An OPA receiver antenna chip

Abstract

An OPA (Optical Phased Array) receiving antenna chip, belonging to the field of optical phased array antenna technology, addresses the problem of low receiving efficiency in existing silicon-based optical phased array antennas. A grating waveguide array layer and a waveguide transmission layer constitute a planar grating receiving and transmission structure. Incident light received by the chip passes through the planar waveguide. The grating waveguide array layer generates periodic refractive index perturbations on the planar waveguide. When the incident light received by the chip passes through the planar waveguide, its first-order diffracted light propagates along the planar waveguide, then through a tapered waveguide into a superlattice waveguide, and finally outputs from the superlattice waveguide. This invention, through its planar grating receiving and transmission structure, enables the chip to efficiently receive incident light and transmit it to the superlattice waveguide output, achieving a 100% duty cycle and significantly improving optical coupling efficiency and received optical power. The superlattice waveguide and adiabatic tapered waveguide structure effectively reduce transmission loss and optical field crosstalk.

Description

Technical Field

[0001] This invention belongs to the field of optical phased array antenna technology and relates to an OPA receiving antenna chip. Background Technology

[0002] Currently, phased array antennas in optical phased arrays (OPA) are difficult to integrate for both transmitting and receiving. They are only used to transmit beams, and echo signals are mostly received using spatial optical paths and detector arrays. This does not conform to the current trend of device integration and miniaturization, and hinders the development of vehicle-mounted and airborne lidar systems towards lightweight, low-power, and low-cost directions. Therefore, research on OPA receiving antennas is of great significance for reducing the size, power consumption, and cost of lidar systems.

[0003] The main reasons why OPA antennas are currently difficult to use for reception are high reception loss and small aperture: 1) Phased array antennas have high coupling strength. If the antenna length is long, light traveling from free space through the phased array antenna and coupled into the waveguide will radiate back into free space, resulting in power loss; 2) Phased array antennas have a low duty cycle. Phased array antennas consist of periodically arranged antenna elements with a certain duty cycle, and each element can only cover a certain receiving area. When receiving parallel light from a distance, some light shines into the blank area and cannot couple into the optical waveguide, resulting in optical power loss.

[0004] With the increasing demand for all-solid-state LiDAR in autonomous driving technology, the disadvantages of traditional mechanical LiDAR, such as large size, heavy weight, and high power consumption, are no longer suitable for current application scenarios. Optical phased array (OPA) technology, as a new approach to realizing all-solid-state LiDAR, has gradually attracted attention. OPA is an electronically controlled scanning beam pointing control technology with excellent performance in terms of non-mechanical deflection capability, wide field of view, low power consumption, and lightweight design, which can well meet the application requirements of all-solid-state LiDAR.

[0005] Currently, phased array antennas in optical phased arrays (OPA) are difficult to integrate for both transmitting and receiving. They are only used to transmit beams, and echo signals are mostly received using spatial optical paths and detector arrays. This does not conform to the current trend of device integration and miniaturization, and hinders the development of vehicle-mounted and airborne lidar systems towards lightweight, low-power, and low-cost directions. Therefore, research on OPA receiving antennas is of great significance for reducing the size, power consumption, and cost of lidar systems.

[0006] There are many ways to implement OPA (Optical Photonic Amplifier), among which silicon-based waveguide OPA has been favored by researchers due to its fast response speed, large scanning angle, and high integration density. The development of silicon-on-insulator (SOI) technology, which is compatible with complementary metal-oxide-semiconductor (CMOS) process lines, has provided a solid foundation for large-scale silicon photonic integration. Therefore, silicon-based OPA chips have gradually become a research hotspot in the field of lidar in recent years.

[0007] Currently, silicon-based OPAs typically use grating couplers or waveguide gratings as the unit structure for the array antenna. Grating couplers have high optical coupling efficiency, but the structure is relatively large, resulting in a low duty cycle and thus high overall receiving loss. Waveguide grating-based phased array antennas usually use single-mode waveguides, resulting in a small receiving area, low coupling efficiency, and a large antenna spacing to prevent crosstalk between waveguides, which also leads to a low duty cycle.

[0008] In two-dimensional grating antenna arrays, grating couplers offer advantages such as high coupling efficiency and small size. However, their scale or aperture is difficult to increase, and their duty cycle is low. In one-dimensional grating antennas, waveguide gratings reduce the number of two-dimensional antennas by increasing the longitudinal propagation length, but the lateral layout remains a discrete antenna structure. To avoid crosstalk between antennas, a large gap is required between adjacent antennas, and waveguide gratings typically use narrow single-mode waveguides. This results in a low duty cycle for the antenna array, thus affecting the receiving efficiency. Summary of the Invention

[0009] The technical solution of the present invention is used to solve the problem of low receiving efficiency of silicon-based optical phased array antennas in the prior art.

[0010] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0011] This invention provides an OPA receiving antenna chip, comprising: a substrate layer, an intermediate cladding layer, and an upper cladding layer stacked sequentially from bottom to top; the intermediate cladding layer sequentially includes a buried layer, a grating waveguide array layer, a conditioning layer, and a waveguide transmission layer, wherein the grating waveguide array layer consists of multiple strip waveguides arranged in an array along the x-axis direction, and the waveguide transmission layer includes a planar waveguide, a tapered waveguide, and a superlattice waveguide; the planar waveguide connects to multiple tapered waveguides, and the tapered waveguide connects to the superlattice waveguide; the grating waveguide array layer and the waveguide transmission layer constitute a planar grating receiving and transmission structure, the incident light received by the chip passes through the planar waveguide, the grating waveguide array layer generates periodic refractive index perturbations on the planar waveguide, when the incident light received by the chip passes through the planar waveguide, its first-order diffracted light will be transmitted along the planar waveguide, then transmitted through the tapered waveguide into the superlattice waveguide, and finally output from the superlattice waveguide.

[0012] Furthermore, the sum of the base widths of the plurality of said tapered waveguides is equal to the width of the planar waveguide.

[0013] Furthermore, adjacent superlattice waveguides have different widths.

[0014] Furthermore, the substrate layer is used to support the chip, and the material of the substrate layer is silicon.

[0015] Furthermore, the upper cladding layer is used to protect the waveguide transmission layer, and the material of the upper cladding layer is silicon dioxide.

[0016] Furthermore, the buried layer serves to separate the substrate layer from the grating waveguide array layer.

[0017] Furthermore, the thickness of the adjustment layer is adjustable, and its function is to adjust the spacing between the grating waveguide array layer and the waveguide transmission layer.

[0018] Preferably, both the burial layer and the conditioning layer are made of silicon dioxide.

[0019] Preferably, the material of the grating waveguide array layer is silicon nitride.

[0020] Preferably, the waveguide transmission layer is made of silicon.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention utilizes a planar grating receiving and transmitting structure, enabling the chip to efficiently receive incident light and transmit it to a superlattice waveguide output, achieving a 100% duty cycle and significantly improving optical coupling efficiency and received optical power. The use of a silicon nitride grating, with its low refractive index and ease of fabrication, overcomes the limitations of traditional silicon grating processes and supports greater longitudinal length. The superlattice waveguide and adiabatic tapered waveguide structures effectively reduce transmission loss and optical field crosstalk. The chip's compact structure meets the lightweight and low-power requirements of automotive and airborne LiDAR. Compatible with CMOS processes, it is suitable for mass production, reducing costs. The separate design of the receiving and transmitting sections allows for independent performance optimization, improving overall efficiency. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural front perspective view of the OPA receiving antenna chip according to an embodiment of the present invention;

[0024] Figure 2 This is a front perspective view of the OPA receiving antenna chip in the xoz plane according to an embodiment of the present invention;

[0025] Figure 3 This is a yoz planar perspective view of the OPA receiving antenna chip according to an embodiment of the present invention;

[0026] Figure 4 This is a top perspective view of the OPA receiving antenna chip according to an embodiment of the present invention;

[0027] Figure 5 This is a three-dimensional structural front view of the grating waveguide array layer and waveguide transmission layer of the OPA receiving antenna chip according to an embodiment of the present invention;

[0028] Figure 6 This is a top view of the grating waveguide array layer and waveguide transmission layer of the OPA receiving antenna chip according to an embodiment of the present invention;

[0029] Figure 7 This is a yoz planar side view of the grating waveguide array layer and waveguide transmission layer of the OPA receiving antenna chip according to an embodiment of the present invention;

[0030] Figure 8 This is a front view of the grating waveguide array layer and waveguide transmission layer of the OPA receiving antenna chip according to an embodiment of the present invention;

[0031] Figure 9 This is a dimensional design diagram of the grating waveguide array layer and waveguide transmission layer of the OPA receiving antenna chip according to an embodiment of the present invention;

[0032] Figure 10 This is a schematic diagram of the incident light transmission of the grating waveguide array layer and waveguide transmission layer of the OPA receiving antenna chip according to an embodiment of the present invention;

[0033] Figure 11 This is a simulation result curve of the receiving efficiency of the OPA receiving antenna chip according to an embodiment of the present invention;

[0034] Figure 12 This is a diagram of a traditional silicon flat panel grating antenna structure. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0037] Example 1

[0038] exist Figures 1 to 3 , Figure 5 , Figure 7 and Figure 8 In this case, the incident direction of light is the negative direction of the z-axis.

[0039] like Figures 1 to 4 As shown, the OPA receiving antenna chip of this embodiment includes a substrate layer 10, an intermediate cladding layer 11, and an upper cladding layer 12, which are stacked sequentially from bottom to top along the positive z-axis.

[0040] like Figure 2 and Figure 3 As shown, the intermediate cladding layer 11 includes: a buried layer 110, a grating waveguide array layer 111, an adjustment layer 112, and a waveguide transmission layer 113, which are stacked sequentially from bottom to top along the positive z-axis direction.

[0041] The substrate layer 10 serves as the bottom layer of the OPA receiving antenna chip, providing support. The substrate layer 10 is made of silicon. The buried layer 110 separates the substrate layer 10 from the grating waveguide array layer 111. The thickness of the adjustment layer 112 is adjustable, and its function is to adjust the spacing between the grating waveguide array layer 111 and the waveguide transmission layer 113. Both the buried layer 110 and the adjustment layer 112 are made of silicon dioxide, the grating waveguide array layer 111 is made of silicon nitride, and the waveguide transmission layer 113 is made of silicon. The upper cladding layer 12 is located on the top layer of the chip and is used to protect the waveguide transmission layer 113. The upper cladding layer 12 is made of silicon dioxide.

[0042] like Figures 5 to 8 As shown, the grating waveguide array layer 111 includes multiple strip waveguides 1111, and the waveguide transmission layer 113 includes a planar waveguide 1131, a tapered waveguide 1132, and a superlattice waveguide 1133. The multiple strip waveguides 1111 are arranged in an array along the x-axis direction. One end of the planar waveguide 1131 is connected to multiple tapered waveguides 1132, and one end of the tapered waveguide 1132 is connected to a superlattice waveguide 1133. The sum of the widths of the bottom edges of the multiple tapered waveguides 1132 is equal to the width of the planar waveguide 1131, and the length of the strip waveguide 1111 is equal to the width of the planar waveguide 1131. The length direction of the strip waveguide 1111 is the y-axis direction, the length direction of the planar waveguide 1131 is the x-axis direction, and the width direction of the planar waveguide 1131 is the y-axis direction.

[0043] like Figure 9 As shown, the planar waveguide 1131 has a width of 7.5 μm and a length of 200 μm. The planar waveguide 1131 covers the entire grating waveguide array layer 111. The five tapered waveguides 1132 have a length L1 of 21 μm and a base width w6 of 1.5 μm. The sum of the base widths of the five tapered waveguides 1132 and the planar waveguide 1131... The widths of the five superlattice waveguides 1133 are equal, with widths divided into w1, w2, w3, w4, and w5, which are 410 nm, 430 nm, 450 nm, 470 nm, and 490 nm, respectively. The widths of adjacent superlattice waveguides 1133 are different, so that each superlattice waveguide 1133 has a different effective refractive index, which can avoid optical field crosstalk. The width a of the strip waveguide 1111 is 420 nm, and the period d is 600 nm.

[0044] The working principle of the OPA receiving antenna chip in this embodiment of the invention is as follows:

[0045] like Figure 10As shown, the grating waveguide array layer 111 and the waveguide transmission layer 113 constitute a planar grating receiving and transmitting structure. The incident light received by the chip passes through the planar waveguide 1131. The grating waveguide array layer 111 generates periodic refractive index perturbations on the planar waveguide 1131. According to the principle of light diffraction, this will cause the first-order diffracted light to be transmitted along the planar waveguide 1131 when the incident light received by the chip passes through the planar waveguide 1131 (as shown by the red arrow in the figure), and then transmitted into the superlattice waveguide 1133 through the tapered waveguide 1132, and finally output from the superlattice waveguide 1133.

[0046] Furthermore, in this embodiment of the invention, since the sum of the bottom widths of the multiple tapered waveguides 1132 is equal to the width of the planar waveguide 1131, all the light transmitted in the planar waveguide 1131 is output through the tapered waveguide 1132, thereby improving the light utilization rate.

[0047] The OPA receiving antenna chip of this invention achieves high-efficiency antenna reception, such as... Figure 11 As shown, the receiving efficiency is 25% as determined by FDTD optical simulation software.

[0048] Typically, optical phased array receiving antennas consist of an array of multiple discrete grating waveguides. The grating waveguides couple light from space into the waveguide and then transmit it separately along the horizontal direction. Since each grating waveguide is a separate path, adjacent waveguides need to be separated by a distance to avoid crosstalk between them. This results in a non-100% duty cycle in the Y direction. Some of the light illuminating the antenna surface passes through the blank areas between the grating waveguides and cannot enter the waveguide itself. The advantages of planar gratings are that their lateral length covers the length of the planar waveguide, achieving a 100% duty cycle and significantly increasing the contact area with light compared to traditional waveguide gratings, thus increasing the total light intake. Silicon nitride gratings are larger in size and easier to fabricate, and their low refractive index (around 2) minimizes refractive index disturbances in the silicon planar waveguide. These two factors allow for a larger array size, meaning the longitudinal length can reach 200 μm. Figure 12As shown, a traditional silicon planar grating consists of two silicon layers: a silicon grating and a silicon planar waveguide layer, with a total thickness h2 of 220 nm. The grating structure is formed by etching, and the standard etching depth h1 is 150 nm. Simulations using this structure yielded receiving efficiencies of 6%, 3.2%, 2.2%, and 1.7% for lengths of 20, 40, 60, and 80 μm, respectively. The receiving efficiency decreases with increasing length. Simulations were then performed for a length of 80 μm, with h1 values ​​of 120 nm, 100 nm, 80 nm, 60 nm, 40 nm, and 20 nm, yielding receiving efficiencies of 2%, 2.7%, 4%, 7%, 13%, and 14.6%, respectively. This shows that the receiving efficiency gradually increases with decreasing etching depth at this length. The reason for this is that the refractive index change introduced by the grating gradually decreases, specifically 0.66, 0.5, 0.37, 0.25, 0.15, and 0.07. Therefore, the smaller the refractive index change, the longer the grating length can be achieved. However, for silicon waveguides, the etching depth is very small, making it difficult to achieve in terms of manufacturing processes. The grating-based structure proposed in this invention solves this problem. Silicon nitride has a low refractive index, so the grating height can be large, reaching 300 nm, while the refractive index difference is small, at 0.02, thus enabling a longer length, reaching 200 μm.

[0049] The OPA receiving antenna chip of this invention improves the duty cycle of the grating antenna, greatly enhancing the receiving efficiency. Simultaneously, the weak coupling strength and large structural size of the silicon nitride grating increase the longitudinal length of the antenna, significantly improving the received optical power. The antenna is divided into two parts, a receiving section and a transmitting section, which are designed separately to improve the efficiency of each. Superlattice waveguides and thermally adiabatic tapered waveguides are used to reduce optical power crosstalk and transmission loss.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An OPA receiving antenna chip, characterized in that, include: The substrate layer (10), intermediate cladding layer (11), and upper cladding layer (12) are stacked sequentially from bottom to top. The intermediate cladding layer (11) includes a buried layer (110), a grating waveguide array layer (111), a conditioning layer (112), and a waveguide transmission layer (113). The grating waveguide array layer (111) consists of multiple strip waveguides (1111) arranged in an array along the x-axis. The waveguide transmission layer (113) includes a planar waveguide (1131), a tapered waveguide (1132), and a superlattice waveguide (1133). One end of the planar waveguide (1131) is connected to multiple tapered waveguides (1132), and one end of the tapered waveguide (1132) is connected to a superlattice waveguide (1133). The sum of the widths of the bottom edges of the multiple tapered waveguides (1132) is equal to the sum of the widths of the bottom edges of the tapered waveguides (1132). The length of the strip waveguide (1111) is equal to the width of the planar waveguide (1131). The grating waveguide array layer (111) and the waveguide transmission layer (113) constitute a planar grating receiving and transmitting structure. The incident light received by the chip passes through the planar waveguide (1131). The grating waveguide array layer (111) generates periodic refractive index perturbations on the planar waveguide (1131). When the incident light received by the chip passes through the planar waveguide (1131), its first-order diffracted light will be transmitted along the planar waveguide (1131), and then transmitted through the tapered waveguide (1132) into the superlattice waveguide (1133), and finally output from the superlattice waveguide (1133). The widths of adjacent superlattice waveguides (1133) are different.

2. The OPA receiving antenna chip according to claim 1, characterized in that, The substrate (10) is used to support the chip, and the material of the substrate (10) is silicon.

3. The OPA receiving antenna chip according to claim 1, characterized in that, The upper cladding (12) is used to protect the waveguide transmission layer (113), and the material of the upper cladding (12) is silicon dioxide.

4. The OPA receiving antenna chip according to claim 1, characterized in that, The buried layer (110) serves to separate the substrate layer (10) from the grating waveguide array layer (111).

5. The OPA receiving antenna chip according to claim 1, characterized in that, The thickness of the adjustment layer (112) is adjustable, and its function is to adjust the spacing between the grating waveguide array layer (111) and the waveguide transmission layer (113).

6. The OPA receiving antenna chip according to claim 1, characterized in that, The materials of the buried layer (110) and the regulating layer (112) are both silicon dioxide.

7. The OPA receiving antenna chip according to claim 1, characterized in that, The material of the grating waveguide array layer (111) is silicon nitride.

8. The OPA receiving antenna chip according to claim 1, characterized in that, The waveguide transmission layer (113) is made of silicon.

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