Numerical simulation method and system for millisecond laser irradiation fishbone-shaped position sensitive detector

Abstract

The invention discloses a numerical simulation method and system for a millisecond laser irradiation fishbone-shaped position sensitive detector. Based on a heat conduction principle, an elastic-plastic model and a Darcy law, a heat-force coupling model of the millisecond laser irradiation position sensitive detector is established through a finite element method. Through a millisecond laser irradiation experiment, the effectiveness of the millisecond laser irradiation position sensitive detector simulation model is verified. According to the method, the laser energy density and the spot radius are imported into the model, so that the temperature field and stress field distribution of the position sensitive detector can be calculated through the internal mathematical theory, theoretical and simulation basis is provided for long-pulse laser damage to the multilayer structure photoelectric detector, and the application accuracy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser damage, and in particular relates to a numerical simulation method and system for a millisecond laser irradiated fishbone-shaped position sensitive detector. Background Art

[0002] Position-Sensitive Detectors (PSDs), optoelectronic devices with high resolution, short response time, and low manufacturing cost, are widely used in various fields, especially in guidance technology and precision measurement. Lasers can be divided into two categories: continuous and pulsed. Pulsed lasers can be categorized as millisecond, microsecond, and nanosecond lasers. Millisecond lasers offer technical advantages such as precise control of energy distribution in time and space, short process cycles, and high material modification efficiency. The damage mechanism of long-pulsed lasers on photodetectors and their constituent materials has long been a key research topic for experts and scholars.

[0003] In 2013, Li Zewen simulated and experimentally studied the surface damage morphology and dark current changes of photodiodes after laser irradiation, which has important implications for other types of silicon-based positive-intrinsic-negative (PIN) photodetectors irradiated by laser. In 2018, Wang Di simulated and established an electrical model of a silicon-based APD detector subjected to long-pulse lasers. He analyzed the electric field patterns formed by laser-irradiated silicon-based APD (Avalanche Photo Diode) detectors, providing a theoretical basis for laser protection. In 2022, Li Chenang et al. studied a four-quadrant detector irradiated by millisecond lasers through simulation and experiment, analyzing the time-varying characteristics of the output current of each unit quadrant and laying the foundation for studying the mechanism of laser-induced electrical parameter degradation in photodetectors. In 2022, Li Xinlei et al. experimentally measured the recovery time of a silicon-based PIN detector under different bias voltages, pulse widths, and energy densities, determined the recovery time variation pattern, and analyzed the mechanism by which laser influences the recovery time of the device output signal. In 2024, Chinese patent document CN117852361B disclosed a damage time prediction method and system for laser irradiated metal materials.

[0004] Currently, extensive research has been conducted on the damage effects of laser irradiation on PIN photodetectors, charge-coupled detectors, and four-quadrant detectors. Position-sensitive detectors offer numerous advantages, including high efficiency and speed. Current research focuses on improving their detection and positioning accuracy, reducing nonlinear errors, improving substrate material structure, and addressing measurement applications. However, as functional devices, research on functional damage to detectors is relatively limited. Material damage under varying parameters is primarily determined through repeated, extensive experiments and simulations. This approach is not only time-consuming and resource-intensive, but also difficult to perform under certain specific experimental conditions, resulting in numerous limitations. Summary of the Invention

[0005] The present invention aims to provide a numerical simulation method and system for a millisecond laser irradiated fishbone-shaped position sensitive detector, thereby improving accuracy and expanding the scope of application.

[0006] To achieve the purpose of the present invention, on the one hand, the present invention provides a numerical simulation method for a fishbone-shaped position sensitive detector irradiated by millisecond laser, comprising the following steps:

[0007] Step 1: Using the two-dimensional cross-section of the position sensitive detector, simplify the structure of each layer of material into a geometric shape;

[0008] Step 2: Setting the physical parameters of the material, key parameters of the laser used, and a heat source model, and establishing a geometric model through simplified geometric shapes. The physical parameters of the material include the physical parameters of the material of each functional layer of the position sensitive detector;

[0009] Step 3: Based on the heat conduction theory, elastic-plastic model, and Darcy's law, the temperature field control equation and stress field control equation are established through the geometric model using the finite element method;

[0010] Step 4: setting the boundary conditions and initial conditions of the temperature field and the boundary conditions and initial conditions of the stress field to solve the temperature field control equation and the stress field control equation. The boundary conditions of the temperature field are edge adiabatic conditions, the initial conditions of the temperature field are ambient temperature, the boundary conditions of the stress field are fixed constraints and applied boundary loads, and the initial conditions of the stress field are set to no initial displacement and no initial structural velocity field.

[0011] Step 5: Divide the finite element mesh. The finite element is a continuous and limited number of simple units divided by the geometric model. The division method is to use mapped meshes with different distributions to divide the geometrically neat areas and use free triangle meshes to divide the remaining areas.

[0012] Step 6: Based on the finite element grid, obtain the temperature field and stress field distribution of the simulated position sensitive detector through iterative calculation;

[0013] Step 7: Conduct a laser irradiation experiment, and compare the experimental results with the temperature field and stress field distribution of the simulated position sensitive detector to verify the effectiveness of the numerical simulation method;

[0014] Step 8: Combine the temperature field and stress field distribution of the position sensitive detector obtained through simulation and experiment to analyze the damage process and damage threshold of the position sensitive detector irradiated by millisecond laser.

[0015] On the other hand, the present invention also provides a damage threshold analysis system for a numerical simulation method of a fishbone position sensitive detector irradiated by millisecond laser, comprising the following modules:

[0016] Finite element analysis module, used to establish the geometric model of the millisecond laser irradiation position sensitive detector and perform meshing;

[0017] Parameter selection module, used to select different laser energy densities;

[0018] The experimental verification module is used to verify the model through millisecond laser irradiation experiments, and compare the temperature rise curves obtained by experiment and simulation, and compare the experimental damage morphology and the stress curve obtained by simulation;

[0019] A damage threshold calculation module is used to calculate the material damage threshold based on input parameters;

[0020] Laser irradiation experimental platform module, used to build the experimental environment, control irradiation time and parameters, and record the temperature change curve of the center point of the position sensitive detector surface over time and the dynamic damage process;

[0021] Finite element analysis module, used to perform numerical simulation on the finite element analysis model of the millisecond laser irradiated position sensitive detector, and extract the temperature field and stress field distribution of the position sensitive detector and the temperature and stress variation curves of the center point of the position sensitive detector surface over time;

[0022] The curve comparison module is used to compare the temperature rise curve obtained by experiment with the temperature rise curve obtained by simulation, and to compare the experimental damage morphology with the stress curve obtained by simulation to judge the validity of the model.

[0023] Compared with the existing technology, the significant progress of the present invention lies in: (1) High-precision simulation: Through precise finite element analysis, the model of the present invention can simulate in detail the temperature changes of position-sensitive detectors during laser irradiation, providing accurate basic data for damage threshold analysis; (2) Experimental verification: The present invention ensures the accuracy of the model in practical application by comparing actual laser irradiation experiments with simulation results; (3) Wide applicability: The present invention is not only applicable to specific types of position-sensitive detectors, but can also be extended to other types of photoelectric detectors and different laser irradiation conditions.

[0024] In order to more clearly illustrate the functional characteristics and structural parameters of the present invention, further description is given below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 is a flow chart of the steps of the present invention;

[0027] Figure 2 Schematic diagram of the damage mechanism of the position sensitive detector irradiated by millisecond laser of the present invention;

[0028] Figure 3 It is a two-dimensional modeling schematic diagram of the numerical simulation method of the millisecond laser irradiation position sensitive detector of the present invention;

[0029] Figure 4 Schematic diagram of finite element meshing of the present invention, wherein (a) is a schematic diagram of meshing of a geometric model; (b) is an enlarged view of the area marked in (a), showing a specially refined mesh;

[0030] Figure 5 Figure 1 is a comparison of the experimental and simulated temperature rises under different experimental parameters of the present invention, where Figure (a) corresponds to a laser energy density of 144.87 J / cm2, Figure (b) corresponds to a laser energy density of 165.33 J / cm2, Figure (c) corresponds to a laser energy density of 221.55 J / cm2, Figure (d) corresponds to a laser energy density of 280.95 J / cm2, and Figure (e) corresponds to a laser energy density of 302.97 J / cm2;

[0031] Figure 6 : are instantaneous temperature field distribution diagrams of a position-sensitive detector irradiated by millisecond laser under different experimental parameters of the present invention, wherein (a) is a diagram showing the temperature changing with the position on the X-axis, and (b) is a diagram showing the temperature changing with the position on the Y-axis;

[0032] Figure 7 is a graph showing changes in pyrolysis gas pressure over time under different experimental parameters of the present invention;

[0033] Figure 8 1 is a graph showing the instantaneous stress field distribution of the plastic packaging material under different experimental parameters of the present invention, wherein (a) is a graph showing the stress variation with position on the X-axis, and (b) is a graph showing the stress variation with position on the Y-axis;

[0034] Figure 9 is a simulated stress curve diagram of the fracture moment of the present invention;

[0035] Figure 10 These are damage morphology images recorded by the high-speed camera of the present invention under different experimental parameters. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] The numerical simulation method of the present invention for a millisecond laser irradiated fishbone position sensitive detector is combined with Figure 1 , including the following steps:

[0038] Step 1. Using the two-dimensional cross-section (length × height) of the position-sensitive detector, simplify the structure of each layer of material into a reasonable geometric shape; the structure of each layer of material includes a plastic package, an aluminum plate, a silicon base, and an air layer gap. The external plastic package, the air layer gap, and the internal bottom aluminum plate are set as a rectangle. The internal upper silicon base is based on the rectangle and a periodically distributed photosensitive surface is set: the photosensitive area and the isolation area are periodically alternately distributed.

[0039] Step 2: Setting the physical parameters of the material, key parameters of the laser used, and a heat source model, and establishing a geometric model through simplified geometric shapes. The physical parameters of the material include the physical parameters of the material of each functional layer of the position sensitive detector;

[0040] The physical parameters of the material to be set include the structural dimensions and material parameters of the position sensitive detector, the structural dimensions include length, width and thickness, the material parameters include density, specific heat capacity and thermal conductivity, the key parameters of the laser used include laser power density and spot radius, and the heat source model is a Gaussian distributed surface heat source model, and the expression is:

[0041] ;

[0042] ;

[0043] ;

[0044] in, is the heat source, I0 is the peak power density of the incident laser at the center of the spot; R(T) and α(T, y) represent the reflectivity and absorption coefficient of silicon respectively; f(x) is the spatial distribution of the laser pulse, g(t) is the temporal distribution of the laser pulse; a is the beam radius, is the time, τ is the laser pulse width; T is the temperature, and x and y are the position coordinates.

[0045] Step 3: Based on the heat conduction theory, elastic-plastic model, and Darcy's law, the temperature field control equation and stress field control equation are established through the geometric model using the finite element method;

[0046] The temperature field control equation is:

[0047] ;

[0048] Where [C] is the heat capacity matrix, {T} is the temperature vector, [K th ] is the heat conduction matrix, {Q} is the heat source vector, represents the differential of the temperature vector {T} with respect to time t;

[0049] The stress field governing equation is:

[0050] ;

[0051] ;

[0052] ;

[0053] Where {∆σ} is stress, [D] ep is the elastoplastic matrix, {∆ε} is the total strain, {∆ε th} is the elastic strain, [D] e is the elastic matrix, T is the temperature, {σ} is the stress matrix, is the mean stress, is the hardening modulus, Represents the differential of temperature T with respect to time t.

[0054] Step 4: setting the boundary conditions and initial conditions of the temperature field and the boundary conditions and initial conditions of the stress field to solve the temperature field control equation and the stress field control equation. The boundary conditions of the temperature field are edge adiabatic conditions, the initial conditions of the temperature field are ambient temperature, the boundary conditions of the stress field are fixed constraints and applied boundary loads, and the initial conditions of the stress field are set to no initial displacement and no initial structural velocity field.

[0055] The edge adiabatic boundary condition of the temperature field in step 4 is:

[0056] ;

[0057] The initial conditions of the temperature field in step 4 are:

[0058]

[0059] Where L is the length of the photosensitive surface, H is the total thickness of the aluminum plate and the silicon substrate, T0 is the initial temperature 300K, k is the thermal conductivity, t is the time, T is the temperature, x and y are the position coordinates, is the temperature at time t at x, y;

[0060] The fixed constraint boundary conditions of the stress field are:

[0061] ;

[0062] The applied boundary load of the stress field is the pyrolysis gas pressure:

[0063] ;

[0064] Where, К is the permeability of porous media, ρ g is the pyrolysis gas density, R is the universal gas constant, M g is the molar mass of pyrolysis gas, u is the displacement, is the average displacement of pyrolysis gas, is the pyrolysis gas displacement, is the volume fraction of pyrolysis gas, is the pyrolysis gas pressure;

[0065] The initial conditions of the stress field are:

[0066] ;

[0067] in, is the displacement in the x direction, is the displacement in the y direction, is the structural velocity in the x direction, is the structural velocity in the y direction.

[0068] Step 5: Divide the finite element mesh. The finite element is a continuous and limited number of simple units divided by the geometric model. The division method is to use mapped meshes with different distributions to divide the geometrically neat areas and use free triangle meshes to divide the remaining areas.

[0069] The division method is as follows: silicon material is the main part that absorbs light energy and is the main area for heat deposition. Large temperature gradients and stress gradients exist nearby, and a special refined grid division is performed on the silicon material area.

[0070] Step 6: Based on the finite element grid, obtain the temperature field and stress field distribution of the simulated position sensitive detector through iterative calculation;

[0071] Step 7: Conduct a laser irradiation experiment, and compare the experimental results with the temperature field and stress field distribution of the simulated position sensitive detector to verify the effectiveness of the numerical simulation method;

[0072] 7-1. Verify the numerical simulation method through millisecond laser irradiation experiments, control the laser irradiation time, and select different laser energy densities as experimental parameters;

[0073] 7-2. Build a millisecond laser irradiation experimental platform and use an infrared point pyrometer to measure temperature. The temperature curve of the center point on the surface of the position-sensitive detector as a function of time t is obtained using the data measured by the infrared point pyrometer and the surface emissivity compensation model.

[0074] 7-3. Compare the temperature rise curve obtained from the experiment with the temperature rise curve obtained from the simulation to verify the effectiveness of the temperature simulation module;

[0075] 7-4. Record the damage process with a high-speed camera and take screenshots according to the frame number to obtain the damage morphology at different times;

[0076] 7-5. Compare the damage morphology recorded by the high-speed camera with the stress simulation results to verify the effectiveness of the stress simulation module;

[0077] 7-6. If the deviation between the experimental results and the simulation results is small, it is considered that the numerical simulation method can better simulate the millisecond laser irradiation process.

[0078] Step 8: Combine the temperature field and stress field distribution of the position sensitive detector obtained through simulation and experiment to analyze the damage process and damage threshold of the position sensitive detector irradiated by millisecond laser.

[0079] In addition, the present invention provides a damage threshold analysis system for a numerical simulation method of a fishbone position sensitive detector irradiated by millisecond laser, including the following modules:

[0080] Finite element analysis module, used to establish the geometric model of the millisecond laser irradiation position sensitive detector and perform meshing;

[0081] Parameter selection module, used to select different laser energy densities;

[0082] The experimental verification module is used to verify the model through millisecond laser irradiation experiments, and compare the temperature rise curves obtained by experiment and simulation, and compare the experimental damage morphology and the stress curve obtained by simulation;

[0083] A damage threshold calculation module is used to calculate the material damage threshold based on input parameters;

[0084] Laser irradiation experimental platform module, used to build the experimental environment, control irradiation time and parameters, and record the temperature change curve of the center point of the position sensitive detector surface over time and the dynamic damage process;

[0085] Finite element analysis module, used to perform numerical simulation on the finite element analysis model of the millisecond laser irradiated position sensitive detector, and extract the temperature field and stress field distribution of the position sensitive detector and the temperature and stress variation curves of the center point of the position sensitive detector surface over time;

[0086] The curve comparison module is used to compare the temperature rise curve obtained by experiment with the temperature rise curve obtained by simulation, and to compare the experimental damage morphology with the stress curve obtained by simulation to judge the validity of the model.

[0087] Example

[0088] Based on Figure 2 The physical process shown in FIG. 1 is a schematic diagram of a two-dimensional numerical simulation model of the present invention. Figure 3 As shown. On the basis of ensuring the reliability of the numerical calculation results, the following assumptions and simplifications are made to the model:

[0089] (1) Assume that the materials of each functional layer of the device have uniform and isotropic characteristics;

[0090] (2) Considering that the geometric size of the model is much larger than the laser spot diameter, the boundary is set to an adiabatic condition, that is, heat will not be transferred to the boundary area during laser irradiation;

[0091] (3) The bottom surface of the model also adopts adiabatic boundary conditions;

[0092] (4) Neglecting the convective heat transfer and thermal radiation effects at the boundaries in thermodynamic analysis;

[0093] (5) Liquid phase convection is not considered. If there is a liquid phase area, it is treated as heat conduction.

[0094] The detailed working principle of this method is:

[0095] Step 1: Geometry Modeling

[0096] like Figure 3 As shown, the upper inner layer is a doped silicon wafer. The p-type and n-type regions of the device are heavily doped through diffusion or ion implantation. The lower inner layer is an aluminum plate, which serves as an electrode, both diffusing heat and reflecting some light energy. The outer layer is a plastic package made of polymethyl methacrylate (PMMA), which transmits laser light without attenuating the energy. Specifically, to calculate the pressure of the pyrolysis gas from the plastic package, an air gap is placed at the interface between the silicon wafer and the plastic package.

[0097] Step 2: Physical Modeling

[0098] like Figure 2 As shown, the position-sensitive detector studied in this paper primarily consists of three layers of material: silicon, plastic encapsulation, and aluminum electrodes. When a millisecond laser irradiates the surface of a silicon-based position-sensitive detector, the plastic encapsulation absorbs almost no light. Considering the non-negligible skin depth of the silicon material when the millisecond laser irradiates the silicon material, the material is considered to be a laser heat source, i.e., volume deposition, or absorption. The heat deposition on the silicon material is calculated based on the spatial and temporal distribution of the laser light, thereby establishing a thermal damage model. Although the plastic encapsulation does not absorb light energy, due to heat conduction during the laser exposure, the plastic encapsulation material, as a thermoplastic resin, undergoes pyrolysis at approximately 200°C. This pyrolysis produces a large amount of pyrolysis gas and black coke. Before the plastic encapsulation is destroyed, the gas pressure in the internal voids exerts pressure upward on the plastic encapsulation and downward on the silicon material. The temperature gradient generated by heat conduction in the material itself can lead to thermal stress damage. Incorporating the effects of gas pressure, a stress damage model for the position-sensitive detector is established.

[0099] Step 3: Parameter setting

[0100] Table 1 Laser parameters of the interaction between millisecond laser and fishbone-shaped one-dimensional position sensitive detector

[0101]

[0102] Table 2 Material parameters of fishbone-shaped one-dimensional position sensitive detector

[0103]

[0104] Table 3 Structure of each layer of fishbone-shaped one-dimensional position sensitive detector

[0105]

[0106] Table 4 Yield strength of silicon materials at different temperatures

[0107]

[0108] Step 4. Boundary conditions and initial conditions

[0109] (1) Boundary conditions and initial conditions of temperature field

[0110] Without considering thermal convection and thermal radiation, the boundary conditions can be written as:

[0111]

[0112] The initial conditions are:

[0113]

[0114] Where L is the length of the photosensitive surface, H is the total thickness of the aluminum plate and the silicon substrate, T0 is 300K, k is the thermal conductivity, t is the time, and x and y are the position coordinates.

[0115] (2) Boundary conditions and initial conditions of stress field

[0116] The boundary conditions of the fixed constraints can be written as:

[0117]

[0118] The boundary conditions for gas pressure are:

[0119]

[0120] Where, К is the permeability of porous media, ρ g is the pyrolysis gas density, R is the universal gas constant, M g is the molar mass of pyrolysis gas, T is the material temperature, u is the displacement, represents the average displacement of pyrolysis gas, represents the pyrolysis gas displacement, represents the volume fraction of pyrolysis gas, Indicates the pyrolysis gas pressure.

[0121] Parameters of plastic package pyrolysis gas:

[0122]

[0123] Therefore, within the range of y = 0 and x ∈ [-L / 2, L / 2], we have

[0124]

[0125] The initial conditions of the stress field are:

[0126] ;

[0127] in, is the displacement in the x direction, is the displacement in the y direction, is the structural velocity in the x direction, is the structural velocity in the y direction.

[0128] Step 5: Mesh generation

[0129] Use mapped meshes with different distributions to divide the geometrically neat areas, and use free triangulated meshes to divide the remaining areas

[0130] Step 6: Finite element calculation

[0131] The instantaneous temperature field and stress field distribution of the position sensitive detector are obtained through finite element iterative calculation;

[0132] Step 7: Conduct a laser irradiation experiment and compare the experimental results with the simulated temperature field and stress field distribution of the position sensitive detector to verify the effectiveness of the numerical simulation method:

[0133] 1. Verify the numerical simulation method through millisecond laser irradiation experiments, control the laser irradiation time, and select different laser energy densities as experimental parameters;

[0134] 2. Build a millisecond laser irradiation experimental platform and use an infrared point pyrometer to measure temperature. The temperature curve of the center point on the surface of the position-sensitive detector as a function of time t is obtained using the data measured by the infrared point pyrometer and the surface emissivity compensation model.

[0135] 3. Compare the temperature rise curve obtained from the experiment with the temperature rise curve obtained from the simulation to verify the effectiveness of the temperature simulation module;

[0136] 4. Record the damage process with a high-speed camera and take screenshots based on the frame number to obtain the damage morphology at different times;

[0137] 5. Compare the damage morphology recorded by the high-speed camera with the stress simulation results to verify the effectiveness of the stress simulation module;

[0138] 6. If the deviation between the experimental results and the simulation results is small, it is considered that the numerical simulation method can better simulate the millisecond laser irradiation process.

[0139] Step 8: Damage Analysis

[0140] Based on the above, the damage process and damage threshold of position sensitive detectors irradiated by millisecond laser are analyzed.

[0141] The carbonization energy density threshold and melting energy density threshold of the position sensitive detector are obtained by comprehensive analysis of temperature field simulation and experimental results. The energy density threshold for plastic package fracture damage is obtained by stress field simulation results and morphological damage analysis.

[0142] This embodiment integrates multiple steps such as finite element analysis, experimental verification, parameter selection, and multi-physics field coupling to efficiently and accurately analyze the damage threshold, providing a theoretical basis for optimizing the design of position-sensitive detectors. This is of great significance for improving the working performance of position-sensitive detectors in high-energy laser environments.

[0143] During the model simulation calculation stage, the main operation process is: select a suitable solver for solving, determine the appropriate simulation step size for the solution time, and here the solution time is selected as 20ms and the simulation step size is 2ms. After completing the above settings, simulation calculation can be carried out.

[0144] In the model post-processing stage, the main operation process is to obtain the temperature rise curve of the center point of the position-sensitive detector surface, the pyrolysis gas pressure change curve with time, the stress change curve of the center point of the position-sensitive detector surface with time, and the temperature and stress change curve of the material at the end of the laser action, thereby obtaining the laser energy density threshold corresponding to the material damage, and outputting it as the material damage threshold.

[0145] The embodiments of the present invention can be implemented by finite element simulation software.

[0146] This embodiment establishes a one-dimensional position sensitive detector with a fishbone-shaped photosensitive surface irradiated by millisecond laser. The grid division and geometric model are as follows: Figure 3 、 Figure 4 As shown in the figure; the laser energy density is selected as the loss input parameter, and the instantaneous temperature field of the material under different energy densities is obtained as shown in the figure. Figure 6 As shown in the figure, the curve of pyrolysis gas pressure changing with time is obtained as shown in the figure Figure 7 As shown, the instantaneous stress field distribution of the plastic packaging material is obtained as Figure 8 As shown in the figure, the effectiveness of the model was verified by laser irradiation experiments, and the temperature simulation results were compared with the experimental results. Figure 5 As shown in the figure, the stress simulation results are compared with the experimental results. Figure 9 、 Figure 10 shown.

[0147] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0148] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A numerical simulation method for a millisecond laser irradiated fishbone position sensitive detector, characterized in that: The following steps are involved: Step 1: Using the two-dimensional cross-section of the position sensitive detector, simplify the structure of each layer of material into a geometric shape; Step 2: Setting the physical parameters of the material, key parameters of the laser used, and a heat source model, and establishing a geometric model through simplified geometric shapes. The physical parameters of the material include the physical parameters of the material of each functional layer of the position sensitive detector; Step 3: Based on the heat conduction theory, elastic-plastic model, and Darcy's law, the temperature field control equation and stress field control equation are established through the geometric model using the finite element method; Step 4: setting the boundary conditions and initial conditions of the temperature field and the boundary conditions and initial conditions of the stress field to solve the temperature field control equation and the stress field control equation. The boundary conditions of the temperature field are edge adiabatic conditions, the initial conditions of the temperature field are ambient temperature, the boundary conditions of the stress field are fixed constraints and applied boundary loads, and the initial conditions of the stress field are set to no initial displacement and no initial structural velocity field. Step 5: Divide the finite element mesh. The finite element is a continuous and limited number of simple units divided by the geometric model. The division method is to use mapped meshes with different distributions to divide the geometrically neat areas and use free triangle meshes to divide the remaining areas. Step 6: Based on the finite element grid, obtain the temperature field and stress field distribution of the simulated position sensitive detector through iterative calculation; Step 7: Conduct a laser irradiation experiment, and compare the experimental results with the temperature field and stress field distribution of the simulated position sensitive detector to verify the effectiveness of the numerical simulation method; Step 8: Combine the temperature field and stress field distribution of the position sensitive detector obtained through simulation and experiment to analyze the damage process and damage threshold of the position sensitive detector irradiated by millisecond laser.

2. The numerical simulation method of a millisecond laser irradiated fishbone position sensitive detector according to claim 1, characterized in that: The structure of each layer of material in step 1 includes plastic packaging, aluminum plate, silicon base and air layer gap. The external plastic packaging, air layer gap and the internal bottom aluminum plate are set to a rectangle. The internal upper silicon base is based on the rectangle and a periodically distributed photosensitive surface is set: the photosensitive area and the isolation area are periodically alternately distributed.

3. The numerical simulation method of a millisecond laser irradiated fishbone position sensitive detector according to claim 1, characterized in that: In step 2, the physical parameters of the material are set, including the structural dimensions and material parameters of the position sensitive detector. The structural dimensions include length, width and thickness. The material parameters include density, specific heat capacity and thermal conductivity. The key parameters of the laser used include laser power density and spot radius. The heat source model is a Gaussian distributed surface heat source model, and the expression is: ； ； ； in, is the heat source, I0 is the peak power density of the incident laser at the center of the spot; R(T) and α(T, y) are the reflectivity and absorption coefficient of silicon respectively; f(x) is the spatial distribution of the laser pulse, g(t) is the temporal distribution of the laser pulse; a is the beam radius, is the time, τ is the laser pulse width; T is the temperature, and x and y are the position coordinates.

4. The numerical simulation method of a millisecond laser irradiated fishbone position sensitive detector according to claim 1, characterized in that: The temperature field control equation in step 3 is: ； Where [C] is the heat capacity matrix, {T} is the temperature vector, [K th ] is the heat conduction matrix, {Q} is the heat source vector, represents the differential of the temperature vector {T} with respect to time t; The stress field control equation in step 3 is: ； ； ； Where {∆σ} is stress, [D] ep is the elastoplastic matrix, {∆ε} is the total strain, {∆ε th } is the elastic strain, [D] e is the elastic matrix, T is the temperature, {σ} is the stress matrix, is the mean stress, is the hardening modulus, Represents the differential of temperature T with respect to time t.

5. The numerical simulation method of a millisecond laser irradiated fishbone position sensitive detector according to claim 1, characterized in that: The edge adiabatic boundary condition of the temperature field in step 4 is: ； The initial conditions of the temperature field in step 4 are:

6. Among them, L is the length of the photosensitive surface, H is the total thickness of the aluminum plate and the silicon substrate, T0 is the initial temperature, k is the thermal conductivity, t is the time, T is the temperature, x and y are the position coordinates, is the temperature at time t at x, y; The fixed constraint boundary conditions of the stress field in step 4 are: ； The applied boundary load of the stress field in step 4 is the pyrolysis gas pressure: ； Where, К is the permeability of porous media, ρ g is the pyrolysis gas density, R is the universal gas constant, M g is the molar mass of pyrolysis gas, u is the displacement, is the average displacement of pyrolysis gas, is the pyrolysis gas displacement, is the volume fraction of pyrolysis gas, is the pyrolysis gas pressure; The initial conditions of the stress field in step 4 are: ； in, is the displacement in the x direction, is the displacement in the y direction, is the structural velocity in the x direction, is the structural velocity in the y direction.

7. The numerical simulation method of a millisecond laser irradiated fishbone position sensitive detector according to claim 1, characterized in that: The division method in step 5 is as follows: the silicon material is the main part that absorbs light energy and is the main area for heat deposition. There are large temperature gradients and stress gradients nearby, so a special and refined grid division is performed on the silicon material area.

8. The numerical simulation method of a millisecond laser irradiated fishbone position sensitive detector according to claim 1, characterized in that: The step 7 specifically includes the following steps: 7-1. Verify the numerical simulation method through millisecond laser irradiation experiments, control the laser irradiation time, and select different laser energy densities as experimental parameters; 7-2. Build a millisecond laser irradiation experimental platform and use an infrared point pyrometer to measure temperature. The temperature curve of the center point on the surface of the position-sensitive detector as a function of time t is obtained using the data measured by the infrared point pyrometer and the surface emissivity compensation model. 7-3. Compare the temperature rise curve obtained from the experiment with the temperature rise curve obtained from the simulation to verify the effectiveness of the temperature simulation module; 7-4. Record the damage process with a high-speed camera and take screenshots according to the frame number to obtain the damage morphology at different times; 7-5. Compare the damage morphology recorded by the high-speed camera with the stress simulation results to verify the effectiveness of the stress simulation module; 7-6. If the deviation between the experimental results and the simulation results is small, it is considered that the numerical simulation method can better simulate the millisecond laser irradiation process.

9. A damage threshold analysis system applied to a numerical simulation method of a fishbone position sensitive detector irradiated by millisecond laser according to any one of claims 1 to 7, characterized in that: Includes the following modules: Finite element analysis module, used to establish the geometric model of the millisecond laser irradiation position sensitive detector and perform meshing; Parameter selection module, used to select different laser energy densities; The experimental verification module is used to verify the model through millisecond laser irradiation experiments, and compare the temperature rise curves obtained by experiment and simulation, and compare the experimental damage morphology and the stress curve obtained by simulation; A damage threshold calculation module is used to calculate the material damage threshold based on input parameters; Laser irradiation experimental platform module, used to build the experimental environment, control irradiation time and parameters, and record the temperature change curve of the center point of the position sensitive detector surface over time and the dynamic damage process; Finite element analysis module, used to perform numerical simulation on the finite element analysis model of the millisecond laser irradiated position sensitive detector, and extract the temperature field and stress field distribution of the position sensitive detector and the temperature and stress variation curves of the center point of the position sensitive detector surface over time; The curve comparison module is used to compare the temperature rise curve obtained by experiment with the temperature rise curve obtained by simulation, and to compare the experimental damage morphology with the stress curve obtained by simulation to judge the validity of the model.

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