the device may be precisely controlled in the production flow. For example, AR applications may use narrow linewidths produced by such precise modal control.

[0017]

[0025] 3a-3c illustrate an example embodiment of the present disclosure including an active region 305 between DBR mirror stacks 303 and 307 according to various example implementations of the present disclosure. The optical properties of the layers in AR glasses may reach maximum efficiency for polarized light. To ensure single polarization for an RGB-emitting light source, a grating layer 301 may be defined in the cap layer on the light-emitting side. FIG. 3a shows how this solution may be used for a top-emitting device. FIG. 3b shows how this solution may be used for a bottom-emitting device. The grating 301 may be defined by lithography. The pitch and duty cycle may be optimized for maximum polarization extinction ratio.

[0018]

[0026] The solution in Figure 3c can be used for either top-emitting or bottom-emitting devices. Additionally, backside emitting VCSELs (eg, bottom emitting) with polarization locking and optics on the substrate are possible.

[0019]

[0027] Polarization locking can be achieved within the VCSEL cavity if additional optical functionality (e.g., a lens, diffuser, etc.) is added to the emitting side of the VCSEL. A grating layer 301 is then etched inside the cavity, as shown in Figure 3c. This structure can be realized by using wafer bonding or regrowth techniques.

[0020]

[0028] Open-Dirac electromagnetic cavities with linear dispersion may be realized by truncated photonic crystals arranged in a hexagonal pattern. Such open-Dirac electromagnetic cavities may exhibit unconventional scaling of losses in reciprocal space, leading to single-mode lasing that is sustained as the cavity is scaled in size. VCSELs may be developed based on the principles of open-Dirac electromagnetic cavities with linear dispersion. These VCSELs may be current-injected and may operate in the RGB range.

[0021]

[0029] 4a-4b illustrate example embodiments of the present disclosure, including an RGB VCSEL array for AR applications, according to various example implementations of the present disclosure. The ability to extend single-mode operation to larger apertures can be highly advantageous for AR applications.

[0022]

[0030] As shown in Figure 4a, the RGB projector 401 may be aimed at a reflective element 407 on the AR glasses 403 before being viewed 405. As shown in Figure 4b, the RGB projector 401 may also be aimed at a waveguide within the AR glasses 403 before being viewed 405.

[0023]

[0031] 5 and 6 illustrate exemplary embodiments of a micro-optics system on a wafer according to various exemplary implementations of the present disclosure. Micro-optics elements can be integrated on top of VCSEL emitters using a wafer-level process based on nanoimprint lithography (NIL) of a polymer layer dispensed above the VCSEL wafer. Using the NIL process, micro-optics elements with high conformal accuracy can be produced with a positional accuracy of <1 um. NIL technology offers the flexibility to produce a variety of microlenses with different designs, formats, and shapes.

[0024]

[0032] 7a-7c illustrate example embodiments of the present disclosure, including a VCSEL without a lens, according to various example implementations of the present disclosure. Fig. 7a shows the physical VCSEL. Fig. 7b shows the far field of this VCSEL without a lens. Fig. 7c shows that the far field of the VCSEL without a lens is approximately 30°.

[0025]

[0033] Two examples of micro-optical elements are collimators and diffusers. Figures 8a-8c illustrate example embodiments of the present disclosure, including a VCSEL with a collimator, according to various example implementations of the present disclosure. Figure 8a shows the physical VCSEL with the collimator. Figure 8b shows the far field of this VCSEL with the collimator. Figure 8c shows that this collimator can collimate the far field of the VCSEL to below 10° (from approximately 30° as shown in Figure 7c).

[0026]

[0034] 9a-9c illustrate example embodiments of the present disclosure, including a VCSEL with a diffuser, according to various example implementations of the present disclosure. Figure 9b shows a typical VCSEL. Figure 9b shows the far field of this VCSEL with a diffuser. Figure 9c shows that this diffuser can extend the far field of the VCSEL to over 65° (from approximately 30° as shown in Figure 7c).

[0027]

[0035] The method and / or system may be realized in hardware, software, or a combination of hardware and software. The method and / or system may be realized in a centralized fashion in at least one computing system, or in a distributed fashion where different elements are spread across several interconnected computing systems. Any kind of computing system or other apparatus adapted to perform the methods described herein is suitable. A typical implementation may include one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and / or one or more processors (e.g., x86, x64, ARM, PIC, and / or any other suitable processor architecture) and associated supporting circuitry (e.g., memory, DRAM, flash, bus interface circuits, etc.). Each separate ASIC, FPGA, processor, or other circuit may be referred to as a "chip," and multiple such circuits may be referred to as a "chipset." Another implementation may include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, or the like) having stored thereon one or more lines of code that, when executed by a machine, cause the machine to perform a process as described in this disclosure. Another implementation may include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, or the like) having stored thereon one or more lines of code that, when executed by a machine, cause the machine to be configured to operate as a system as described in this disclosure (e.g., loading software and / or firmware into the circuitry of the machine).

[0028]

[0036] As used herein, the terms "circuitry" and "circuitry" refer to physical electronic components (i.e., hardware) as well as any software and / or firmware ("code") that may comprise, be executed by, and / or otherwise be associated with the hardware. As used herein, for example, a separate processor and memory may comprise a first "circuit" when executing a first line or lines of code, and a second "circuit" when executing a second line or lines of code. As used herein, "and / or" means any one or more of the items in the list connected by "and / or." As an example, "x and / or y" means any element of the 3-element set {(x),(y),(x,y)}. As another example, "x, y, and / or z" means any element of the 7-element set {(x),(y),(z),(x,y),(x,z),(y,z),(x,y,z)}. As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the terms "for example" and "for example, but" precede the recitation of one or more non-limiting examples, instances, or illustrations. As used herein, circuitry is "operable" to perform a function whenever it includes the necessary hardware and code (if anything is needed) to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory adjustment, etc.). As used herein, the term "based on" means "based at least in part on." For example, but not limited to, "x based on y" means that "x" is based at least in part on "y" (and, for example, but not limited to, may be based on z).

[0029]

[0037] While the present methods and / or systems have been described with reference to certain implementations, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present methods and / or systems. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, it is not intended that the present methods and / or systems be limited to the particular implementations disclosed, but rather that the present methods and / or systems will include all implementations falling within the scope of the appended claims. [Explanation of symbols]

[0030] 101 array, VCSEL array, RGB VCSEL array 103 array, VCSEL array, RGB VCSEL array 201 DBR mirror stack 203 DBR mirror stack 205 Active area 207 Tunnel Junction 301 Diffraction Grating Layer, Diffraction Grating, Intra-Cavity Diffraction Grating 303 DBR mirror stack 305 Active region 307 DBR mirror stack 401 RGB Projector 403 AR Glasses 405 Being seen 407 Reflective Elements

Claims

1. Vertical Cavity Surface Emitting Laser (VCSEL) Array A system comprising: The array of VCSELs comprises: at least one VCSEL operable to emit light in the blue wavelength range; at least one VCSEL operable to emit light in the green wavelength range; at least one VCSEL operable to emit light in the red wavelength range; Including, Each VCSEL in the array of VCSELs has: an active region; Two distributed Bragg reflectors Including, system.

2. 10. The system of claim 1, wherein the blue wavelength range is 440 to 495 nm, the green wavelength range is 495 to 580 nm, and the blue wavelength range is 610 to 760 nm.

3. 10. The system of claim 1, wherein the array of VCSELs is a one-dimensional array.

4. 10. The system of claim 1, wherein the array of VCSELs is a two-dimensional array.

5. 10. The system of claim 1, wherein the at least one VCSEL operable to emit light in the blue wavelength range is GaN-based and includes an InGaN active region.

6. 10. The system of claim 1, wherein the at least one VCSEL operable to emit light in the green wavelength range is GaN-based and includes an InGaN active region.

7. 10. The system of claim 1, wherein the at least one VCSEL operable to emit light in the red wavelength range includes an (AlGa)InP active region and an AlGaAs N and P distributed Bragg reflector (DBR) mirror stack grown on a GaAs substrate.

8. 10. The system of claim 1, wherein at least one VCSEL in the array of VCSELs includes a plurality of active regions between the two DBR mirror stacks.

9. 9. The system of claim 8, wherein each active region of the plurality of active regions is separated from each other active region of the plurality of active regions by a tunnel junction.

10. 9. The system of claim 8, wherein the at least one VCSEL including the plurality of active regions between the two DBR mirror stacks is operable to emit light in the blue wavelength range.

11. 11. The system of claim 10, wherein the at least one VCSEL operable to emit light in the red wavelength range has a single active layer between the two DBR mirror stacks. system, including the sexual domain.

12. 12. The system of claim 11, wherein the at least one VCSEL operable to emit light in the blue wavelength range and the at least one VCSEL operable to emit light in the red wavelength range are operably powered by a common current supply.

13. 10. The system of claim 1, wherein each VCSEL of the array of VCSELs includes a diffraction grating in a cap layer on a light-emitting side.

14. 10. The system of claim 1, wherein each VCSEL in the array of VCSELs includes a diffraction grating adjacent to an active region.

15. 15. The system of claim 14, wherein the diffraction grating is etched inside a cavity.

16. 10. The system of claim 1, wherein each VCSEL of the array of VCSELs comprises an open Dirac electromagnetic cavity with linear dispersion.

17. 10. The system of claim 1, wherein each VCSEL in the array of VCSELs includes a microlens.

18. 20. The system of claim 17, wherein the microlens is a collimator.

19. 20. The system of claim 17, wherein the microlens is a diffuser.

20. 18. The system of claim 17, wherein the microlenses are integrated on top of each VCSEL by nanoimprint lithography (NIL) of a polymer layer.

Images