Passive large-view-field silicon-based optical phased array
By adopting passive large field of view silicon-based optical phased array technology in optical phased arrays, and using multi-font and sinusoidal waveguide arrays to achieve phase regulation, the problems of large-angle scanning and high power consumption in the prior art are solved, and high-angle scanning with low power consumption and high-resolution beam control are achieved.
Patent Information
- Application Number
- CN202510246603.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-04
- Publication Date
- 2025-06-06
AI Technical Summary
The existing optical phased array technology is difficult to achieve large-angle scanning and has the problem of high power consumption.
Passive large field of view silicon-based optical phased array is adopted to achieve phase regulation through a multi-font waveguide array and a sinusoidal waveguide array, reduce power consumption, and achieve efficient beam splitting and phase delay of optical signals through silicon nitride material and multi-mode interference coupler.
It realizes high-angle scanning capability with low power consumption, improves the scanning angle and resolution of the beam, reduces the generation of side lobes, and significantly reduces system costs.
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Figure CN120103655A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of optoelectronic devices, and in particular to a passive large-field-of-view silicon-based optical phased array. Background Art
[0002] Optical phased array (OPA) technology is a technology that uses an array of multiple optical units to adjust the direction of the light beam by electronically controlling the phase difference between the optical units. Traditional phased array technology is used in the field of electromagnetic waves, such as radar and communication systems. However, introducing this technology into the optical field can achieve high-speed, precise, and non-moving parts beam control. The working principle of the optical phased array is based on the interference effect of light waves: by adjusting the optical path difference or phase difference between the array units, different interference patterns are generated, thereby guiding the light beam to focus or scan in different directions. Compared with the traditional mechanical scanning system, the advantages of the optical phased array are: it can complete the scanning of the light beam in nanoseconds or even shorter time; due to the short wavelength of the light wave, the optical phased array can control the light beam at a very high spatial resolution; the optical phased array does not have any movement of mechanical parts, which avoids mechanical loss and improves the stability and life of the system.
[0003] Passive optical phased array technology uses each waveguide array in the array to introduce a waveguide phase delay line to control the phase of the light wave, rather than relying on external power or signal drive. Beam control is achieved by changing the light path at the micro-nano scale.
[0004] Optical phased array technology controls the propagation direction of light waves by adjusting the phase of array elements, which makes it have very high precision and flexibility in beam scanning and beam pointing. Achieving large-angle scanning (i.e., large field of view) is a key technical challenge of optical phased arrays. The background of this technology involves many aspects, including phase control, array design, material selection, and the physical principles of beam propagation. Summary of the invention
[0005] Based on this, it is necessary to provide a passive large-field-of-view silicon-based optical phased array to solve the above-mentioned technical problems, thereby obtaining an optical phased array with low power consumption and capable of large-angle scanning.
[0006] A passive large-field-of-view silicon-based optical phased array, comprising:
[0007] Silicon substrate;
[0008] A silicon dioxide buried oxide layer, wherein the silicon dioxide buried oxide layer is disposed on the upper surface of the silicon substrate;
[0009] A silicon nitride layer, wherein the silicon nitride layer is arranged on the upper surface of the silicon dioxide buried oxide layer; the silicon nitride layer includes an inverted cone coupling waveguide, an optical beam splitting module, a phase delay module and a waveguide grating antenna module, wherein the inverted cone coupling waveguide is used to couple input light to the optical beam splitting module, the optical beam splitting module is used to equally split the optical signal generated by the input light into N equal-power sub-optical signals, the phase delay module includes a figure-of-feet waveguide array and a sinusoidal waveguide array, the figure-of-feet waveguide array is used to perform phase control on each sub-optical signal, so that any two adjacent sub-optical signals have the same phase difference, the sinusoidal waveguide array is used to reduce the waveguide spacing, and the waveguide grating antenna module is used to radiate the light energy output by the sinusoidal waveguide array, and N is greater than or equal to 2.
[0010] Optionally, the optical beam splitting module includes a plurality of cascaded multi-mode interference couplers.
[0011] Optionally, the cascaded multimode coupler divides the power of the optical signal into two, the input is a rectangular silicon nitride waveguide, the middle multimode interference coupling region is a larger rectangular silicon nitride waveguide, and the output is two rectangular silicon nitride waveguides of the same size as the input, wherein the length of the rectangular silicon nitride waveguide is 20 to 28 μm.
[0012] Optionally, the X-shaped waveguide array includes N waveguides, wherein the lengths of the N waveguides are different.
[0013] Optionally, the sinusoidal waveguide array includes N sinusoidal waveguides, wherein a distance between any two adjacent sinusoidal waveguides is smaller than a wavelength of the input light.
[0014] Optionally, the waveguide grating antenna module includes N waveguide gratings.
[0015] Optionally, the optical beam splitting module, the phase delay module and the waveguide grating antenna module are interconnected via a silicon nitride waveguide to achieve low-loss optical interconnection between different modules.
[0016] Optionally, the width of the silicon nitride waveguide ranges from 800 nm to 1000 nm.
[0017] Optionally, the height of the silicon substrate is greater than the height of the silicon dioxide buried oxide layer, and the height of the silicon dioxide buried oxide layer is greater than the height of the silicon nitride layer.
[0018] Optionally, the inverted cone coupling waveguide includes a gradient zone and a stable zone, the end of the gradient zone away from the stable zone is an input end, and the size of the gradient zone from the input end to the end of the gradient zone close to the stable zone gradually increases until it becomes the same as the size of the stable zone.
[0019] Compared with the prior art, the advantages of this application are:
[0020] 1. This application uses a "several" type waveguide structure, which can be calculated to have the same phase difference between each adjacent branch. Therefore, there is no need to add electricity to the optical phased array to achieve two-dimensional scanning of the OPA, which greatly reduces power consumption. In addition, the phase noise of this passive chip is very low, and the beam quality does not decrease as a result. The shape and length of the extension line can be flexibly designed to better meet the detection of the chip. Compared with traditional electrically adjustable and thermally adjustable optical phased arrays, this structure greatly reduces energy consumption and the quality of the beam does not decrease.
[0021] 2. This application uses a sinusoidal waveguide structure, which greatly reduces the spacing between waveguides, suppresses the generation of crosstalk between waveguides, greatly improves the scanning angle, and reduces the generation of side lobes. The beam scanning field of view of a one-dimensional optical phased array is related to the spacing between antenna elements. The smaller the spacing between elements, the larger the field of view. Based on the principle of refractive index mismatch, a sinusoidal curved structure is introduced to break the odd-even symmetry of the mode, thereby reducing the spacing between silicon nitride waveguides to below the wavelength, and the crosstalk between waveguides is also less than 20dB. This greatly improves the scanning angle of the optical phased array under the silicon nitride platform, thereby obtaining a large field of view and high resolution.
[0022] 3. The present application adopts cascading multiple MMIs for beam splitting, which can achieve uniform optical power for each channel and very low insertion loss for splitting. This can meet the integration of multiple OPAs and improve their efficiency and consistency.
[0023] 4. This application realizes a passive large-angle scanning OPA, and on this basis, it still has high scalability, such as increasing the number of OPA channels, increasing the extension line length, and further reducing the waveguide spacing, thereby improving the OPA's resolution, scanning angle, and suppression of sidelobe generation. And this solution can also be applied to other platforms, such as SOI, GaAs and other substrates.
[0024] 5. This application achieves passivity, and the passive optical phased array will not generate additional heat due to the operation of electronic components during operation, thereby avoiding the impact of heat accumulation on system performance. In high-precision optical applications, thermal effects often cause light beam deviation or signal attenuation. The passive design does not require expensive drive electronics and power management systems, which can significantly reduce system costs, and is especially suitable for large-scale integrated applications. Combining silicon nitride materials and passive phased array technology, the overall system has more obvious advantages in optical performance, reliability, power consumption, cost, etc. For applications that require precise control, low power consumption, and long-term stability (such as satellite communications, lidar, medical imaging, etc.), the passive large field of view silicon nitride optical phased array is a very promising choice.
[0025] 6. This application opens up a new path for the passive application of silicon-based optoelectronic devices. Silicon-based optoelectronics can use integrated optical components to realize functions such as optical waveguides, interferometers, and phase modulation, thereby expanding its boundaries in optical applications. This fusion not only allows silicon-based optoelectronics to gain advantages in traditional optical fields (such as lasers, fiber-optic communications, etc.), but also enables silicon-based platforms to challenge more optical applications and improve the performance and functionality of the overall system.
[0026] 7. The high refractive index and good optical properties of silicon nitride materials, combined with the mature process of silicon-based optoelectronics, can promote the integration of more optical components onto a single silicon-based platform. This integration can not only reduce system complexity and improve stability, but also significantly reduce volume and weight. Silicon-based optoelectronic devices may further develop towards miniaturization, low power consumption, and high integration, and be applied to a wider range of fields, such as mobile communications, unmanned driving, smart sensors, etc.
[0027] In summary, the present application utilizes waveguide extension lines to achieve passive phase changes, and by calculating the extension line length of each waveguide, the same phase difference is achieved between each adjacent waveguide. The present application introduces sinusoidal waveguides, which achieves low crosstalk between waveguides even below the wavelength spacing, thereby achieving large-angle scanning of the OPA and reducing the generation of side lobes. Passive large-field-of-view optical phased arrays can promote the development of integrated, low-power, and high-efficiency silicon-based optoelectronic devices, and also provide new technical paths for multiple cutting-edge technology fields such as optical communications, optical sensing, lidar, and quantum optics. This will accelerate the development of silicon-based optoelectronics towards higher performance and wider applications, opening up more possibilities. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.
[0029] Figure 1 A top view of a passive large field of view silicon-based optical phased array in one embodiment;
[0030] Figure 2 A layered structure diagram of a passive large field of view silicon-based optical phased array in one embodiment;
[0031] Figure 3 A waveguide grating structure diagram of a passive large field of view silicon-based optical phased array in one embodiment;
[0032] Figure 4FIG. 1 is a diagram of an inverted cone coupled waveguide structure of a passive large field of view silicon-based optical phased array in one embodiment.
[0033] 1. Optical beam splitting module; 2. Phase delay module; 21. X-shaped waveguide array; 22. Sinusoidal waveguide array; 3. Waveguide grating antenna module; 4. Silicon nitride layer; 5. Silicon dioxide buried oxide layer; 6. Silicon substrate; 7. Waveguide grating; 8. Inverted cone coupled waveguide; 81. Gradient zone; 82. Stable zone.
[0034] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0035] The following part will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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.
[0036] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.
[0037] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, "and / or" in the full text includes three solutions. Taking A and / or B as an example, it includes technical solution A, technical solution B, and technical solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.
[0038] refer to Figure 1 and Figure 2The present application provides a passive large-field-of-view silicon-based optical phased array, which includes a silicon substrate 6, a silicon dioxide buried oxide layer 5 and a silicon nitride layer 4, wherein the silicon dioxide buried oxide layer 5 is arranged on the upper surface of the silicon substrate 6; the silicon nitride layer 4 is arranged on the upper surface of the silicon dioxide buried oxide layer 5; the height of the silicon substrate 6 is greater than the height of the silicon dioxide buried oxide layer 5, and the height of the silicon dioxide buried oxide layer 5 is greater than the height of the silicon nitride layer 4.
[0039] In this embodiment, the height of the silicon substrate 6 is 500 μm, the height of the silicon dioxide buried oxide layer 5 is 2 μm, the material of all components in the silicon nitride layer 4 is silicon nitride, and the height of the waveguide structure in the silicon nitride is consistent. The height of each component of the silicon nitride layer 4 is 0.5 μm.
[0040] refer to Figure 1 and Figure 4 The silicon nitride layer 4 includes an inverted cone coupling waveguide 8, an optical splitting module 1, a phase delay module 2 and a waveguide grating antenna module 3. The inverted cone coupling waveguide 8 is used to couple the input light into the optical splitting module 1. The optical splitting module 1 is used to divide the optical signal generated by the input light into N equal-power sub-optical signals. The phase delay module 2 includes a figure-shaped waveguide array 21 and a sinusoidal waveguide array 22. The figure-shaped waveguide array 21 is used to perform phase control on each sub-optical signal so that any two adjacent sub-optical signals have the same phase difference. The sinusoidal waveguide array 22 is used to reduce the waveguide spacing. The waveguide grating antenna module 3 is used to radiate the light energy output by the sinusoidal waveguide array 22, and N is greater than or equal to 2.
[0041] In this embodiment, N is 128.
[0042] The optical signal generated by the external laser source is coupled into the optical splitting module 1 through the inverted cone coupling waveguide 8. After passing through the optical splitting module 1, the power is equally divided into 128 paths, and 128 sub-optical signals of equal power are obtained, which are transmitted to the phase delay module 2. The "X"-shaped waveguide array 21 performs phase control on each sub-optical signal, so that any two adjacent sub-optical signals have the same phase difference. Then the sub-optical signals are transmitted to the sinusoidal waveguide array 22 via the "X"-shaped waveguide array 21, thereby reducing the waveguide spacing of each path to achieve large-angle scanning, and finally radiate the light energy into space through the waveguide grating antenna module 3 to achieve two-dimensional scanning.
[0043] The present application divides the input light into 128 coherent light beams through the optical beam splitting module 1, and then introduces a phase difference through each branch of the sine waveguide array 21, realizes narrow spacing and low crosstalk between waveguides in the sinusoidal waveguide array 22, and finally radiates the light of the optical phased array into space through the waveguide grating antenna module 3. The optical phased array of the present application does not need to use electrical or thermal adjustment to change the phase, and after passing through the compactly arranged sinusoidal waveguide array 22, a large field of view scanning of the optical phased array can be realized.
[0044] refer to Figure 4 The inverted cone coupling waveguide 8 includes a gradient zone 81 and a stable zone 82. The end of the gradient zone 81 away from the stable zone 82 is the input end. The size of the gradient zone 81 gradually increases from the input end to the end of the gradient zone 81 close to the stable zone 82 until it becomes the same as the size of the stable zone 82.
[0045] In this embodiment, the inverted tapered coupler is designed based on an input light of 1550 nm, and the waveguide size at the input end is 500 nm wide, passes through a 4000 nm gradient zone 81, and then expands to 1000 nm width, the same as the bus waveguide.
[0046] Specifically, the input light used in the present application is a tunable narrow-linewidth laser with a tuning range of 1500-1600nm and a linewidth of 80kHz.
[0047] refer to Figure 1 The structure of the silicon nitride layer 4 is shown in the figure. The silicon nitride layer 4 also includes a plurality of silicon nitride waveguides, wherein the optical splitting module 1, the phase delay module 2 and the waveguide grating antenna module 3 are interconnected through the silicon nitride waveguide to achieve low-loss optical interconnection between different modules.
[0048] The optical beam splitting module 1 is composed of a plurality of cascaded multi-mode interference couplers, and the input light is split into 128 paths through the plurality of cascaded interference couplers.
[0049] Specifically, the cascaded multimode coupler divides the power of the optical signal into two. The input is a rectangular silicon nitride waveguide, the middle multimode interference coupling region is a larger rectangular silicon nitride waveguide, and the output is two rectangular silicon nitride waveguides of the same size as the input, where the length of the rectangular silicon nitride waveguide is 20 to 28 μm.
[0050] In this embodiment, the optical splitting module 1 includes an input waveguide, 28 one-to-two MMIs, and 7 groups of output waveguides. The first group has 2 output waveguides, the second group has four output waveguides, the third group has 8 output waveguides, the fourth group has 16 output waveguides, the fifth group has 32 output waveguides, the sixth group has 64 output waveguides, and the seventh group has 128 output waveguides.
[0051] Specifically, the optical splitting module 1 is a cascade of several multimode interference couplers (MMI), which successfully divides the input optical power evenly into 128 branches. MMI uses the principle of multimode interference to achieve efficient coupling and distribution of optical signals through precise geometric design and mode control. When the optical signal enters the interference coupler through a multimode waveguide, the different modes in the waveguide will couple and interfere with each other. By designing a specific geometric shape and waveguide size, light of a specific mode can interfere constructively or destructively at different time and space positions, thereby achieving the purpose of signal distribution or synthesis.
[0052] The X-shaped waveguide array 21 includes 128 waveguides, wherein N waveguides have different lengths. Specifically, 127 waveguides are X-shaped waveguides, and the bottom waveguide in the X-shaped waveguide array 21 is a straight waveguide.
[0053] The sinusoidal waveguide array 22 includes 128 sinusoidal waveguides, wherein the distance between any two adjacent sinusoidal waveguides is less than the wavelength of the input light. Specifically, a sinusoidal waveguide refers to a waveguide whose shape or path presents a sinusoidal wave curve in the design of the waveguide.
[0054] Specifically, the input light passes through the X-shaped waveguide array 21, and after calculation, each branch introduces the same phase difference, and then passes through the sinusoidal waveguide array 22. The sinusoidal waveguide array 22 arranges the waveguides compactly, and the waveguide spacing directly affects the scanning angle. Specifically, a waveguide array with a larger spacing will result in a smaller scanning angle, while a smaller waveguide spacing can achieve a larger scanning angle. Through the sinusoidal waveguide array 22, based on the waveguide refractive index distribution principle, the sinusoidal waveguide array 22 can reduce the waveguide spacing while achieving low crosstalk of the waveguide components and reducing the generation of side lobes.
[0055] According to the calculated phase difference required for each branch, the length of the "J"-shaped waveguide is designed to achieve the same phase difference between each adjacent waveguide. Specifically, after determining the phase difference of each adjacent branch, the length of each branch is designed according to the following formula.
[0056] The lateral scanning angle of OPA satisfies the following formula:
[0057] sinθ=λΔφ / 2πd
[0058] Δφ=2πn eff ΔL / λ-2mπ
[0059] θ is the lateral scanning angle of the OPA, λ is the wavelength of the incident light in vacuum, Δφ is the phase difference between adjacent channels, and d is the spacing of the zigzag waveguide. effis the effective refractive index of the X-shaped waveguide at λ, ΔL is the path difference, and m is an integer. When ΔL increases sequentially, Δφ also changes, thereby changing the lateral scanning angle of the OPA. Therefore, the lateral scanning of the OPA is achieved under passive conditions.
[0060] According to the above formula, when λ remains unchanged, the ratio of Δφ / d determines the size of θ. Therefore, after using the "J"-shaped waveguide to determine Δφ, the size of d is particularly important. However, the reduction in waveguide spacing will cause crosstalk between waveguides. When light is injected into one of the waveguides, it will excite the symmetric and antisymmetric supermodes supported by the structure. When the two waveguides are too close, the supermode constant will not be 0, resulting in periodic transmission of optical power between the waveguides, causing mode leakage between the waveguides, resulting in a decrease in light transmittance. Therefore, we use Δβ bent The difference in (sinusoidal waveguide supermode propagation constant) is set to zero to effectively suppress power exchange between waveguides. bent According to the following formula, we can get
[0061] Δβ bent =ΔβJ 0 4π 2 (W+G)n eff A / Pλ 0
[0062] Among them J 0 is the zero-order Bessel function, Δβ is the supermodular constant difference, W is the width of the sinusoidal waveguide, G is the width of the gap between the two sinusoidal waveguides, A is the amplitude of the sinusoidal waveguide, and P is the period length of the sinusoidal waveguide. For the first zero point of the Bessel function, we can get the optimal amplitude A that can bend Δβ to zero opt .
[0063] A opt =2.405λP / 4π 2 (W+G)n eff
[0064] After determining the waveguide width, waveguide height, waveguide spacing and other parameters, the amplitude A of the sinusoidal waveguide can be obtained, so that the crosstalk between waveguides is reduced to a very low level. This application uses a silicon nitride sinusoidal waveguide with a width of 1000nm, a sinusoidal waveguide gap spacing of 275nm, a period of 10μm, and a sinusoidal waveguide thickness of 500nm, so the resulting A is 1.056μm.
[0065] refer to Figure 3 The waveguide grating antenna module 3 includes N waveguide gratings 7. Specifically, the waveguide grating 7 is arranged according to the sinusoidal waveguide array 22, so as to have a higher emissivity. The grating period of the grating is different, so the scanning range and the divergence angle are different. Among them, the grating duty cycle of the waveguide grating 7 is 0.5, and the grating period is 1 μm.
[0066] The working principle of the present application is as follows: an external light source is directly coupled into the optical splitting module 1 through the input end face of the inverted tapered coupling waveguide 8, and the input light is divided into 128 paths by cascading multiple MMIs. The 128 paths have the same optical power and phase. The "J"-shaped waveguide array is used to make each adjacent waveguide have the same phase difference, and then the light is input into the sinusoidal waveguide array, thereby reducing the waveguide spacing of each path to achieve large-angle scanning, and finally radiating the light energy into space through the waveguide grating 7 to achieve two-dimensional scanning.
[0067] Compared with the prior art, the passive large field of view silicon-based optical phased array of the present application has the following advantages:
[0068] (1) The optical phased array of the present application does not generate additional heat due to the operation of electronic components during operation, thereby avoiding the impact of heat accumulation on system performance. The passive design does not require expensive drive electronics and power management systems, which can significantly reduce system costs and is particularly suitable for large-scale integrated applications. Combining silicon nitride materials and passive phased array technology, the overall system has more obvious advantages in optical performance, reliability, power consumption, cost, etc.
[0069] (2) The system is integrated on a silicon nitride chip, which is easy to mass-produce in actual production and has the advantages of small size, high flexibility, simple structure, and easy compatibility with other systems.
[0070] (3) The sinusoidal waveguide structure shortens the waveguide spacing to less than the wavelength length, which not only greatly improves the scanning angle but also suppresses the side lobes to a certain extent.
[0071] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.
Claims
1. A passive large field of view silicon-based optical phased array, characterized in that: include: Silicon substrate; A silicon dioxide buried oxide layer, wherein the silicon dioxide buried oxide layer is disposed on the upper surface of the silicon substrate; A silicon nitride layer, wherein the silicon nitride layer is arranged on the upper surface of the silicon dioxide buried oxide layer; the silicon nitride layer includes an inverted cone coupling waveguide, an optical beam splitting module, a phase delay module and a waveguide grating antenna module, wherein the inverted cone coupling waveguide is used to couple input light to the optical beam splitting module, the optical beam splitting module is used to equally split the optical signal generated by the input light into N equal-power sub-optical signals, the phase delay module includes a figure-of-feet waveguide array and a sinusoidal waveguide array, the figure-of-feet waveguide array is used to perform phase control on each sub-optical signal, so that any two adjacent sub-optical signals have the same phase difference, the sinusoidal waveguide array is used to reduce the waveguide spacing, and the waveguide grating antenna module is used to radiate the light energy output by the sinusoidal waveguide array, and N is greater than or equal to 2.
2. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The optical beam splitting module includes a plurality of cascaded multi-mode interference couplers.
3. The passive large field of view silicon-based optical phased array according to claim 2, characterized in that: The cascaded multimode coupler divides the power of the optical signal into two. The input is a rectangular silicon nitride waveguide, the middle multimode interference coupling region is a larger rectangular silicon nitride waveguide, and the output is two rectangular silicon nitride waveguides of the same size as the input, wherein the length of the rectangular silicon nitride waveguide is 20 to 28 μm.
4. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The X-shaped waveguide array includes N waveguides, wherein the lengths of the N waveguides are different.
5. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The sinusoidal waveguide array includes N sinusoidal waveguides, wherein the distance between any two adjacent sinusoidal waveguides is less than the wavelength of the input light.
6. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The waveguide grating antenna module includes N waveguide gratings.
7. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The optical beam splitting module, the phase delay module and the waveguide grating antenna module are interconnected through a silicon nitride waveguide to achieve low-loss optical interconnection between different modules.
8. The passive large field of view silicon-based optical phased array according to claim 7, characterized in that: The width of the silicon nitride waveguide ranges from 800nm to 1000nm.
9. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The height of the silicon substrate is greater than the height of the silicon dioxide buried oxide layer, and the height of the silicon dioxide buried oxide layer is greater than the height of the silicon nitride layer.
10. The passive large field of view silicon-based optical phased array according to claim 1, characterized in that: The inverted cone coupling waveguide comprises a gradual change zone and a stable zone, wherein an end of the gradual change zone away from the stable zone is an input end, and a size of the gradual change zone from the input end to an end of the gradual change zone close to the stable zone gradually increases until it becomes the same as a size of the stable zone.