Silicon-based optical phased array receiving antenna based on double-layer SiN-Si structure

Abstract

The invention discloses a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure, the receiving antenna comprises an SOI substrate, a metal reflecting layer and a Si grating layer, the SOI substrate at least comprises a substrate silicon layer, a buried oxide layer and a top SiN waveguide layer, the metal reflecting layer is located in the buried oxide layer, the upper part and the lower part of the metal reflecting layer are respectively adjacent to a SiN waveguide and the substrate silicon layer, and the Si grating layer is located in the buried oxide layer. The SiN waveguide is used for transmitting a light field coupled by the Si grating layer, the Si grating layer is positioned above the SiN waveguide, and SiO2 is filled between the two layers and is used for coupling spatial light into the SiN waveguide at the lower layer. According to the embodiment of the invention, the double-layer SiN-Si silicon-based receiving antenna structure is designed, the two-dimensional diffraction grating structure is used for receiving vertically incident planar far-field light, the structure can more efficiently couple light field energy into the SiN waveguide, and the receiving capability of the optical phased array antenna is improved.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure. Background Art

[0002] The concept of phased array LiDAR has been proposed for a long time, and various design schemes are being developed. Its basic modules are also mature, such as light source, beam splitting, phase modulation, etc. However, how to improve the receiving coupling efficiency of far-field parallel light is still a huge challenge. This is because the near-vertical incidence of far-field parallel light will lead to poor reflection and diffraction directionality, and some light will be scattered to the substrate to cause energy loss. In addition, the light intensity loss caused by the error in the polarization direction of the incident light and the mode coupling loss caused by the mode field mismatch will lead to a decrease in the antenna receiving efficiency, which seriously affects the receiving performance of the silicon-based optical phased array.

[0003] At present, the mainstream silicon-based optical phased arrays mostly use single-layer fishbone antenna structures or chain antenna structures, which can achieve good transmission performance, but the receiving efficiency of this type of antenna is not high, and most of the light field energy is reflected or transmitted into the silicon substrate, causing energy loss. In recent years, multi-layer antenna structures have emerged, among which the double-layer antenna structure can effectively introduce refractive index differences in the vertical direction and improve the transmission and reception efficiency. However, there is currently no work to optimize the antenna's receiving efficiency. The insufficient receiving efficiency of silicon-based phased array antennas restricts its development potential in the fields of laser radar ranging and communications. Summary of the invention

[0004] The present invention aims to address the deficiencies of the prior art and to propose a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure, so as to solve the problem of low receiving efficiency of silicon-based phased array antennas in the prior art.

[0005] The objective of the present invention is achieved through the following technical solution: a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure, the optical phased array receiving antenna comprising:

[0006] An SOI substrate, wherein the SOI substrate comprises at least a substrate silicon layer, a buried oxide layer and a top SiN waveguide layer from bottom to top, wherein the SiN waveguide layer is used to transmit an optical field coupled by the Si grating layer;

[0007] A metal reflective layer, the metal reflective layer being located at a junction of the substrate silicon layer of the SOI substrate and the buried oxide layer;

[0008] Si grating layer, the Si grating layer is located above the SiN waveguide, the filling material between the two layers is SiO2, and the spatial light is coupled to the SiN waveguide in the lower layer; the Si grating layer is a two-dimensional diffraction grating.

[0009] Furthermore, when free-space light is transmitted to the area where the two-dimensional diffraction grating is located, refraction and reflection will be formed between the gratings, wherein the refracted light waves will enter the lower layer of the two-dimensional diffraction grating and form coupling in the SiN waveguide; part of the light field continues to be transmitted downward and will be reflected again when it reaches the metal reflective layer, so that the light waves can be coupled into the waveguide by the grating again.

[0010] Furthermore, the area where the metal reflective layer is located corresponds to the area where the optical antenna array is located, and is larger than the area where the optical antenna array is located.

[0011] Furthermore, the thickness of the metal reflective layer corresponds to the metal material type of the metal reflective layer and the optical wave band processed by the optical phased array receiving antenna.

[0012] Furthermore, the waveguide array is a row of horizontally arranged waveguides.

[0013] Furthermore, the Si grating layer is formed by two one-dimensional Si gratings arranged at intervals to enhance coupling efficiency; the width of each grating is less than 0.4um to prevent the formation of a fundamental mode in the grating;

[0014] Furthermore, the antenna is structurally designed and optimized based on the FDTD finite-difference time-domain method.

[0015] Beneficial effects of the present invention: The antenna design for receiving a silicon-based optical phased array based on a double-layer SiN-Si structure provided by the present invention utilizes a two-dimensional diffraction grating structure to receive vertically incident planar far-field light, and prevents the formation of a fundamental mode in the grating by reducing the grating width, so that the light field energy can be coupled to the SiN waveguide of the lower layer, and two rows of gratings are designed on each SiN waveguide to enhance the coupling efficiency. This structure can more efficiently couple the light field energy into the SiN waveguide, thereby improving the receiving capability of the optical phased array antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 This is a schematic diagram of the structure of a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to an embodiment of the present invention;

[0018] Figure 2 A top view of a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the interlayer structure of a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to an embodiment of the present invention;

[0020] Figure 4 is a cross-sectional view of a Si grating layer according to an embodiment of the present invention;

[0021] Figure 5 This is an optimization flow chart based on the FDTD finite-difference time-domain method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure, wherein the optical antenna comprises:

[0024] An SOI substrate, wherein the SOI substrate comprises at least a substrate silicon layer 10, a buried oxide layer 20 and a top SiN waveguide layer 30 in sequence from bottom to top;

[0025] A metal reflective layer 11, wherein the metal reflective layer 11 is located at a junction of the substrate silicon layer 10 and the buried oxide layer 20 of the SOI substrate;

[0026] The Si grating layer 40 is located above the SiN waveguide 30, and the SiO2 material 50 is filled between the two layers to couple the spatial light into the lower SiN waveguide 30. The SiN waveguide 30 is used to transmit the light field coupled by the Si grating layer 40.

[0027] Optical antennas are used to transmit or receive light beams and can be applied to many optical devices, such as phased array laser radars. The optical antenna is specifically an electronic device integrated on a piece of CMOS semiconductor material, of which the most commonly used CMOS semiconductor material is the SOI substrate. The material and thickness of each layer of the SOI substrate from bottom to top can be customized according to different requirements. For the convenience of expression, in the following embodiments, the optical antenna of the embodiment of the present invention is integrated using the above-mentioned standard CMOS process SOI substrate as the SOI substrate.

[0028] The SiN waveguide array on the top of the SOI substrate is specifically a row of horizontally arranged waveguides with equal width.

[0029] The Si grating layer 40 is located above the SiN waveguide. Figure 3 As shown, SiO2 material 50 is used to fill the space between the Si grating layer 40 and the SiN waveguide layer 30. The Si grating layer is composed of two one-dimensional Si gratings A60 and grating B 70 arranged alternately. Figure 4 As shown, there is a certain distance between the grating A 60 and the grating B 70, and the actual distance parameter is determined by simulation based on the FDTD finite difference time domain method. The Si grating layer 40 forms a two-dimensional diffraction grating, and the formation of the fundamental mode in the grating is prevented by reducing the grating width, so that the light field energy can be coupled to the SiN waveguide in the lower layer, and two rows of gratings are designed on each SiN waveguide to enhance the coupling efficiency. This structure can more efficiently couple the light field energy into the SiN waveguide.

[0030] Optical antennas are used to receive or transmit light waves. Since the wavelengths of light waves vary greatly, it is impossible for one optical antenna design to meet the needs of all light waves. Even if the same design concept can be used, the various parameters will need to change accordingly according to the wavelengths of light waves processed by the optical antenna, such as 1.5 to 1.6 μm. For the sake of convenience, the following embodiments are described using the wavelength of light waves of 1.5 to 1.6 μm as an example.

[0031] When the spatial plane light 90 enters the area where the Si grating layer 40 is located from the free space, refraction and reflection will be formed in the grating layer, wherein the refracted light wave will be captured by the grating and coupled in the SiN waveguide layer 30, thereby achieving the purpose of the optical antenna receiving and coupling the free space light, while at the same time, part of the refracted light wave will pass through the SiN waveguide layer and be absorbed by the underlying substrate silicon layer 10, which is obviously not good for the receiving efficiency of the entire optical antenna. For this reason, a metal reflection layer 11 is formed at the junction of the substrate silicon layer 10 of the SOI substrate and the buried oxide layer 20, and the metal reflection layer 11 will reflect the light wave passing through the SiN waveguide 30 back again, so that more light waves can be coupled and enter the SiN waveguide 30, forming a fundamental mode light field 100 propagating in the SiN waveguide, thereby improving the receiving efficiency of the entire optical antenna.

[0032] Based on the above embodiment, further, the area where the metal reflective layer 11 is located corresponds to the area where the optical antenna array is located, and is larger than the area where the optical array antenna is located.

[0033] When the optical antenna forms a metal reflective layer, the area and size of the metal reflective layer need to be determined first. Since the metal reflective layer is used to reflect the light waves reflected by the grating, the metal reflective layer needs to correspond to the area where the grating is located, that is, directly below the two-dimensional diffraction grating. At the same time, considering the angle of light wave emission, the area where the metal reflective layer is located also needs to be larger than the area where the grating is located. For example, the side length of the metal reflective layer is 10 to 20 μm longer than the side length of the area where the grating is located.

[0034] Furthermore, the thickness of the metal reflective layer corresponds to the metal material type of the metal reflective layer and the light wave band processed by the optical antenna.

[0035] Based on the above embodiment, further, the antenna array is a row of horizontally arranged waveguides. There are many ways to arrange the waveguide array, such as uniform arrangement, that is, the spacing between adjacent waveguides is the same. Uniform arrangement is the simplest and most convenient, but it also brings defects such as high grating lobes and large far-field divergence angles, while non-uniform arrangement will lead to a decrease in receiving efficiency and chip integration. After comprehensively weighing the receiving field of view and receiving efficiency, the design arrangement is a uniform arrangement.

[0036] The above design values ​​refer to the FDTD finite time-domain method. The design idea of ​​the finite time-domain method is as follows: Figure 5 As shown, by scanning and simulating the key parameters of the antenna, the optimized antenna can achieve a fundamental mode receiving efficiency of 20%.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure, characterized in that: The optical phased array receiving antenna comprises: An SOI substrate, wherein the SOI substrate comprises at least a substrate silicon layer, a buried oxide layer and a top SiN waveguide layer from bottom to top, wherein the SiN waveguide layer is used to transmit an optical field coupled by the Si grating layer; A metal reflective layer, the metal reflective layer being located at a junction of the substrate silicon layer of the SOI substrate and the buried oxide layer; Si grating layer, the Si grating layer is located above the SiN waveguide, the filling material between the two layers is SiO2, and the spatial light is coupled to the SiN waveguide in the lower layer; the Si grating layer is a two-dimensional diffraction grating.

2. The silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to claim 1, characterized in that: When free-space light is transmitted to the area where the two-dimensional diffraction grating is located, refraction and reflection will be formed between the gratings, wherein the refracted light wave will enter the lower layer of the two-dimensional diffraction grating and form coupling in the SiN waveguide; part of the light field continues to transmit downward and will be reflected again when it reaches the metal reflective layer, so that the light wave can be coupled into the waveguide by the grating again.

3. The silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to claim 1, characterized in that: The area where the metal reflective layer is located corresponds to the area where the optical antenna array is located, and is larger than the area where the optical antenna array is located.

4. The silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to claim 1, characterized in that: The thickness of the metal reflective layer corresponds to the metal material type of the metal reflective layer and the optical wave band processed by the optical phased array receiving antenna.

5. The silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to claim 1, characterized in that: The waveguide array is a row of waveguides arranged horizontally.

6. The silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to claim 1, characterized in that: The Si grating layer is formed by two one-dimensional Si gratings arranged at intervals to enhance coupling efficiency; the width of each grating row is less than 0.4um to prevent the formation of a fundamental mode in the grating.

7. The silicon-based optical phased array receiving antenna based on a double-layer SiN-Si structure according to claim 1, characterized in that: The antenna is structurally designed and optimized based on the FDTD finite difference time domain method.

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