Silicon-assisted packaging of high-power integrated semiconductor optical amplifier arrays

Abstract

To solve the problems in which conventional LiDAR systems use mechanical moving components and bulk optical lens elements to steer a laser beam and thus are too bulky, costly, and unreliable.SOLUTION: A light detection and ranging (LiDAR) system for a vehicle comprises a semiconductor optical amplifier (SOA) chip. The SOA chip comprises: at least one first SOA emitting amplified light passing through the SOA chip in a first direction; at least one second SOA emitting amplified light passing through the SOA chip in a second direction; and a particular chip facet, where an optical input of the SOA chip and optical outputs of the SOAs are positioned on the particular chip facet. The at least one first SOA and the at least one second SOA are configured to provide different amounts of amplification.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority under 35 U.S.C § 119(e) to U.S. Provisional Patent Application No. 62 / 960,688, filed on January 13, 2020, the entire contents of which are hereby incorporated by reference in their entirety.

[0002] The content of the present disclosure generally relates to Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR), and more specifically, to a solid - state FMCW LiDAR system.

Background Art

[0003] Conventional LiDAR systems use mechanical moving parts and bulk optical lens elements (i.e., refractive lens systems) to steer laser beams. And for many applications (e.g., automobiles), they are too bulky, expensive, and unreliable.

Summary of the Invention

[0004] A photonic integrated circuit (PIC) assembly includes a semiconductor optical amplifier (SOA) and a U-turn chip. The input SOA and multiple SOA are arranged parallel to each other. The U-turn chip includes an optical splitter and a waveguide assembly. The optical splitter is configured to receive amplified input light propagating from the input SOA in a first direction and to split the amplified light into multiple beams. The waveguide assembly is configured to guide each of the multiple beams to the corresponding SOA of the multiple SOA. The waveguide assembly also adjusts the propagation direction of each guided beam to be substantially parallel to a second direction that is substantially opposite to the first direction. Each of the multiple SOA is configured to amplify its own beam to produce multiple amplified output beams. A PIC assembly may, for example, be part of a frequency-modulated continuous wave (FMCW) LiDAR system.

[0005] In some embodiments, the PIC assembly includes a semiconductor optical amplifier (SOA) module. The SOA module includes an SOA array and may further include a U-turn chip (in alternative embodiments, the U-turn chip may be part of the PIC chip to which the SOA module is coupled). The SOA array is located on the SOA chip. The SOA array includes an input SOA and a plurality of SOA, which are arranged parallel to each other. The U-turn chip is coupled to the SOA chip and includes an optical splitter and a waveguide assembly. The optical splitter is configured to receive amplified input light propagating from the input SOA in a first direction and to split the amplified light into a plurality of beams. The waveguide assembly is configured to guide each of the plurality of beams to the corresponding SOA of the plurality of SOA, and the waveguide assembly adjusts the propagation direction of each guided beam to be substantially parallel to a second direction substantially opposite to the first direction, and each of the plurality of SOA is configured to amplified its respective beam to produce a plurality of amplified output beams. [Brief explanation of the drawing]

[0006] Other advantages and features of the embodiments of this disclosure will become more readily apparent from the following detailed description relating to the examples in the accompanying drawings and from the accompanying claims.

[0007] [Figure 1] A top-down view of an optical integrated circuit assembly including two SOA array chips and two corresponding U-turn chips coupled to a PIC chip according to one or more embodiments is shown.

[0008] [Figure 2] A cross-section of one embodiment of an SOA array module according to one or more embodiments is shown.

[0009] [Figure 3] Another embodiment of a cross-section of an SOA array module coupled to a PIC chip is shown.

[0010] [Figure 4a] An exemplary manufacturing process according to one or more embodiments will be described. [Figure 4b] An exemplary manufacturing process according to one or more embodiments will be described.

[0011] [Figure 5a] This document describes a PIC assembly including a suspended U-turn chip according to one or more embodiments. [Figure 5b] This document describes a PIC assembly including a suspended U-turn chip according to one or more embodiments.

[0012] [Figure 6] This document describes a PIC assembly that includes a suspended U-turn chip and multiple comb drives according to one or more embodiments.

[0013] [Figure 7] This shows a top-down view of a PIC assembly including an external cavity laser according to one or more embodiments. [Modes for carrying out the invention]

[0014] An SOA module includes an SOA array (on an SOA array chip) and may include a U-turn chip (in other embodiments, the U-turn chip is part of a PIC circuit that the SOA module couples with). The SOA module may be coupled to a Photonic Integrated Circuit (PIC) chip. An SOA array includes an input SOA and a plurality of SOA. In some embodiments, the input SOA is the same as one or more of the plurality of SOA. In alternative embodiments, the input SOA and the plurality of SOA may be different (e.g., having different amplification levels). In some embodiments, each of the plurality of SOA is configured to provide the same amplification level. In other embodiments, at least one of the plurality of SOA provides a different amplification level from the input SOA and / or the other SOA. The input SOA and the plurality of SOA may be arranged in parallel to each other. PIC chips, U-turn chips, or combinations thereof can consist of silicon, silicon nitride, silicon dioxide, or combinations thereof, whereas SOA array chips can be manufactured from III-V compound semiconductor materials consisting of Al, Ga, In, N, P, As, and other elements.

[0015] The U-turn tip includes an optical splitter and a waveguide assembly. The optical splitter is configured to receive amplified input light propagating in a first direction from the input SOA and to split the amplified light into multiple beams. The waveguide assembly guides each of the multiple beams to the corresponding SOA of the multiple SOAs. The waveguide assembly also adjusts the propagation direction of each guided beam so that it is substantially parallel to a second direction which is substantially opposite to the first direction. In this manner, the light guided by the waveguide assembly performs another "U-turn" toward the SOA array.

[0016] Each of the multiple SOAs is configured to amplified its own beam to produce multiple amplified output beams. Since the SOA module may be part of an optical integrated circuit (PIC) assembly, the amplified output beams may be supplied to the PIC assembly for use, for example, in a frequency-modulated continuous wave (FMCW) LiDAR system. FMCW LiDAR directly measures the distance and velocity of an object by directing a frequency-modulated collimated light beam at the object. Light reflected from the object is combined with a tapped version of the beam. The frequency of the resulting beat tone is proportional to the distance from the LiDAR system to the object, corrected by a Doppler shift requiring a second measurement. The two measurements, which may or may not be performed simultaneously, provide both distance and velocity information.

[0017] It should be noted that a PIC assembly may include multiple SOA modules, light sources, and waveguides to provide light from a light source to multiple SOA modules. The waveguides can also be arranged to provide a similar U-turn function. This, combined with a parallel arrangement of SOA and U-turn chips, facilitates the simple integration and packaging of SOA modules and PIC chips. On the other hand, typical high-power SOA arrays have optical inputs and outputs on opposite sides of the III-V chip. This can make packaging SOAs with other photonics chips expensive and difficult.

[0018] Figure 1 shows a top-down view of an optical integrated circuit (PIC) assembly 100, which includes two SOA array chips 110 (also called SOA chips) and two corresponding U-turn chips 113 coupled to a PIC chip 102 by one or more embodiments. The PIC chip 102, the SOA array chips 110, the U-turn chips 113, or any combination of parts thereof, may consist of silicon, silicon nitride, silicon dioxide, or any combination of parts thereof.

[0019] The output optical power of the integrated laser source 101 is located on top of the PIC chip 102. The light from this source is coupled to a waveguide 103 that is patterned on the PIC chip 102.

[0020] The optical power in the waveguide is evenly split into two output waveguides 105 and 106 by the optical splitter 104. The optical splitter 104 can be, for example, a beam splitter. In this example, two SOA modules (i.e., 107, 108) are described, but in other embodiments, a different number of SOA modules can be used. Each of the SOA modules 107, 108 includes an SOA array chip 110 (also referred to as an SOA chip) and a U-turn chip 113 disposed within a recessed cavity etched on the upper surface of the PIC 102.

[0021] As shown, the output waveguide 105 is configured to provide a first beam to the SOA module 107 (and specifically the corresponding SOA array), and the output waveguide 106 is configured to provide a second beam to the SOA module 108 (and specifically the corresponding SOA array). Note that as shown, the propagation direction of light at the inlets of the output waveguide 105 and the output waveguide 106 is substantially opposite to the propagation direction at the outputs of the output waveguide 105 and the output waveguide 106.

[0022] Each SOA array chip includes an SOA array. The SOA array includes an input SOA (e.g., input SOA 111) and a plurality of SOAs (e.g., SOA 116). As shown, the input SOA and the plurality of SOAs are arranged parallel to each other. In other embodiments, the input SOA and the plurality of SOAs may be positioned relative to each other in a different manner.

[0023] In the context of the SOA module 107, the output waveguide 105 is edge-coupled to the SOA array chip 110 via a front chip facet 109.

[0024] This light passes through the input SOA 111 that functions as a pre-amplifier to offset losses associated with chip-to-chip coupling. The amplified light propagates in the first direction.

[0025] The pre-amplified light exits the SOA via the back facet 112 of the SOA tip 110, which is edge-coupled to the U-turn tip 113.

[0026] Light in the input waveguide passes through a 1×M splitter 114 (where M is the same as 1 minus the total number of SOAs in the SOA array 110, including the input SOA) which equally distributes the pre-amplified optical power among the M waveguides (e.g., waveguide 115) of the waveguide assembly. Each waveguide in the waveguide assembly contains a guided beam corresponding to a portion of the pre-amplified optical power.

[0027] The waveguide assembly adjusts the propagation direction of each guided beam to be substantially parallel to a second direction that is substantially opposite to a first direction. For example, the waveguide bends, and the light is recoupled to the SOA array chip 110 via the rear facet 112. Each optical channel passes through individual SOA 116 on the SOA array chip, amplifying the light to a desired output level (i.e., each of the multiple SOA is configured to amplify its respective beam to produce multiple amplified output beams). In some embodiments, each SOA 116 in the SOA array chip is configured to provide the same amplification level. In other embodiments, at least two of the SOA 116 have different amplification levels. Similarly, in some embodiments, multiple SOA modules on the PIC chip 102 are identical. And in other embodiments, at least one SOA module on the PIC chip 102 is different from the other SOA modules on the PIC chip 102. For example, one SOA module may have a different number of SOA than the other SOA modules.

[0028] The amplified light is edge-coupled again to the PIC chip 102 via the front chip facet 109 and to the waveguide 117. The light from the output waveguide 106 to the SOA module 108 is amplified within the SOA module 108 in substantially the same manner as described above for the SOA module 107, and output to the waveguide 118. Waveguides 117 and 118 within the PIC chip 102 carry light from the packaged SOA array to the optical circuits contained within the PIC chip 102.

[0029] Figure 2 shows a cross-section of one embodiment of an SOA array module 200 (also called an SOA module) coupled to a PIC chip 205 by one or more embodiments. The SOA array chip 201 is bonded to a carrier 203 that provides structural support and thermal management. The carrier 203 can be manufactured from silicon, other thermally conductive ceramics such as AlN or Al2O3, or a combination of some of these. The SOA array chip 201 may be one embodiment of an SOA array chip 110.

[0030] The U-turn chip 202 is actively bonded to the SOA array chip 201 with the help of a shim 204 that provides the necessary mechanical offset relative to the carrier 203. While it is advantageous to use a material with a similar coefficient of thermal expansion to the SOA 201 for the shim 204, it can be manufactured from any material because the alignment between the SOA 201 and the U-turn 202 is better preserved against temperature swings. The U-turn chip 202 is one embodiment of the U-turn chip 113. The U-turn chip 202 is thinned so that the combined module fits into a recess etched into the PIC chip 205. Such an array of the bonded SOA array chip 201, carrier 203, shim 204, and U-turn chip 202 forms the SOA array module 200.

[0031] The SOA array module 200 is positioned on a PIC chip 205 that utilizes the optical power provided by the SOA array chip 201. The PIC chip 205 includes a patterned base 206 that provides mechanical support, precise out-of-plane alignment, and means for securing the SOA array chip 201 to the PIC chip 205. The SOA array module is positioned on top of these bases 206, and its front facets are mounted close to the chip facets 207 and actively aligned to provide efficient optical coupling between the SOA array chip 201 and the PIC chip 205. Note that in the illustrated embodiment, the U-turn chip 202 is on the opposite side of the SOA array chip 201 from the chip facets 207. In other embodiments, the position of the chip facets 207 relative to the U-turn chip 202 may vary.

[0032] If necessary for additional support, the U-turn tip 202 may be bonded to a silicon optical tip having a low-shrinkage adhesive 208.

[0033] Figure 3 shows another embodiment of a cross-section of the SOA array module 300 coupled to the PIC chip 304. The SOA array module 300 simplifies the chip assembly process and reduces costs for mass production.

[0034] In this embodiment, the PIC chip 304 and the U-turn chip 302 are fabricated on the same wafer, and the waveguide 310 in the PIC 304 and the waveguide 311 in the U-turn chip 302 are self-aligned vertically. That is, they are at the same depth below the chip surface (e.g., aligned in the same plane). Also, the patterned base in the PIC chip 304 (e.g., base 305) and the patterned base in the U-turn chip 302 (e.g., base 303) are formed so that when the SOA chip 301 is positioned on these bases, the waveguide 309 in the SOA chip 301 aligns vertically with the waveguides 310 and 311. Precise vertical alignment in the chip assembly process affects performance, and the mechanical constraints provided by the self-aligning waveguides 309, 310, and 311 and the properly formed bases can significantly improve the yield and quality of the final chip assembly, potentially leading to higher throughput and lower manufacturing costs.

[0035] Figures 4a and 4b illustrate exemplary manufacturing processes according to one or more embodiments. The processes shown in Figures 4a and 4b may be performed by components of a circuit manufacturing system. Other entities may perform some or all of the steps of other embodiments of Figures 4a and 4b. Embodiments may include different and / or additional steps, or the steps may be performed in a different order.

[0036] As shown in Figure 4a, the PIC 404 and U-turn 402 are formed on the same wafer. The wafer can be manufactured from silicon, silicon nitride, silicon dioxide, several other suitable materials, or a combination of some of these. Waveguides 410 and 411 are at the same depth below the wafer surface. Similarly, the pedestals 405 and 403 are formed such that the top of pedestal 405 and the top of pedestal 403 are at the same depth below the wafer surface. Note that in the illustrated embodiment there are four pedestals 405 and two pedestals 403. In other embodiments there may be more or fewer pedestals 405 and / or more or fewer pedestals 403.

[0037] Figure 4b shows how the SOA module 400, which includes the SOA array chip 401 and the U-turn chip 402, is assembled. The U-turn chip 402 can be cut and thinned from the wafer shown in Figure 4a.

[0038] The SOA array tip 401 is bonded to a carrier 406, which may be an embodiment of the carrier 203. The U-turn tip 402 is then inverted, aligned, and bonded to the SOA array tip 401 together with a base 403 that touches the upper surface of the SOA array tip 401, providing vertical mechanical constraint. Primary bonding is provided by adhesive 408 (e.g., solder or glue) around the base 403, and secondary bonding may be added between the U-turn tip 402 and the carrier 406 using low shrinkage glue 408' along with shims 407 as needed for better mechanical stability. Because the height of the base 403 is precisely controlled, this method allows for manual alignment between the SOA array tip 401 and the U-turn tip 402.

[0039] Next, the SOA module 400 is inverted and bonded to the PIC chip 404. For example, as shown in Figure 3, the SOA module 400 is inverted and aligned with the waveguide 310 of the PIC 304 and bonded by adhesive 308 in a recessed cavity that accommodates the base (e.g., base 305) of the PIC chip 304 as a mechanical stop to ensure the vertical alignment of the assembly.

[0040] Figures 5a and 5b illustrate a PIC assembly 500 including a suspended U-turn chip 502 according to one or more embodiments. The PIC assembly 500 includes a PIC chip 505 connected to the suspended U-turn chip 500, and an SOA module. The SOA module includes an SOA array chip 501 and a carrier 503. Figure 5a is a cross-sectional view of the PIC assembly 500, and Figure 5b is a top-down view of the PIC assembly 500. The PIC chip 505 and the U-turn chip 502 are fabricated on the same wafer (for example, as in the embodiments described above in relation to Figure 4a). If the bottom of the U-turn chip 502 is hollow as a cavity or through via 510, instead of cutting the wafer, the U-turn chip 502 is attached and suspended by a flexure 509. The U-turn chip 502 is restricted from out-of-plane motion but has a small degree of freedom to move in-plane. This ensures vertical alignment between the PIC 505, the SOA array chip 501, and the U-turn chip 502, but allows the U-turn chip 502 to move left or right to accommodate changes in the length of the SOA array chip 501. During assembly, the pre-assembled SOA 501 on the carrier 503 is inverted, aligned, and bonded to the pedestal (e.g., pedestal 506) of the PIC chip 505. The U-turn chip 502 is then pushed toward the SOA array chip 501 and permanently fixed in place with adhesive 508 to form the PIC assembly 500.

[0041] Figure 6 illustrates a PIC assembly 600 including a U-turn chip 602 and multiple comb drives 611 from which a PIC chip 605 is suspended according to one or more embodiments. The comb drives 611 are added to use electrostatic force to move the U-turn chip 602 in a plane. As shown, the comb drives 611 are configured to control the translation of the U-turn chip 602 relative to the SOA array chip 601 in two orthogonal directions. The comb drives 611 are formed from portions of the U-turn chip 602 and the PIC chip 605 and are configured to position the U-turn chip 602 relative to the SOA array chip 601. Once the waveguide of the SOA array chip 601 is aligned with the waveguide of the U-turn chip 602, adhesive 608 is applied to permanently fix the U-turn chip 602 in place. Three comb drives 611 are shown, but in other embodiments, the PIC chip 605 may include one or more comb drives 611.

[0042] Figure 7 shows a top-down view of a PIC assembly 700 including an external cavity laser according to one or more embodiments. The PIC assembly 700 includes one SOA array chip 110 and one Gain Medium Chip 701, which are packaged into a PIC chip 702 including a resonator 718 with the help of a U-turn chip 113. The Gain Medium Chip 701 and the resonator 718 form an External Cavity Laser (ECL), which is the laser source in this embodiment. The resonator 718 and the Gain Medium Chip 701 collectively select and amplify specific bands of the emitted light.

[0043] Light from the ECL source is coupled to the SOA array chip 110 via waveguide 705. The SOA array chip 110 operates with in-coupled light in the manner described above in relation to Figure 1.

[0044] Additional configuration information The drawings and the preceding description relate to preferred embodiments for illustrative purposes only. As stated above, it should be noted that alternative embodiments of the structures and methods disclosed herein are readily recognizable as viable alternatives that can be adopted without departing from the principles of the claims.

[0045] The detailed description includes numerous details, which should not be construed as limiting the scope of the invention, but merely as illustrating different examples. It should be understood that the scope of this disclosure includes other embodiments not described in detail above. Various other variations, alterations, and modifications are possible with respect to the arrangement, operation, and details of the methods and apparatus disclosed herein, without departing from the idea and scope defined in the appended claims, which are obvious to those of the ordinary art. Therefore, the scope of the invention should be determined by the appended claims and their legal equivalents.

[0046] Alternative embodiments are implemented in computer hardware, firmware, software, and / or combinations thereof. An example implementation may be implemented as a computer program product substantially embodied in a machine-readable storage device for execution by a programmable processor, and the method steps may be performed by a programmable processor that executes an instruction program to perform a function by acting on input data and producing an output. Advantageously, embodiments can be implemented in one or more computer programs executable on a programmable system including a data storage system, at least one input device, and at least one output device, coupled with at least one programmable processor to receive data and instructions from and transmit data and instructions therefrom. Each computer program may be implemented in a highly procedural or object-oriented programming language or, if necessary, assembly or machine code, and in any case, the language may be a compiled or interpreted language. Suitable processors include, as an example, general-purpose and special-purpose microprocessors. Generally, the processor receives instructions and data from read-only memory (ROM) and / or random-access memory (RAM). Generally, a computer includes one or more high-capacity storage devices for storing data files, such devices including magnetic disks, magneto-optical disks, and optical disks, such as internal hard disks and removable disks. Storage devices suitable for substantially implementing computer program instructions and data include, for example, semiconductor memory devices such as EPROMs, EEPROMs, and flash memory devices, magnetic disks, magneto-optical disks, and all forms of non-volatile memory, such as internal hard disks and removable disks, and CD-ROM disks. All of the foregoing may be complemented or integrated with application-specific integrated circuits (ASICs) and other forms of hardware.

Claims

1. A LiDAR (Light Detection and Distance Measurement) system for a vehicle, comprising: a semiconductor optical amplifier (SOA) chip; and an optical splitter configured to receive input light propagating from the SOA chip and to split the input light into a plurality of beams, The aforementioned SOA chip is At least one first SOA that emits amplified light passing through the SOA chip in a first direction, At least one second SOA that emits amplified light passing through the SOA chip in a second direction, A specific chip facet, wherein the optical input and optical output of the SOA chip are located on the specific chip facet, The at least one first SOA and the at least one second SOA are configured to provide different amplification amounts. The at least one second SOA that emits amplified light passing through the SOA chip in the second direction comprises a specific number of second SOAs, each coupled to a specific number of waveguides that receive the plurality of beams from the optical splitter. LiDAR system.

2. The LiDAR system according to claim 1, wherein the at least one first SOA emitting amplified light in the first direction performs pre-amplification to offset losses associated with chip-to-chip coupling between the SOA chip and adjacent chips.

3. The LiDAR system according to claim 1, wherein the at least one second SOA that emits amplified light in the second direction performs the amplification of received light to a predetermined output level.

4. The LiDAR system according to claim 1, wherein the SOA chip comprises a III-V compound semiconductor material.

5. The LiDAR system according to claim 1, further comprising a light source for supplying a light beam to the optical input of the SOA chip.

6. The optical output of the SOA chip provides multiple amplified beams toward the surroundings of the vehicle. The LiDAR system according to claim 5, wherein the plurality of amplified beams are configured to reflect from the surrounding objects.

7. The LiDAR system according to claim 1, wherein the LiDAR system is part of a frequency-modulated continuous wave (FMCW) LiDAR system.

8. The LiDAR system according to claim 1, wherein the first direction is parallel to and opposite to the second direction.

9. An autonomous vehicle (AV) control system comprising one or more processors for executing instructions based on signals from a LiDAR system, The LiDAR system comprises a semiconductor optical amplifier (SOA) chip and an optical splitter configured to receive input light propagating from the SOA chip and to split the input light into a plurality of beams. The aforementioned SOA chip is At least one first SOA that emits amplified light passing through the SOA chip in a first direction, At least one second SOA that emits amplified light passing through the SOA chip in a second direction, A specific chip facet, wherein the optical input and optical output of the SOA chip are located on the specific chip facet of the SOA chip, The at least one first SOA and the at least one second SOA are configured to provide different amplification amounts. The at least one second SOA that emits amplified light passing through the SOA chip in the second direction comprises a specific number of second SOAs, each coupled to a specific number of waveguides that receive the plurality of beams from the optical splitter. Autonomous vehicle control system.

10. The AV control system according to claim 9, wherein the at least one first SOA emitting amplified light in the first direction performs pre-amplification to offset losses associated with chip-to-chip coupling between the SOA chip and adjacent chips.

11. The AV control system according to claim 9, wherein the at least one second SOA that emits amplified light in the second direction performs the amplification of received light to a predetermined output level.

12. The AV control system according to claim 9, wherein the SOA chip comprises a III-V compound semiconductor material.

13. The AV control system according to claim 9, further comprising a light source for providing a light beam to the optical input of the SOA chip.

14. The optical output of the SOA chip provides multiple amplified beams toward the surroundings of the autonomous vehicle. The AV control system according to claim 9, wherein the plurality of amplified beams are configured to reflect from the surrounding objects.

15. The AV control system according to claim 9, wherein the AV control system is part of a frequency-modulated continuous wave (FMCW) LiDAR system.

16. An autonomous vehicle equipped with an autonomous vehicle control system, The aforementioned autonomous vehicle control system comprises one or more processors for executing instructions based on signals from a LiDAR system. The LiDAR system comprises a semiconductor optical amplifier (SOA) chip and an optical splitter configured to receive input light propagating from the SOA chip and to split the input light into a plurality of beams. The aforementioned SOA chip is At least one first SOA that emits amplified light passing through the SOA chip in a first direction, At least one second SOA that emits amplified light passing through the SOA chip in a second direction, A specific chip facet, wherein the optical input and optical output of the SOA chip are located on the specific chip facet of the SOA chip, The at least one first SOA and the at least one second SOA are configured to provide different amplification amounts. The at least one second SOA that emits amplified light passing through the SOA chip in the second direction comprises a specific number of second SOAs, each coupled to a specific number of waveguides that receive the plurality of beams from the optical splitter. Self-driving cars.

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