Micro-nano grating and photocathode collaborative design method

Abstract

The application discloses a micro-nano grating and photocathode collaborative design method. The method breaks the traditional isolated design, and considers the micro-nano grating and the photocathode as an organic whole, and takes the spectral response or integral quantum efficiency of the system as a whole as a target function. Specifically, the method comprises the following steps: establishing a system structure model and clearly defining an optimization target and process constraints; establishing a complex refractive index-wavelength correlation model of the photocathode to accurately obtain a complex refractive index distribution; determining a set of parameters to be optimized and setting initial values; calculating the system electric field distribution under the current parameters based on an electromagnetic simulation model; combining the electric field distribution and the photoelectric emission mechanism to calculate the spectral response of the system in the target waveband; and using a parameter optimization algorithm to iteratively search the parameter space, and outputting an optimal parameter combination. The application fully considers the electromagnetic and photoelectric coupling between the two and the actual process constraints, has the advantages of high design accuracy, strong pertinence, good implementability and the like, and can significantly improve the detection sensitivity of a weak light detection device.

Description

Technical Field

[0001] This invention belongs to the field of interdisciplinary technology of photoelectric detection and micro-nano optics, and in particular, it is a method for the collaborative design of micro-nano gratings and photocathodes. Background Technology

[0002] Photocathodes are core components in photomultiplier tubes, image intensifiers, and other low-light detection devices, responsible for converting incident photons into outgoing photoelectrons. Their performance directly affects the device's quantum efficiency, sensitivity, and signal-to-noise ratio. Improving the photoelectric response capability of photocathodes has always been an important research direction in related fields.

[0003] Existing methods for improving the response capability of photocathodes typically include optimizing cathode materials, improving fabrication processes, and introducing micro / nano gratings. Among these, introducing micro / nano grating structures onto the photocathode surface can alter the propagation path of incident light, extend the effective optical path, and enhance light absorption within the photocathode layer, thereby improving the photocathode's response capability. On one hand, structural parameters such as the period, duty cycle, and trench depth of the micro / nano grating affect the absorption characteristics of the photocathode layer; on the other hand, the photocathode's thickness, film quality, and optical properties determine its light absorption and electron emission capabilities. Most existing grating design methods treat the grating as an independent diffraction element, focusing only on its ability to control incident light. Their optimization goals are usually limited to maximizing the diffraction efficiency at a specific wavelength or broadening the grating's operating bandwidth. This isolated design paradigm ignores the influence of the photocathode and often fails to maximize the response capability of the micro / nano grating-photocathode system. Summary of the Invention

[0004] The purpose of this invention is to overcome existing design limitations by proposing a collaborative optimization design method for micro / nano grating-photocathode systems. This method not only considers the influence of the micro / nano grating structure on the photocathode's light absorption rate but also incorporates it into the photocathode's spectral response model, constructing a spectral response evaluation function for the micro / nano grating-photocathode system. Through a design path of "electromagnetic simulation + parameter optimization," the joint optimization of multiple parameters can be achieved.

[0005] The technical solution to achieve the objective of this invention is: a method for the collaborative design of micro / nano gratings and photocathodes, the method comprising:

[0006] Step 1: Establish a structural model of the micro / nano grating-photocathode system, and clarify the optimization objectives, the objects to be optimized, and the process constraints;

[0007] Step 2: Establish a complex refractive index-wavelength correlation model for the photocathode to obtain the complex refractive index distribution of the photocathode in the target wavelength band;

[0008] Step 3: Determine the set of parameters to be optimized, and set the initial values ​​of each parameter in the set of parameters to be optimized;

[0009] Step 4: Based on the electromagnetic simulation model, calculate the electric field distribution of the micro / nano grating-photocathode system under the current parameter combination;

[0010] Step 5: Calculate the spectral response of the micro / nano grating-photocathode system in the target wavelength band based on the electric field distribution within the photocathode layer;

[0011] Step 6: Establish an objective function with the aim of improving the overall spectral response performance of the system in the target band, and use a parameter optimization algorithm to iteratively search the set of parameters to be optimized until the convergence condition is met, and output the optimal parameter combination.

[0012] Further, the optimization objective in step 1 is to improve the spectral response of the photocathode in a specific wavelength band, which is the 380nm-900nm wavelength band or a subset thereof; the object to be optimized is a micro-nano grating-photocathode system, which includes at least an incident light window, a micro-nano grating layer and a photocathode layer arranged sequentially along the incident light propagation direction, wherein the micro-nano grating layer is disposed between the incident light window and the photocathode layer.

[0013] Furthermore, the process constraints mentioned in step 1 are photocathode parameters affected by the actual manufacturing process, specifically including one or more combinations of photocathode thickness, photocathode structural parameters, photoelectron emission depth, and photocathode cutoff wavelength.

[0014] Furthermore, in step 2, the complex refractive index-wavelength correlation model of the photocathode is expressed as:

[0015]

[0016] In the formula, The refractive index of the photocathode is denoted as . Extinction coefficient, The imaginary unit is used to characterize the dynamic changes in the refractive index and extinction coefficient of a photocathode with the wavelength of incident light. Indicates the wavelength of the incident light.

[0017] Furthermore, the set of parameters to be optimized in step 3 is as follows: any subset of, where The grating constant is The ridge width of the grating, The duty cycle of the grating. The groove depth of the grating. The thickness of the photocathode. λ is the wavelength of the incident light.

[0018] Further, in step 4, the electric field distribution of the micro / nano grating-photocathode system is obtained through multi-wavelength scanning simulation calculations on a system model with a given combination of parameters; the electromagnetic simulation model is implemented using any one of the following: rigorous coupled-wave analysis, finite-difference time-domain method, or finite element method; any point within the photocathode layer... The normalized electric field amplitude at point is denoted as .

[0019] Furthermore, in step 5, the spectral response is determined by the quantum efficiency spectrum. or response spectrum Characterization;

[0020] The quantum efficiency spectrum Satisfy the following formula:

[0021]

[0022] In the formula, For photocathode pair with wavelength of The light absorption coefficient, Indicates wavelength as Light in the photocathode layer The probability that the photoelectrons excited at the point of emission will eventually be emitted from the surface of the photocathode. The volume of the photocathode layer;

[0023] The response spectrum pass The transformation is obtained, and the transformation formula is:

[0024] .

[0025] Furthermore, the photocathode has a wavelength of light absorption coefficient Calculate using the following formula:

[0026]

[0027] In the formula, It is Planck's constant. The speed of light in a vacuum. It is the energy corresponding to the cutoff wavelength of the photocathode. It is a constant.

[0028] Furthermore, the wavelength is Light in the photocathode layer The probability that the photoelectrons excited at the point will eventually be emitted from the surface of the photocathode. Calculate using the following formula:

[0029]

[0030] In the formula, P represents the cathode structural parameter, used to reflect the degree of order and photoelectric emission performance of the cathode thin film; when the photocathode is a polycrystalline photocathode with an electron affinity higher than a preset threshold and a long-range disordered and short-range ordered structure, the value is taken as... Otherwise take ; and All of these are constants related to photocathode technology; The thickness of the photocathode; Spatial location point The component in the normal direction of the cathode layer.

[0031] Furthermore, the objective function mentioned in step 6 is the integral of the quantum efficiency spectrum within the target wavelength band, expressed as:

[0032]

[0033] In the formula, , These are the lower and upper limits of the band to be optimized, respectively.

[0034] Furthermore, the iterative search process of the parameter optimization algorithm described in step 6 specifically includes:

[0035] Sampling is performed within the parameter space to be optimized, and a proxy model is established based on the obtained sample parameter set.

[0036] The parameter optimization algorithm is used to select a new set of candidate parameters in the proxy model.

[0037] Repeatedly calculate the spectral response of the micro / nano grating-photocathode system and update the surrogate model until the convergence condition is met and the optimal parameter combination is obtained.

[0038] Furthermore, the parameter optimization algorithm includes at least one of particle swarm optimization algorithm, simulated annealing algorithm, and genetic algorithm.

[0039] Compared with the prior art, the significant advantages of this invention are:

[0040] (1) The present invention regards the micro-nano grating and photocathode as an organic whole, and incorporates their structural parameters (such as grating constant, trench depth, cathode thickness, etc.) into the same design variable space for joint optimization, which can reflect the coupling relationship between the two and achieve synergistic optimization, thereby maximizing the overall response capability of the micro-nano grating-photocathode system.

[0041] (2) This invention directly incorporates the light absorption enhancement effect brought by micro-nano gratings into the spectral response model of photocathode, thereby using the system spectral response instead of grating diffraction efficiency or photocathode absorptivity as the optimization target. This allows the design results to directly reflect the overall photoelectric emission performance of the device in the target wavelength band, and is more directly oriented towards the practical application needs of photocathodes.

[0042] (3) In the design process, this invention introduces process constraints (such as cathode structure parameters, photoelectron emission depth, cutoff wavelength, etc.) that are affected by the manufacturing process, and establishes a complex refractive index-wavelength correlation model for the photocathode. This approach of combining "actual process parameters" with "electromagnetic simulation" can ensure that the simulation model accurately reproduces the semiconductor characteristics of the real physical device and avoids design distortion caused by idealized modeling.

[0043] (4) This invention adopts the design path of "electromagnetic simulation + parameter optimization". By sampling within the parameter space to be optimized and establishing a surrogate model, a new set of candidate parameters is selected based on the surrogate model combined with optimization algorithms such as simulated annealing. This method can significantly reduce the number of times the heavy electromagnetic calculations are repeatedly performed, thereby obtaining the optimal parameters of the micro-nano grating-photocathode system more efficiently and accurately, and providing a practical implementation method for the design of photocathode devices.

[0044] (5) The optimal parameter set obtained through this collaborative design method (such as the parameter combination in the specific implementation) can significantly improve the quantum efficiency of the micro / nano grating-photocathode system in the target wavelength band compared to the structure without grating or the structure with initial parameters. This is of great significance for enhancing the sensitivity and signal-to-noise ratio of core weak light detection devices such as super-second generation image intensifiers.

[0045] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0046] Figure 1 This is a flowchart of the co-design method for micro / nano gratings and photocathodes according to the present invention.

[0047] Figure 2 This is a schematic diagram of a micro-nano grating-photocathode system in one embodiment.

[0048] Figure 3 This is a schematic diagram of the complex refractive index-wavelength correlation model of a photocathode in one embodiment.

[0049] Figure 4 This is a response spectrum of the grating to be optimized under different parameters in one embodiment. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0051] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0052] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0053] In one embodiment, combined Figure 1 This paper presents a co-design method for micro / nano gratings and photocathodes, treating the micro / nano gratings and photocathodes as a single system. Using their spectral response as the objective function, and combining electromagnetic simulation and optimization algorithms, the design optimization of the micro / nano grating-photocathode system is achieved, avoiding the neglect of the coupling effect between the micro / nano grating and photocathode in traditional methods. The method includes:

[0054] Step 1: Establish a structural model of the micro / nano grating-photocathode system, and clarify the optimization objectives, the objects to be optimized, and the process constraints;

[0055] Step 2: Establish a complex refractive index-wavelength correlation model for the photocathode to obtain the complex refractive index distribution of the photocathode in the target wavelength band;

[0056] Step 3: Determine the set of parameters to be optimized, and set the initial values ​​of each parameter in the set of parameters to be optimized;

[0057] Step 4: Based on the electromagnetic simulation model, calculate the electric field distribution of the micro / nano grating-photocathode system under the current parameter combination;

[0058] Step 5: Calculate the spectral response of the micro / nano grating-photocathode system in the target wavelength band based on the electric field distribution within the photocathode layer;

[0059] Step 6: Establish an objective function with the aim of improving the overall spectral response performance of the system in the target band, and use a parameter optimization algorithm to iteratively search the set of parameters to be optimized until the convergence condition is met, and output the optimal parameter combination.

[0060] Furthermore, in one embodiment, the optimization objective in step 1 is to improve the spectral response of the photocathode in a specific wavelength band, wherein the specific wavelength band is the 380nm-900nm band or a subset thereof; the object to be optimized is a micro-nano grating-photocathode system, which includes at least an incident light window, a micro-nano grating layer and a photocathode layer arranged sequentially along the incident light propagation direction, wherein the micro-nano grating layer is disposed between the incident light window and the photocathode layer.

[0061] Furthermore, in one embodiment, the process constraints in step 1 are photocathode parameters affected by the actual manufacturing process, specifically including one or more combinations of photocathode thickness, photocathode structural parameters, photoelectron emission depth, and photocathode cutoff wavelength.

[0062] Furthermore, in one embodiment, in step 2, the complex refractive index-wavelength correlation model of the photocathode is expressed as:

[0063]

[0064] In the formula, The refractive index of the photocathode is denoted as . Extinction coefficient, The imaginary unit is used to characterize the dynamic changes in the refractive index and extinction coefficient of a photocathode with the wavelength of incident light. Indicates the wavelength of the incident light.

[0065] Furthermore, in one embodiment, the set of parameters to be optimized in step 3 is: any subset of, where The grating constant is The ridge width of the grating, The duty cycle of the grating. The groove depth of the grating. The thickness of the photocathode. λ is the wavelength of the incident light.

[0066] Furthermore, in one embodiment, in step 4, the electric field distribution of the micro / nano grating-photocathode system is obtained by performing multi-wavelength scanning simulation calculations on a system model under a given parameter combination; the electromagnetic simulation model is implemented using any one of the following: rigorous coupled-wave analysis, finite-difference time-domain method, or finite element method; any point within the photocathode layer... The normalized electric field amplitude at point is denoted as .

[0067] Furthermore, in one embodiment, in step 5, the spectral response is determined by the quantum efficiency spectrum. or response spectrum Characterization;

[0068] The quantum efficiency spectrum Satisfy the following formula:

[0069]

[0070] In the formula, For photocathode pair with wavelength of The light absorption coefficient, Indicates wavelength as Light in the photocathode layer The probability that the photoelectrons excited at the point of emission will eventually be emitted from the surface of the photocathode. The volume of the photocathode layer;

[0071] The response spectrum pass The transformation is obtained, and the transformation formula is:

[0072]

[0073] Preferably, in some embodiments, the photocathode has a wavelength of light absorption coefficient Calculate using the following formula:

[0074]

[0075] In the formula, It is Planck's constant. The speed of light in a vacuum. It is the energy corresponding to the cutoff wavelength of the photocathode. It is a constant.

[0076] Preferably, in some embodiments, the wavelength is Light in the photocathode layer The probability that the photoelectrons excited at the point will eventually be emitted from the surface of the photocathode. Calculate using the following formula:

[0077]

[0078] In the formula, P represents the cathode structural parameter, used to reflect the degree of order and photoelectric emission performance of the cathode thin film; when the photocathode is a polycrystalline photocathode with an electron affinity higher than a preset threshold and a long-range disordered and short-range ordered structure, the value is taken as... Otherwise take ; and All of these are constants related to photocathode technology; The thickness of the photocathode; Spatial location point The component in the normal direction of the cathode layer.

[0079] Furthermore, in one embodiment, the objective function in step 6 is the integral of the quantum efficiency spectrum within the target wavelength band, expressed as:

[0080]

[0081] In the formula, , These are the lower and upper limits of the band to be optimized, respectively.

[0082] Furthermore, in one embodiment, the iterative search process of the parameter optimization algorithm in step 6 specifically includes:

[0083] Sampling is performed within the parameter space to be optimized, and a proxy model is established based on the obtained sample parameter set.

[0084] The parameter optimization algorithm is used to select a new set of candidate parameters in the proxy model.

[0085] Repeatedly calculate the spectral response of the micro / nano grating-photocathode system and update the surrogate model until the convergence condition is met and the optimal parameter combination is obtained.

[0086] Preferably, in some embodiments, the parameter optimization algorithm includes at least one of particle swarm optimization, simulated annealing, and genetic algorithm.

[0087] In one embodiment, a co-design system for micro / nano gratings and photocathodes is provided, the system comprising:

[0088] The first module is used to: establish a structural model of the micro / nano grating-photocathode system, and clarify the optimization objectives, the objects to be optimized, and the process constraints;

[0089] The second module is used to: establish a complex refractive index-wavelength correlation model for the photocathode and obtain the complex refractive index distribution of the photocathode in the target wavelength band;

[0090] The third module is used to: determine the set of parameters to be optimized, and set the initial values ​​of each parameter in the set of parameters to be optimized;

[0091] The fourth module is used to calculate the electric field distribution of the micro / nano grating-photocathode system under the current parameter combination based on the electromagnetic simulation model.

[0092] The fifth module is used to calculate the spectral response of the micro / nano grating-photocathode system in the target wavelength band based on the electric field distribution within the photocathode layer.

[0093] The sixth module is used to: establish an objective function with the aim of improving the overall spectral response performance of the system in the target band, use a parameter optimization algorithm to iteratively search the set of parameters to be optimized until the convergence condition is met, and output the optimal parameter combination.

[0094] Specific limitations regarding the co-design system of micro / nano gratings and photocathodes can be found in the above-described limitations of the co-design method for micro / nano gratings and photocathodes, and will not be repeated here. Each module in the aforementioned co-design system of micro / nano gratings and photocathodes can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0095] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements:

[0096] Step 1: Establish a structural model of the micro / nano grating-photocathode system, and clarify the optimization objectives, the objects to be optimized, and the process constraints;

[0097] Step 2: Establish a complex refractive index-wavelength correlation model for the photocathode to obtain the complex refractive index distribution of the photocathode in the target wavelength band;

[0098] Step 3: Determine the set of parameters to be optimized, and set the initial values ​​of each parameter in the set of parameters to be optimized;

[0099] Step 4: Based on the electromagnetic simulation model, calculate the electric field distribution of the micro / nano grating-photocathode system under the current parameter combination;

[0100] Step 5: Calculate the spectral response of the micro / nano grating-photocathode system in the target wavelength band based on the electric field distribution within the photocathode layer;

[0101] Step 6: Establish an objective function with the aim of improving the overall spectral response performance of the system in the target band, and use a parameter optimization algorithm to iteratively search the set of parameters to be optimized until the convergence condition is met, and output the optimal parameter combination.

[0102] For specific limitations on each step, please refer to the above limitations on the co-design method of micro / nano gratings and photocathodes, which will not be repeated here.

[0103] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program being implemented when executed by a processor:

[0104] Step 1: Establish a structural model of the micro / nano grating-photocathode system, and clarify the optimization objectives, the objects to be optimized, and the process constraints;

[0105] Step 2: Establish a complex refractive index-wavelength correlation model for the photocathode to obtain the complex refractive index distribution of the photocathode in the target wavelength band;

[0106] Step 3: Determine the set of parameters to be optimized, and set the initial values ​​of each parameter in the set of parameters to be optimized;

[0107] Step 4: Based on the electromagnetic simulation model, calculate the electric field distribution of the micro / nano grating-photocathode system under the current parameter combination;

[0108] Step 5: Calculate the spectral response of the micro / nano grating-photocathode system in the target wavelength band based on the electric field distribution within the photocathode layer;

[0109] Step 6: Establish an objective function with the aim of improving the overall spectral response performance of the system in the target band, and use a parameter optimization algorithm to iteratively search the set of parameters to be optimized until the convergence condition is met, and output the optimal parameter combination.

[0110] For specific limitations on each step, please refer to the above limitations on the co-design method of micro / nano gratings and photocathodes, which will not be repeated here.

[0111] As a specific example, the invention will be further verified and illustrated in one embodiment.

[0112] First, a structural model of the micro / nano grating-photocathode system is established, such as... Figure 2 As shown, the structure includes at least a transmission window, a micro / nano grating layer, and a photocathode layer. Incident light enters from one side of the transmission window, passes through the micro / nano grating, and then enters the photocathode. The substrate material of the grating to be optimized is SiO2 with a refractive index of 1.46, and the square trenches are filled with a high refractive index (n=2.5) medium.

[0113] The optimization objective is to maximize the response of the micro / nano grating-photocathode system in the 600-900 nm wavelength range. Based on the actual photocathode fabrication conditions, the values ​​of relevant parameters are determined as follows: cathode thickness. The energy corresponding to the cutoff wavelength of the photocathode Cathode structural parameters , ;

[0114] The second step is to establish a complex refractive index-wavelength correlation model for the photocathode, and obtain the n and k distributions of the photocathode at different wavelengths, as shown in the attached figure. Figure 3 As shown;

[0115] The third step is to determine the set of optimization parameters. Set the initial parameter set as ;

[0116] The fourth step involves establishing an electromagnetic simulation model based on the finite element method. Multi-wavelength scanning is then performed on the micro / nano grating-photocathode system under given parameter combinations to calculate the electric field distribution of the system at each incident wavelength. Within the system... The normalized electric field amplitude at point is denoted as ;

[0117] The fifth step is to calculate the spectral response of the photocathode in the target wavelength band based on the electric field distribution of the cathode layer. And calculate its integral in the target band; The calculation formula is:

[0118]

[0119] The sixth step is to write a simulated annealing parameter optimization algorithm program, which automatically samples the parameter space to be optimized, establishes a surrogate model based on the sample parameter set, selects a new candidate parameter set in combination with the optimization algorithm, and repeatedly calculates the spectral response of the micro-nano grating-photocathode system until the conditions are met, and obtains the optimal parameter combination to complete the optimization design.

[0120] Table 1 shows some parameter updates and objective function values ​​during the simulated annealing algorithm parameter optimization process.

[0121] Table 1. Partial parameter updates and objective function values

[0122] 650.00 0.50 575.00 52.32 817.81 0.45 586.39 84.10 848.88 0.49 553.60 58.62 945.42 0.41 590.80 52.56 905.91 0.53 609.68 55.19 758.32 0.44 576.94 57.06 862.21 0.43 614.88 51.70 862.21 0.41 570.72 55.66 785.74 0.42 599.84 56.41 870.67 0.44 602.83 51.87 899.26 0.46 601.03 55.25 833.64 0.46 597.64 84.73 831.88 0.47 615.18 80.42 856.13 0.46 611.33 54.75 849.51 0.47 591.87 58.39 829.71 0.48 596.44 85.73 845.89 0.48 597.00 59.24 830.10 0.47 592.23 86.48 825.70 0.47 601.39 82.76

[0123] The results show that the parameter set is At that time, the micro-nano grating-photocathode system achieves the highest integral quantum efficiency in the target wavelength band.

[0124] The quantum efficiency spectra of the micro / nano grating-photocathode system under different parameter combinations were further compared, and the results are as follows: Figure 4 As shown, where For the initial parameter set, The quantum efficiency spectrum of the system with the optimal parameter set and without a grating, using a single photocathode, is obtained. The results show that the quantum efficiency of the system is significantly improved in the target wavelength band under the optimal parameter set.

[0125] The proposed method for co-designing micro / nano gratings and photocathodes fully considers the electromagnetic and photoelectric coupling between the two and the limitations of actual processes. It has the advantages of high design accuracy, strong targeting, and good feasibility, and can significantly improve the detection sensitivity of weak light detectors.

[0126] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A method for the collaborative design of micro / nano gratings and photocathodes, characterized in that, The method includes: Step 1: Establish a structural model of the micro / nano grating-photocathode system, and clarify the optimization objectives, the objects to be optimized, and the process constraints; Step 2: Establish a complex refractive index-wavelength correlation model for the photocathode to obtain the complex refractive index distribution of the photocathode in the target wavelength band; Step 3: Determine the set of parameters to be optimized, and set the initial values ​​of each parameter in the set of parameters to be optimized; Step 4: Based on the electromagnetic simulation model, calculate the electric field distribution of the micro / nano grating-photocathode system under the current parameter combination; Step 5: Calculate the spectral response of the micro / nano grating-photocathode system in the target wavelength band based on the electric field distribution within the photocathode layer; Step 6: Establish an objective function with the aim of improving the overall spectral response performance of the system in the target band, and use a parameter optimization algorithm to iteratively search the set of parameters to be optimized until the convergence condition is met, and output the optimal parameter combination.

2. The method for co-designing micro / nano gratings and photocathodes according to claim 1, characterized in that, The optimization objective in step 1 is to improve the spectral response of the photocathode in a specific wavelength band, which is the 380nm-900nm wavelength band or a subset thereof; the object to be optimized is a micro-nano grating-photocathode system, which includes at least an incident light window, a micro-nano grating layer and a photocathode layer arranged sequentially along the incident light propagation direction, with the micro-nano grating layer disposed between the incident light window and the photocathode layer.

3. The method for co-designing micro / nano gratings and photocathodes according to claim 1, characterized in that, The process constraints mentioned in step 1 are photocathode parameters affected by the actual manufacturing process, specifically including one or more combinations of photocathode thickness, photocathode structural parameters, photoelectron emission depth, and photocathode cutoff wavelength.

4. The method for co-designing micro / nano gratings and photocathodes according to claim 1, characterized in that, In step 2, the complex refractive index-wavelength correlation model of the photocathode is expressed as: In the formula, The refractive index of the photocathode is denoted as . Extinction coefficient, The imaginary unit is used to characterize the dynamic changes in the refractive index and extinction coefficient of a photocathode with the wavelength of incident light. Indicates the wavelength of the incident light.

5. The method for co-designing micro / nano gratings and photocathodes according to claim 1, characterized in that, The set of parameters to be optimized in step 3 is any subset of, where The grating constant is The ridge width of the grating, The duty cycle of the grating. The groove depth of the grating. The thickness of the photocathode. λ is the wavelength of the incident light.

6. The method for co-designing micro / nano gratings and photocathodes according to claim 1, characterized in that, In step 4, the electric field distribution of the micro / nano grating-photocathode system is obtained through multi-wavelength scanning simulation calculations on a system model with a given combination of parameters; the electromagnetic simulation model is implemented using any one of the following: rigorous coupled-wave analysis, finite-difference time-domain method, or finite element method; any point within the photocathode layer... The normalized electric field amplitude at point is denoted as .

7. The method for co-designing micro / nano gratings and photocathodes according to claim 1, characterized in that, In step 5, the spectral response is determined by the quantum efficiency spectrum. or response spectrum Characterization; The quantum efficiency spectrum Satisfy the following formula: In the formula, For photocathode pair with wavelength of The light absorption coefficient, Indicates wavelength as Light in the photocathode layer The probability that the photoelectrons excited at a certain point will eventually be emitted from the surface of the photocathode, where V is the volume of the photocathode layer; The response spectrum pass The transformation is obtained, and the transformation formula is: 。 8. The method for co-designing micro / nano gratings and photocathodes according to claim 7, characterized in that, The photocathode has a wavelength of light absorption coefficient Calculate using the following formula: In the formula, It is Planck's constant. The speed of light in a vacuum. It is the energy corresponding to the cutoff wavelength of the photocathode. It is a constant; The wavelength is Light in the photocathode layer The probability that the photoelectrons excited at the point will eventually be emitted from the surface of the photocathode. Calculate using the following formula: In the formula, P represents the cathode structural parameter, used to reflect the degree of order and photoelectric emission performance of the cathode thin film; when the photocathode is a polycrystalline photocathode with an electron affinity higher than a preset threshold and a long-range disordered and short-range ordered structure, the value is taken as... Otherwise take ; and All of these are constants related to photocathode technology; The thickness of the photocathode; Spatial location point The component in the normal direction of the cathode layer.

9. The method for co-designing micro / nano gratings and photocathodes according to claim 7, characterized in that, The objective function mentioned in step 6 is the integral of the quantum efficiency spectrum within the target wavelength band, expressed as: In the formula, , These are the lower and upper limits of the band to be optimized, respectively.

10. The method for co-designing micro / nano gratings and photocathodes according to claim 7, characterized in that, The iterative search process of the parameter optimization algorithm described in step 6 specifically includes: Sampling is performed within the parameter space to be optimized, and a proxy model is established based on the obtained sample parameter set. The parameter optimization algorithm is used to select a new set of candidate parameters in the proxy model. Repeatedly calculate the spectral response of the micro / nano grating-photocathode system and update the surrogate model until the convergence condition is met to obtain the optimal parameter combination.

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