High saturation photodetector based on metasurface homogenization

Abstract

The application relates to the fields of photoelectric detection and microwave photon technology, in particular to a high-saturation photoelectric detector based on super surface uniform light, which comprises a super surface structure layer, which is used for phase modulation of an incident light beam to obtain a focused and uniformly lighted light beam; a substrate layer, which is translucent at a communication wave band (such as 1310 nm or 1550 nm) and is located above the super surface structure layer to receive and spread the focused and uniformly lighted light spot to form uniformly distributed light spots; an absorption layer, which is located above the substrate layer to absorb the uniformly distributed light spots and generate photo-generated carriers; and a photoelectric detector structure layer, which is located above the absorption layer to collect the photo-generated carriers and output corresponding electric signals. Therefore, the problems of local oversaturation and serious thermal effects caused by uneven distribution of Gaussian light beams are solved.

Description

Technical Field

[0001] This invention relates to the fields of photoelectric detection and microwave photonics technology, and in particular to a high-saturation photodetector based on metasurface uniform light. Background Technology

[0002] High-saturation photodetectors are core components in optical communication and microwave photonics systems. To maintain linear response and avoid device damage under high incident light power, existing mesa-type high-saturation photodetectors typically reduce carrier density and suppress space charge effects by increasing the active region diameter (typically 20 μm to 30 μm), thereby improving saturation output power.

[0003] In practical applications, high-saturation photodetectors typically receive optical signals via fiber coupling. Common fiber coupling methods include tapered fiber coupling. The output beam of a tapered fiber is usually a Gaussian beam, with its intensity distribution following a Gaussian function, reaching its maximum intensity at the center and rapidly attenuating towards the edges. A typical Gaussian beam spot diameter (1 / e²) is comparable to the fiber mode field diameter, approximately 10 μm.

[0004] Metasurfaces, as two-dimensional planar optical elements composed of subwavelength structural units, can precisely control the complex amplitude (phase and amplitude) of transmitted light by adjusting the geometric parameters of the microstructure, showing great integration potential in fields such as beam shaping and holographic imaging.

[0005] However, existing technologies for coupling high-saturation photodetectors with optical fibers have the following main drawbacks: (1) Uneven light intensity distribution leads to premature local saturation: The light intensity at the center of the Gaussian beam output from the tapered fiber is much higher than that at the edge. When this Gaussian beam is directly coupled to the active region of a high-saturation photodetector with a diameter of 20~30μm, the optical power is concentrated in the central region of the detector, resulting in an excessively high carrier density in the central region and premature saturation. Although the overall active region area of ​​the detector is small, the actual effective saturated optical power is far lower than the theoretical value due to the extremely uneven distribution of optical power, which severely limits the overall effective saturated optical power and linear dynamic range.

[0006] (2) Low efficiency of light field utilization: Due to excessive energy concentration in the center, the edge region of the 20~30μm absorption area is not fully utilized, and the effective area actually participating in photoelectric conversion is much smaller than the physical design area.

[0007] (3) Existing homogenization schemes (such as microlens arrays, integrating bars, or refractive DOEs) can be integrated at the system level, but they have the following limitations: Volume redundancy: The physical thickness of these components is relatively large, making it difficult to further miniaturize the package size.

[0008] Strict alignment tolerances: Multi-element cascading (discrete component assembly) introduces complex alignment errors.

[0009] Limited functionality: Existing solutions often only achieve a single homogenization or focusing function. For example, integrating a microlens on the back can only achieve focusing, not homogenization. Traditional optical elements lack the ability to simultaneously and precisely control phase and amplitude (complex amplitude modulation) at the subwavelength scale. Summary of the Invention

[0010] This invention provides a high-saturation photodetector based on metasurface uniform light distribution to solve problems such as local oversaturation and severe thermal effects caused by uneven Gaussian beam distribution.

[0011] A first aspect of the present invention provides a high-saturation photodetector based on metasurface homogenization, comprising: Metasurface structure layer is used to phase modulate the incident beam to obtain a focused and homogenized beam; A substrate layer, which is a semi-transparent substrate for communication bands, is located above the metasurface structure layer to receive and propagate the focused and homogenized light spot to form a uniformly distributed light spot. An absorption layer, located above the substrate layer, is provided to absorb the uniformly distributed light spot and generate photogenerated carriers. A photodetector structure layer is located above the absorption layer to collect the photogenerated carriers and output corresponding electrical signals.

[0012] Optionally, the metasurface structure layer is composed of multiple subwavelength-scale microstructure units arranged together.

[0013] Optionally, the microstructure unit of the metasurface structure layer adopts at least one of cylindrical nanopillars, rectangular nanopillars, nanofins, H-shaped structures, ring structures, or cross-shaped structures.

[0014] Optionally, the phase distribution of the metasurface structure layer is determined by reverse design or phase gradient method.

[0015] Optionally, the overall diameter of the metasurface structure layer is 30 μm to 100 μm.

[0016] Optionally, the thickness of the substrate layer is 80~325μm, the thickness of the absorption layer is 0.5~5μm, and the diameter of the active region of the photodetector structure layer is 20~30μm.

[0017] Optionally, the substrate material is indium phosphide (InP), silicon dioxide (SiO2), or silicon nitride (SiN). x Any one of them.

[0018] Optionally, the photodetector structure layer may employ any one of a PIN photodiode, avalanche photodiode, unit traveling wave carrier photodiode, or metal-semiconductor-metal photodetector.

[0019] A second aspect of the present invention provides a phase distribution design method for a high-saturation photodetector based on metasurface homogenization, comprising the following steps: A light transmission model is established from the exit surface of the metasurface structure layer to the absorption layer to simulate the actual light field distribution of the incident light beam after passing through the metasurface structure layer, propagating in the substrate layer, and reaching the absorption layer. The target light field is defined as a focused light spot with uniform light intensity distribution within a circular area of ​​a preset diameter at the location of the absorption layer; Using the phase delay of the metasurface structure layer as the optimization variable and the deviation between the target optical field and the actual optical field distribution as the cost function, global optimization is performed using the reverse design method or the phase gradient method to obtain the optimized continuous phase distribution. The optimized continuous phase distribution is discretized into geometric parameters of metasurface microstructure units to determine the phase distribution.

[0020] Optionally, the reverse design method may be any one of gradient descent, genetic algorithm, particle swarm optimization algorithm, or deep learning-assisted optimization method.

[0021] The high-saturation photodetector based on metasurface homogenization proposed in this invention achieves a flat-top uniform distribution of the Gaussian beam after it passes through the substrate and reaches the absorption region by directly integrating a metasurface homogenization structure on the back side of an InP substrate, thereby significantly improving the saturated output power and linear operating range of the photodetector. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 A block diagram illustrating a high-saturation photodetector based on metasurface uniform light distribution according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the overall structure of a high-saturation photodetector based on metasurface uniform light distribution according to an embodiment of the present invention; Figure 3This is a schematic diagram of the geometric parameters of a microstructure unit of a metasurface structure layer provided according to an embodiment of the present invention, wherein (a) is a cylindrical nanopillar and (b) is a rectangular nanopillar; Figure 4 This is a top view schematic diagram of a metasurface structure layer provided according to an embodiment of the present invention; Figure 5 The above are simulation comparison diagrams of the light field distribution of a metasurface with uniform light distribution provided by an embodiment of the present invention. (a) is the incident 5µm waist Gaussian beam and its central one-dimensional field distribution diagram, (b) is the light field distribution (Gaussian distribution) at the absorption layer without a metasurface and its central one-dimensional field distribution diagram, and (c) is the light field distribution (uniform distribution) at the absorption layer with a uniform light metasurface and its central one-dimensional field distribution diagram.

[0023] Explanation of reference numerals in the attached figures: 100 - High-saturation photodetector based on metasurface uniform light, 101 - Metasurface structure layer, 102 - Substrate layer, 103 - Absorption layer, 104 - Photodetector structure layer. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] The following describes an embodiment of the present invention, a high-saturation photodetector based on metasurface homogenization, with reference to the accompanying drawings.

[0026] Figure 1 This is a block diagram of a high-saturation photodetector based on metasurface uniform light, provided as an embodiment of the present invention.

[0027] like Figure 1 As shown, the high-saturation photodetector 100 based on metasurface uniform light includes: a metasurface structure layer 101, a substrate layer 102, an absorption layer 103, and a photodetector structure layer 104.

[0028] The metasurface structure layer 101 is used to phase modulate the incident beam to obtain a focused and homogenized beam. The substrate layer 102, a semi-transparent substrate for the communication band, is located above the metasurface structure layer 101. A dielectric buffer layer is provided between the metasurface structure layer and the back of the substrate layer to receive and propagate the focused and homogenized light spot, forming a uniformly distributed light spot. The substrate layer 102 can be indium phosphide (InP), silicon dioxide (SiO2), or silicon nitride (SiN). xAny one of the following. The absorption layer 103 is located above the substrate layer 102 to absorb a uniformly distributed light spot and generate photogenerated carriers. The photodetector structure layer 104 is located above the absorption layer 103 to collect the photogenerated carriers and output a corresponding electrical signal.

[0029] In some embodiments, the metasurface structure layer is composed of a plurality of subwavelength-scale microstructural units arranged together.

[0030] Specifically, such as Figure 2 As shown, in this embodiment of the invention, the metasurface structure layer is located on the back side of the substrate (i.e., the side away from the photodetector structure) and is composed of periodically or non-periodically arranged subwavelength-scale microstructure units. This metasurface structure layer is directly fabricated on the back side of an 80-150 μm InP substrate, or it can be selectively etched to make the InP epitaxial layer of the detector only 2 μm-10 μm thick, and then heterobonded to a 150 μm-325 μm thick SiO2 or SiN substrate. x On the substrate. The overall diameter of the metasurface structure layer is 30 μm to 100 μm, with a typical value of 60 μm.

[0031] In some embodiments, the microstructure units of the metasurface structure layer are at least one of cylindrical nanopillars, rectangular nanopillars, nanofins, H-shaped structures, ring structures, or cross-shaped structures.

[0032] Specifically, such as Figure 3 As shown, the geometric parameters of each microstructure unit in the metasurface structure layer are optimized to achieve precise control over the phase and amplitude of transmitted light. The specific forms of the microstructure units include, but are not limited to, cylindrical nanopillars, rectangular nanopillars, nanofins, and other subwavelength structures (including H-shaped structures, ring structures, cross-shaped structures, etc.). The materials selected for the microstructure units include, but are not limited to: InP (indium phosphide), TiO2 (titanium dioxide), Si (silicon), and SiN. x High refractive index dielectric materials such as silicon nitride, gallium oxide (Ga2O3), and hafnium oxide (HfO2) are used. Preferably, materials with low absorption loss and high refractive index contrast in a preset operating wavelength range (e.g., 1550 nm) are selected.

[0033] Furthermore, when the microstructure unit is a cylindrical nanopillar, the diameter is set to 100~600 nm, the height is set to 500~1200 nm, and the period is set to 300~1000 nm. By changing the diameter of the cylinder, the transmission phase can be used to change the transmission delay of light, so that the substrate layer can obtain a focused and homogenized beam.

[0034] Furthermore, when the microstructure unit uses rectangular nanopillars, the length and width are set to 100~600 nm and 100~600 nm, respectively. By changing the aspect ratio and orientation angle, the phase and polarization can be controlled simultaneously, so that the substrate layer can obtain a focused and homogenized beam.

[0035] Furthermore, when the microstructure unit adopts a columnar structure of nanofins with an elliptical or rectangular cross-section, geometric phase modulation is achieved by rotating the orientation angle, so that the substrate layer can obtain a focused and homogenized beam.

[0036] It should be noted that, in addition to dielectric metasurfaces, metasurface structures can also be made of metallic metasurfaces (such as Au and Ag nanostructures) or hybrid plasmon-dielectric metasurfaces. Metallic metasurfaces achieve phase modulation through surface plasmon resonance, but may introduce additional absorption losses.

[0037] In some embodiments, the phase distribution of the metasurface structure layer is determined by reverse design or phase gradient method.

[0038] Specifically, embodiments of the present invention determine the phase distribution through reverse design or phase gradient methods, incorporating the substrate's refractive index dispersion and diffraction effects into the optimization process to compensate for the influence of substrate propagation on the light field distribution. Taking an InP substrate as an example, the specific steps are as follows: Step 1: Establish an optical transmission model including the InP substrate. The finite-difference time-domain method (FDTD) can be used to establish an optical transmission model from the exit surface of the metasurface structure layer to the absorption layer. This model simulates the actual optical field distribution of the incident beam after passing through the metasurface structure layer, propagating a distance of substrate thickness (100 μm) in the InP substrate, and reaching the absorption layer. The model needs to consider the refractive index dispersion effect and absorption loss of the InP substrate.

[0039] Step 2, define the target light field distribution: At the absorption layer location (approximately 100 μm from the metasurface exit surface), define the target light field as a focused spot with uniform light intensity distribution within a circular region of a preset diameter (e.g., 20 μm). Figure 4 As shown.

[0040] The objective function can be expressed as: forming a flat-top beam with a diameter of 20 μm at a distance of d = 100 μm from the metasurface, and the uniformity of light intensity within the beam is better than 90%.

[0041] Step 3: Optimize the metasurface phase distribution: Using the phase delay of each microstructure unit in the metasurface structure layer as the optimization variable and the deviation between the target optical field and the actual optical field distribution as the cost function, global optimization is performed using either inverse design or the phase gradient method to obtain the optimized continuous phase distribution. The inverse design method can be any one of the following: gradient descent, genetic algorithm, particle swarm optimization, or deep learning-assisted optimization.

[0042] It should be noted that the optimization process must simultaneously consider: focusing constraint (to concentrate the light spot within an absorption region with a diameter of 20 μm) and uniform light constraint (to ensure uniform light intensity distribution within the region).

[0043] Step 4: Discretize the optimized continuous phase distribution into geometric parameters of the metasurface microstructure unit: Based on the required phase delay value at each position in the optimized continuous phase distribution, select the corresponding microstructure unit parameters from the pre-established geometric parameter-phase delay lookup table, and then determine the phase distribution.

[0044] It is understood that the phase distribution design method proposed in this embodiment of the invention is applicable to different operating wavelengths, including but not limited to the communication O-band (1310 nm), C-band (1550 nm), L-band (1625 nm), and visible light band (such as 850 nm). However, the geometric parameters of the metasurface need to be re-optimized for different wavelengths.

[0045] It should be noted that, in the embodiments of the present invention, broadband uniform light function can also be achieved by using multi-level metasurfaces or by cascading metasurfaces with diffractive optical elements, so that the detector maintains a uniform optical power distribution over a wide wavelength range.

[0046] In some embodiments, the thickness of the substrate layer is 80~325μm, the thickness of the absorption layer is 0.5~5μm, and the diameter of the active region of the photodetector structure layer is 20~30μm.

[0047] Specifically, the substrate layer can be InP with a thickness of 80~150μm, preferably 100μm. The InP substrate layer is a semi-transparent substrate with high transmittance in the communication band (such as 1310 nm or 1550 nm). The light beam is incident from the back of the substrate, passes through the substrate, and reaches the absorption layer.

[0048] It should be noted that the thickness of the InP substrate layer depends on the thinning process. Besides InP substrates, other III-V group semiconductor substrates can also be used in embodiments of the present invention, such as GaAs (gallium arsenide) substrates, InP / InGaAsP heterostructures, etc. For heterogeneous integration schemes, the substrate material can be SiO2 or SiN. x Correspondingly, the absorber layer material must also match the lattice constant of the substrate.

[0049] Furthermore, the absorber layer is located above the substrate layer and is made of III-V compound semiconductor materials such as InGaAs, with a thickness of 0.1~1μm, preferably 0.5~1μm.

[0050] Furthermore, the photodetector structure layer is located above the absorption layer and includes an upper electrode and a lower electrode. Its active region diameter is 20~30μm, preferably 20μm. Specific implementations of the photodetector structure include, but are not limited to, PIN photodiode structure, avalanche photodiode (APD) structure, unit traveling wave carrier photodiode, or metal-semiconductor-metal (MSM) structure.

[0051] Among them, the PIN photodiode includes a P-type contact layer, an intrinsic absorption layer (InGaAs), and an N-type contact layer, with the P-type and N-type contact layers led out through the upper and lower electrodes, respectively; the improved UTC (unit traveling wave carrier) photodiode adopts a gradient-doped absorption and collection layer design to improve the response speed and saturation power; the MSM photodetector adopts an interdigitated electrode structure with an electrode spacing of 0.5~2μm and an active region diameter of 20~30μm.

[0052] It should be noted that the photodetector structure layer can adopt a waveguide-integrated photodetector design, which couples the metasurface uniform light structure with the waveguide to realize on-chip optical interconnect applications.

[0053] The fabrication process of the high-saturation photodetector based on metasurface homogenization proposed in this embodiment of the invention is described below, taking an InP substrate as an example. Step 1: On the front (top) surface of the InP substrate, the absorption layer (InGaAs) and the various layers of the photodetector (such as P-type layer, N-type layer, etc.) are grown sequentially by epitaxial growth (such as MOCVD or MBE) to obtain the first device.

[0054] Step 2: The photodetector mesa structure is fabricated on the first device using photolithography and etching processes, and the active region diameter is defined as 20~30μm to obtain the second device.

[0055] Step 3: Deposit and pattern a metal electrode (such as Ti / Pt / Au) on the second device to form an upper electrode and lower electrode contact, thus obtaining the third device.

[0056] Step four: The InP substrate in the third device is thinned to 80~150μm (preferably 100μm), and the back side of the substrate is flattened by chemical mechanical polishing (CMP) to obtain the fourth device.

[0057] Step 5: Fabricate a metasurface structure layer on the back side of the substrate of the fourth device: First, deposit a dielectric material layer (such as TiO2, SiN).x Then, using electron beam lithography (EBL) or deep ultraviolet lithography (DUV) combined with reactive ion etching (RIE) or inductively coupled plasma etching (ICP), subwavelength microstructure arrays are etched onto the dielectric layer. An anti-reflective coating (such as SiO2 or SiN) can also be deposited on the surface of the metasurface structure layer. x This is to further reduce interface reflection loss.

[0058] It should be noted that if a heterogeneous integration scheme is adopted, during the fabrication process, selective etching of the sacrificial layer can be used to make the InP epitaxial layer of the detector only 2μm~10μm thick, and then heterobonded onto a 150um~325um thick SiO2 or SiN layer. x The substrate is then deposited with a corresponding metasurface material, followed by etching. The large refractive index difference between the SiO2 substrate and the metasurface nanopillar material makes it easier to control the light field.

[0059] The working process of the high-saturation photodetector based on metasurface homogenization proposed in this embodiment of the invention is described below, taking an InP substrate as an example. The specific process is as follows: A Gaussian beam output from a tapered fiber is incident from the back side of an InP substrate onto a metasurface structure layer.

[0060] The metasurface structure layer modulates the phase of the incident beam, enabling the light to propagate to the absorption region and achieve a homogenization function. The beam, after being focused and homogenized by the metasurface modulation, enters the InP substrate layer.

[0061] After focusing and homogenization, the beam propagates approximately 100 μm in the InP substrate. During this process, the phase distribution of the metasurface design has been pre-compensated for the substrate propagation effect, ensuring that the beam forms a uniformly distributed spot upon reaching the absorption layer.

[0062] A uniformly distributed light spot illuminates the absorption layer, with the spot diameter matching the active region diameter of the detector (20 μm), and the optical power is uniformly distributed within the active region.

[0063] The absorption layer (InGaAs) absorbs photons to generate photogenerated carriers, and the photodetector structure layer collects these carriers and outputs an electrical signal. For example... Figure 5 As shown, since the optical power is uniformly distributed in the active region, local oversaturation is avoided, which effectively improves the saturation optical power and linear response range of the detector.

[0064] In summary, the high-saturation photodetector based on metasurface homogenization proposed in the embodiments of the present invention has the following beneficial effects: (1) Significantly improve effective saturated optical power: By shaping the Gaussian beam into a uniformly distributed flat-top spot through the metasurface homogenization structure, the optical power is uniformly distributed in the active region of the detector, eliminating the local oversaturation phenomenon in the central region. Compared with the traditional scheme without homogenization structure, the effective saturated optical power can be increased by 2 to 5 times (the specific increase depends on the homogenization quality of the metasurface).

[0065] (2) Extended linear response range: Due to the uniform distribution of optical power, the carrier density of the detector tends to be consistent throughout the active region, avoiding nonlinear effects caused by excessively high local carrier density. This allows the detector to maintain a linear response over a wider range of incident optical power, thus improving the dynamic range of the detector.

[0066] (3) Monolithic integration is achieved, resulting in small size and light weight: The metasurface is directly integrated on the back side of the substrate, eliminating the need for additional discrete optical components and realizing monolithic integration of light homogenization function and photodetector. Compared with traditional microlens arrays or integrating rod schemes, the scheme of this invention has significant miniaturization advantages, which is beneficial for realizing high-density photodetector arrays.

[0067] (4) Precise compensation for substrate propagation effect: The phase distribution design of the metasurface fully considers the light propagation characteristics of the 100μm thick substrate, pre-compensates the diffraction and aberration effects introduced by the substrate, and ensures the formation of a high-quality uniform light spot at the absorption layer position.

[0068] (5) Flexible design and wide applicability: The reverse design method of metasurface can be flexibly optimized according to different incident beam parameters (such as spot size, wavelength, etc.) and target spot parameters (such as diameter, uniformity, etc.), and is suitable for various photodetector structures and application scenarios, especially for high-speed optical communication (such as 1550 nm communication band), millimeter wave and terahertz photonic links and other application scenarios that require high saturation optical power detection.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0072] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0073] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0074] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0075] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0076] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A highly saturated photodetector based on metasurface uniform light distribution, characterized in that, include: Metasurface structure layer is used to phase modulate the incident beam to obtain a focused and homogenized beam; A substrate layer, which is a semi-transparent substrate for communication bands, is located above the metasurface structure layer to receive and propagate the focused and homogenized light spot to form a uniformly distributed light spot. An absorption layer, located above the substrate layer, is provided to absorb the uniformly distributed light spot and generate photogenerated carriers. A photodetector structure layer is located above the absorption layer to collect the photogenerated carriers and output corresponding electrical signals.

2. The high-saturation photodetector based on metasurface uniform light as described in claim 1, characterized in that, The metasurface structure layer is composed of multiple subwavelength-scale microstructural units arranged together.

3. The high-saturation photodetector based on metasurface uniform light as described in claim 2, characterized in that, The microstructure unit of the metasurface structure layer adopts at least one of the following: cylindrical nanopillars, rectangular nanopillars, nanofins, H-shaped structures, ring structures, or cross-shaped structures.

4. The high-saturation photodetector based on metasurface uniform light as described in claim 1, characterized in that, The phase distribution of the metasurface structure layer is determined by reverse design or phase gradient method.

5. The high-saturation photodetector based on metasurface uniform light as described in claim 1, characterized in that, The overall diameter of the metasurface structure layer is 30μm~100μm.

6. The high-saturation photodetector based on metasurface homogenization according to claim 1, characterized in that, The thickness of the substrate layer is 80~325μm, the thickness of the absorption layer is 0.5~5μm, and the diameter of the active region of the photodetector structure layer is 20~30μm.

7. The high-saturation photodetector based on metasurface uniform light as described in claim 1, characterized in that, The substrate material is indium phosphide (InP), silicon dioxide (SiO2), or silicon nitride (SiN). x Any one of them.

8. The high-saturation photodetector based on metasurface uniform light as described in claim 1, characterized in that, The photodetector structure layer adopts any one of the following: PIN photodiode, avalanche photodiode, unit traveling wave carrier photodiode, or metal-semiconductor-metal photodetector.

9. A phase distribution design method for a high-saturation photodetector based on metasurface homogenization, employing the high-saturation photodetector based on metasurface homogenization as described in any one of claims 1-8, characterized in that, Includes the following steps: A light transmission model is established from the exit surface of the metasurface structure layer to the absorption layer to simulate the actual light field distribution of the incident light beam after passing through the metasurface structure layer, propagating in the substrate layer, and reaching the absorption layer. The target light field is defined as a focused light spot with uniform light intensity distribution within a circular area of ​​a preset diameter at the location of the absorption layer; Using the phase delay of the metasurface structure layer as the optimization variable and the deviation between the target optical field and the actual optical field distribution as the cost function, global optimization is performed using the reverse design method or the phase gradient method to obtain the optimized continuous phase distribution. The optimized continuous phase distribution is discretized into geometric parameters of metasurface microstructure units to determine the phase distribution.

10. The phase distribution design method for a high-saturation photodetector based on metasurface uniform light as described in claim 9, characterized in that, The reverse design method can be any one of gradient descent, genetic algorithm, particle swarm optimization algorithm, or deep learning-assisted optimization method.

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