Coupling of vcsel / pcsel light to multilayer waveguide for short-range optical communication

Abstract

To describe an optical communication system for coupling light into a multilayer waveguide via a VCSEL or PCSEL.SOLUTION: An optical communication system includes a plurality of emitters, a semi-insulating (SI) substrate, a plurality of electrical contacts, a plurality of waveguides, and a diffractive optical coupling system. The SI substrate supports the plurality of emitters. The plurality of electrical contacts is configured to individually adjust each emitter. The plurality of waveguides and the plurality of emitters are separated by an air gap. The diffractive light coupling system is configured to direct light emitted from the plurality of emitters into the waveguide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 574,118, entitled "VCSEL / PCSEL LIGHT COUPLING INTO THE MUTILAYER WAVEGUIDE FOR SHORT REACH OPTICAL COMMUNICATION," filed April 3, 2024, which is hereby incorporated by reference in its entirety. [Background technology]

[0002]

[0002] The limitations and disadvantages of conventional systems and methods for optical coupling will become apparent to those skilled in the art through a comparison of those approaches with certain aspects of the present methods and systems described in the remainder of this disclosure with reference to the drawings. Summary of the Invention

[0003]

[0003] As more fully described in the claims, there is provided a system and method for coupling VCSEL / PCSEL light into a multilayer waveguide for short-distance optical communication, as substantially illustrated by and / or substantially described in connection with at least one of the figures. [Brief explanation of the drawings]

[0004] [Figure 1]

[0004] FIG. 1 illustrates a first exemplary side view of a bottom-emitting VCSEL / PCSEL in accordance with various exemplary implementations of the present disclosure. [Figure 2]

[0005] FIG. 10 illustrates a second exemplary side view of a bottom-emitting VCSEL / PCSEL in accordance with various exemplary implementations of the present disclosure. [Figure 3]

[0006] FIG. 10 illustrates a third exemplary side view of a bottom-emitting VCSEL / PCSEL in accordance with various exemplary implementations of the present disclosure. [Figure 4]

[0007] 1A-1C illustrate example top views of bottom-emitting VCSELs / PCSELs according to various example implementations of the present disclosure. [Figure 5]

[0008] FIG. 2 illustrates a first exemplary side view of a transmitter and a receiver according to various exemplary implementations of the present disclosure. [Figure 6]

[0009] FIG. 10 illustrates a second exemplary side view of a transmitter and receiver according to various exemplary implementations of the present disclosure. [Figure 7]

[0010] FIG. 1 illustrates an example side view of a PD / TIA array receiver, in accordance with various example implementations of the present disclosure. [Figure 8]

[0011] 1A-1C illustrate an example waveguide interposer coupled to a transmitter and a receiver, in accordance with various example implementations of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0005]

[0013] The present disclosure relates to laser-based optical communication systems that utilize arrays of lasers for data transmission over waveguides. The following discussion provides various example lasers, such as vertical-cavity surface-emitting lasers (VCSELs) or photonic crystal surface-emitting lasers (PCSELs). Such examples are not limiting, and the scope of the appended claims should not be limited to the particular examples disclosed. In the following discussion, the terms "example" and "for example" are not limiting.

[0006]

[0014] The figures show the general style of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. Additionally, elements in the figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the examples discussed in this disclosure. The same reference numerals in different figures represent the same elements.

[0007]

[0015] The terms "comprises," "comprising," "includes," and / or "including" are "open-ended" terms that specify the presence of stated features but do not exclude the presence or addition of one or more other features.

[0008]

[0016] Terms such as "first," "second," and the like may be used herein to describe various elements, and these elements should not be limited by these terms. These terms are used only to distinguish one element from another. Thus, for example, a first element discussed in this disclosure could be termed a second element without departing from the teachings of the disclosure.

[0009]

[0017] Unless otherwise specified, the term "coupled" may be used to describe two elements in direct contact with each other, or to describe two elements that are indirectly connected by one or more other elements. For example, if element A is coupled to element B, element A may be in direct contact with element B, or may be indirectly connected to element B by an intervening element C. Similarly, the terms "over" or "on" may be used to describe two elements in direct contact with each other, or to describe two elements that are indirectly connected by one or more other elements.

[0010]

[0018] Current optical communication technologies face challenges in compactly integrating and efficiently coupling vertically emitting sources into waveguides arranged on multiple levels. The present disclosure addresses these challenges by providing a novel assembly design that integrates an array of individually tuned emitters with waveguides to enable efficient data communication. The disclosed assembly minimizes emitter pitch through the use of a shared semi-insulating (SI) substrate and current spreading layer. Light from each individually tuned emitter is launched separately into either a channel or a planar waveguide, which can be horizontally distributed within a single layer and / or stacked vertically.

[0011]

[0019] 1-3 show example side views of bottom-emitting vertical cavity surface-emitting laser (VCSEL) or photonic crystal surface-emitting laser (PCSEL) configurations. FIG. 4 provides a top view of such an example implementation. FIG. 5 and FIG. 6 show example side views of transmitter and receiver configurations according to various example implementations of the present disclosure.

[0012]

[0020] The assembly includes multiple backside emitters (BEs) 101, electrical contacts (n 103 and p1 105, p2 105, p3 105), and a semi-insulating (SI) substrate 107. The multiple BEs 101 may be arranged as an array of VCSELs or PCSELs. Each emitter 101 in the array can be individually tuned via a separate electrical contact (p1 105, p2 105, p3 105). The emitters 101 can share a common current spreading layer 109 and n-type electrical contact 103, which reduces the emitter-to-emitter pitch. The polarity of the electrical contacts can be set according to the driver 111 and epitaxial design.

[0013]

[0021] Multiple BEs 101 can include emitters with the same or different wavelengths. For the SI substrate 107, the wavelength can be 940 nm or greater to ensure optical transparency. Alternative substrate materials may be used to support a wider range of wavelengths.

[0014]

[0022] Polarization control of the emitted light may be achieved using a diffraction grating located at the device output or within the device structure. The active laser region from which the light emanates may be located above or below the current spreading layer. The driver 111 may be flip-chip bonded on top of the emitter array 101 or located adjacent to it. While the examples focus on bottom-emitting configurations, top-emitting variations may be implemented as well.

[0015]

[0023] The waveguides 115 may be directly integrated with the emitter devices, separated by a spacer containing index-matching material, or set across an air gap. Coupling of light into the waveguides 115 may be facilitated through a grating coupler 113 (shown in FIGS. 1, 2, and 5) embedded in the waveguide layer 115 or an etched mirror 301 (shown in FIG. 3). Prisms or gratings may be integrated onto the emitter array substrate surface 107 (shown in FIGS. 1-3) to redirect the beam towards the vertical rectangular grating coupler 113 for optimal waveguide coupling.

[0016]

[0024] As shown in Figure 2, the grating coupler 113 can be implemented as a second-order grating with a blazed profile. Effective index binary profile blazing or other optimized configurations can improve coupling efficiency. The grating period can be spatially tuned (i.e., chirped) to compensate for varying incidence angles due to beam divergence, ensuring efficient coupling into the waveguide layer.

[0017]

[0025] After passing through the grating coupler 113 (FIGS. 1, 2, and 5) or after being reflected by mirror 301 (FIG. 3), the light beam is tapered and can be directed into a channel waveguide that can connect to a wavelength multiplexer or can be routed to another waveguide section. The waveguides can include adiabatic tapers configured to control beam expansion and decoupling. The beam can further propagate in a plate-like waveguide.

[0018]

[0026] Focusing or collimating functions can be incorporated using diffractive, refractive, and / or Fresnel lenses. Diffractive optical couplers can utilize chirp periods or curved profiles to optimize coupling efficiency and divergence management. Such functions can be integrated into the bottom surface of the emitter array or within the diffraction grating coupler 113. Anti-reflective coatings may be applied to optical elements to reduce reflections back to the light source.

[0019]

[0027] Silicon nitride (SiN) may be used as the waveguide material, while silicon dioxide (SiO2) may serve as the cladding layer 117 to achieve sufficient refractive index contrast for effective mode confinement. Multilayered waveguides 115 may also be utilized with intervening cladding layers 117. Multiple waveguides 115 may be configured in a symmetric receiver-side design.

[0020]

[0028] As shown in Figure 5, the channel waveguides are placed in a coupling region where an adiabatic taper can be used for beam expansion and decoupling. A symmetric receiver-side design can be implemented that employs a decoupler to extract light from the waveguide. The size of the decoupling region can be optimized to achieve collimation of the extracted light while being constrained by the diffraction limit of the operating wavelength and the aperture size.

[0021]

[0029] When multiple input wavelengths are used, they may co-propagate within the channel or slab waveguide, and the grating coupler may be designed to selectively couple or decouple specific wavelengths without affecting the propagation of wavelengths other than the specific wavelength within the waveguide.

[0022]

[0030] In addition to silicon nitride, other suitable waveguide materials include silicon oxycarbide (SiOC), aluminum nitride (AlN), aluminum oxynitride (AlON), amorphous silicon (a-Si), polysilicon, lithium niobate (LiNbO), and gallium nitride (GaN), which have refractive indices up to 2.3. A key requirement for the waveguide material is high refractive index contrast while maintaining compatibility with the glass substrate 119 through an appropriate cladding layer 117.

[0023]

[0031] Each emitter 101 may be individually addressable by a driver 111 via an associated P-contact 105 (P1, P2, P3, etc.). Typically, the N-contact 103 is shared while the P-contacts 105 are individually driven; however, this configuration may be reversed. The driver 111 may allow for a pitch density of less than one millimeter. The grating coupler 113, mirror 301, and other waveguide features may be fabricated using lithography to ensure precise alignment through lithographic mask design. Alignment to the substrate 107 and emitter 101 may be achieved via fiducial alignment marks. Compatibility with the glass plate 119 may be achieved through optimized placement and patterning. The fabricated mirror 301 may include a rotating mirror (e.g., a 45° or 90° reflector) or a metamaterial.

[0024]

[0032] Thermal constraints are primarily due to heat dissipation through the driver 111 and substrate 107. Current densities in data communications applications are not excessively high, but an additional heat spreading layer may be introduced beneath the silicon substrate if necessary. Electrical constraints are determined by the minimum pitch supported by the driver and interconnects, with copper pillars or other bonding techniques imposing a lower limit on emitter spacing.

[0025]

[0033] Optical loss at the waveguide coupling point is minimized through inverse design techniques that optimize the topology and geometry of the coupling structure. Loss can be mitigated by designing each of the mirror 301, diffraction grating 113, and metamaterial for reduced optical loss. A transimpedance amplifier (TIA) can be integrated with the photodetector 501 at the receiving end.

[0026]

[0034] The divergence angle can have a strong impact on the coupling efficiency. Exemplary divergence angles can be associated with numerical aperture (NA) values ​​between 0.14 and 0.25. A smaller divergence angle within the waveguide material can allow for tighter emitter spacing without beam overlap. Additional lens-like or focusing optical elements can be integrated in the substrate or within the grating coupler / metasurface.

[0027]

[0035] 6, the system may be coupled to an optical fiber network 601 via a grating coupler 113. The system may further be integrated with a photonic integrated circuit (PIC) where the glass plate 119 serves as the photonic platform. Wavelength division multiplexing (WDM) may be utilized to couple multiple emitters 101 to a single waveguide 115 and / or fiber 601.

[0028]

[0036] Bottom-emitting designs allow for efficient spatial integration by placing electrical contacts directly underneath the emitters, thereby enabling tighter emitter densities. In contrast, top-emitting designs require lateral contact placement, thereby resulting in lower emitter densities. High-density emitter arrays can be achieved with pitches as small as 10 microns, thereby enabling compact and efficient optical communication systems.

[0029]

[0037] FIG. 7 illustrates an example side view of a PD / TIA array receiver according to various example implementations of the present disclosure.

[0038] The assembly includes multiple photodetectors (PDs) 701, electrical contacts (n 703 and p1 705, p2 705, p3 705), and a semi-insulating (SI) substrate 707. The multiple PDs 701 may be arranged in an array. Each PD 701 in the array may be individually coupled to a separate electrical contact (p1 705, p2 705, or p3 705). The PDs 701 may share a common current spreading layer 709 and n-type electrical contact 703, which reduces the inter-detector pitch. The polarity of the electrical contacts may be set according to the driver 111 and epitaxial design.

[0030]

[0039] The PDs 701 may be identical or differentiated by wavelength. For the SI substrate 707, the wavelength may be 940 nm or greater to ensure optical transparency. Alternative substrate materials may be used to support a wider range of wavelengths.

[0031]

[0040] Polarization of the received light may be achieved using a diffraction grating located at the device input or within the device structure. The light receiving region may be located above or below the current spreading layer. The TIA array architecture 711 may be flip-chip bonded on top of or adjacent to the PD array 701. While the examples focus on a bottom-emitting configuration, top-emitting variations may be implemented as well.

[0032]

[0041] The waveguides 715 may be directly integrated with the emitter devices, separated by a spacer containing a refractive index-matching material, or set across an air gap. Coupling of light into the waveguides 715 can be facilitated through a grating coupler 713 (similar to those shown in FIGS. 1, 2, and 5) or an etched mirror (similar to that shown in FIG. 3) embedded in the waveguide layer 715. A prism or grating may be integrated onto the substrate surface 707 of the PD array 701 to redirect the beam toward the vertical rectangular grating coupler 713 for optimal waveguide coupling.

[0033]

[0042] 8 illustrates an example waveguide interposer coupled to a transmitter and a receiver according to various exemplary implementations of the present disclosure. Figure 8 illustrates that the VCSEL / driver array (of FIGS. 1-3) and the PD / TIA array (of FIG. 7) can be disposed on a common waveguide interposer comprising multiple waveguides 115, multiple cladding layers 117, and a glass plate 119.

[0034]

[0043] As used herein, the terms “circuit” 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 hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first one or more lines of code, and a second “circuit” when executing a second one or more lines of code. As used herein, “and / or” means any one or more of the items in the list linked by “and / or.” As one example, “x and / or y” means any element of the ternary set {(x), (y), (x, y)}. As another example, “x, y, and / or z” means any element of the septenary 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 "eg" and "for example" begin a recitation of one or more non-limiting examples, instances, or illustrations. As used herein, a circuit is "operable" to perform a function whenever it comprises the necessary hardware and (if necessary) code to perform the function, regardless of whether performance of the function is disabled or enabled (e.g., by a user-configurable setting, factory setup, etc.). As used herein, the term "based on" means "based at least in part on." For example, "x based on y" means that "x" is at least in part based on "y" (and may further be based on, e.g., z).

[0035]

[0044] Although the present methods and / or systems have been described with reference to certain specific implementations, those skilled in the art will recognize that various modifications may be made and equivalents may be substituted without departing from the scope of the present methods and / or systems. Additionally, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its scope. 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.

Claims

1. A substrate; a plurality of backside emitters (BE) disposed on the substrate; a current spreading layer shared by the plurality of BEs; a plurality of individually addressable electrical contacts configured to separately adjust each BE of the plurality of BEs; a plurality of waveguides configured to receive light emitted by the plurality of beam emitters; one or more coupling elements configured to direct light from the plurality of BEs into the plurality of waveguides; 1. An optical communication assembly comprising:

2. The optical communications assembly of claim 1 , wherein the one or more coupling elements include at least one of a grating coupler and an etched mirror.

3. 10. The optical communication assembly of claim 1, wherein each of the plurality of waveguides is made of silicon nitride (SiN) and silicon dioxide (SiO ２ and a cladding layer of said optical fiber.

4. The optical communication assembly of claim 1 , wherein anti-reflective features are integrated into the one or more coupling elements.

5. 10. The optical communications assembly of claim 1, wherein the plurality of BEs include at least one of vertical cavity surface emitting lasers (VCSELs) and photonic crystal surface emitting lasers (PCSELs).

6. 10. The optical communication assembly of claim 1, wherein the plurality of waveguides are arranged as one of a single horizontal layer and multiple vertically stacked layers.

7. 10. The optical communications assembly of claim 1, wherein the emitted light is redirected towards the vertical rectangular grating coupler via one of a prism and a diffraction grating.

8. 10. The optical communication assembly of claim 1, the optical communication assembly includes a second-order diffraction grating; the second-order grating includes one of a blazed profile and a plurality of chirped grating periods. Optical communication assembly.

9. 10. The optical communication assembly of claim 1, wherein the plurality of waveguides comprises at least one of a channel waveguide and a planar waveguide.

10. 10. The optical communication assembly of claim 1, wherein the plurality of waveguides provide wavelength multiplexing.

11. a plurality of emitters; a semi-insulating (SI) substrate supporting the plurality of emitters; a plurality of electrical contacts configured to individually adjust each emitter of the plurality of emitters; a plurality of waveguides, the plurality of waveguides and the plurality of emitters being separated by air gaps; a diffractive optical coupling system configured to direct light emitted from the plurality of emitters into the waveguide; and An optical waveguide system comprising:

12. 12. The system of claim 11, wherein the plurality of emitters comprises at least one of a vertical cavity surface emitting laser (VCSEL) and a photonic crystal surface emitting laser (PCSEL).

13. 12. The system of claim 11, wherein the diffractive optical coupling system comprises a chirped diffraction grating.

14. 12. The system of claim 11, wherein the plurality of waveguides comprises waveguides stacked with intervening cladding layers.

15. 12. The system of claim 11, wherein the plurality of waveguides are configured to guide light to an optical multiplexer for wavelength division multiplexing.

16. 12. The system of claim 11, wherein the diffractive light coupling system includes a Fresnel lens configured to collimate the emitted beam.

17. 12. The system of claim 11, wherein the plurality of waveguides are configured in a symmetric receiver-side design.

18. 12. The system of claim 11, wherein at least one waveguide of the plurality of waveguides is configured to allow multiple wavelengths to co-propagate.

19. 12. The system of claim 11, wherein a diffraction grating for the plurality of emitters is configured to control the polarization of the emitted light.

20. 12. The system of claim 11, wherein the plurality of waveguides include an adiabatic taper configured to control beam expansion and decoupling.

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