Complex medium structure optical mode decomposition method under special point light source and related device

Abstract

The invention discloses an optical mode decomposition method for a complex medium structure under a special point light source and a related device, and relates to the technical field of nano photonics and optical engineering.The method comprises the steps that a finite difference time domain method is adopted, and a three-dimensional geometric model of the complex medium structure is established; based on the three-dimensional geometric model, performing numerical simulation by adopting a finite difference time domain method, and determining electromagnetic field distribution information of the complex medium structure under the irradiation of a special point light source; performing multi-stage decomposition on the electromagnetic field distribution information to obtain a plurality of multi-pole sub-modes; respectively determining two-dimensional far-field radiation information of each multi-pole sub-mode based on the plurality of multi-pole sub-modes; and combining the two-dimensional far-field radiation information of each multi-pole sub-mode to obtain a comprehensive three-dimensional far-field radiation pattern. The optical characteristics of the complex medium structure under the irradiation of the special point light source can be effectively analyzed, and the multipole mode contribution and interaction of the complex medium structure under the irradiation of the special point light source can be accurately reflected.

Description

Technical Field

[0001] The present application relates to the technical fields of nanophotonics and optical engineering, and particularly to an optical mode decomposition method and related device for a complex dielectric structure under a special point light source. Background Art

[0002] Nanophotonics is a scientific field that studies the interaction between light and matter at the nanoscale, aiming to explore and utilize the propagation and scattering characteristics of light in nanostructures (such as metal nanoparticles, photonic crystals, nanofibers, etc.). With the development of basic theories such as quantum mechanics and electromagnetics, as well as the progress of nanofabrication technology, scientists are able to precisely fabricate various nanoscale optical structures and devices, and reveal the basic laws of processes such as light propagation, scattering, absorption, and emission at the nanoscale through theoretical calculations and model establishment. As an independent research field, nanophotonics provides many advanced application prospects for fields such as sensing, imaging, quantum technology, and signal processing. High refractive index dielectric nanostructures exhibit unique capabilities, which stem from the electromagnetic dipole and derived resonance modes of Mie resonance. These modes not only provide additional degrees of freedom for controlling and manipulating the light field, but also enable very narrow resonance bandwidths, which are suitable for applications that require precise spectral selectivity. The magnetic response principle of high refractive index dielectric nanostructures is similar to that of traditional metal split-ring resonators. Its magnetic Mie resonance results from the excitation of specific electromagnetic modes inside the particles, and this mode has important application potential in the visible and infrared spectral regions. In recent years, the research on high refractive index dielectric nanostructures has become a new direction in nanooptics and nanophotonics inspired by metamaterials.

[0003] However, existing optical mode decomposition methods usually rely on the plane wave excitation model, and it is difficult to accurately describe the multipole mode contributions and interactions of complex dielectric structures (such as silicon nanodisks) under the irradiation of special point light sources such as dipole sources, and it is impossible to effectively analyze the optical properties of complex dielectric structures under the irradiation of dipole sources. Especially in practical application scenarios, the use of dipole sources as point light sources is more common because dipole sources can more realistically simulate the light source conditions in practical applications. Therefore, how to provide an optical mode decomposition method for a complex dielectric structure under a special point light source to effectively analyze the optical properties of a complex dielectric structure under the irradiation of a special point light source and accurately reflect the multipole mode contributions and interactions of a complex dielectric structure under the irradiation of a special point light source has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present application is to provide an optical mode decomposition method and related device for a complex dielectric structure under a special point light source, which can effectively analyze the optical properties of a complex dielectric structure under the irradiation of a special point light source and accurately reflect the multipole mode contributions and interactions of a complex dielectric structure under the irradiation of a special point light source.

[0005] To achieve the above object, the present application provides the following solutions:

[0006] In a first aspect, the present application provides a method for decomposing optical modes of a complex dielectric structure under a special point light source. The method for decomposing optical modes of a complex dielectric structure under a special point light source includes the following steps:

[0007] Use the finite-difference time-domain method to establish a three-dimensional geometric model of the complex dielectric structure.

[0008] Based on the three-dimensional geometric model, use the finite-difference time-domain method for numerical simulation to determine the electromagnetic field distribution information of the complex dielectric structure under the irradiation of the special point light source; the electromagnetic field distribution information includes the electric field information, refractive index information, coordinate information of different wavelengths of the special point light source, and the scattering spectrum in each direction.

[0009] Perform multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes.

[0010] Based on multiple multipole modes, respectively determine the two-dimensional far-field radiation information of each multipole mode.

[0011] Merge the two-dimensional far-field radiation information of each multipole mode to obtain a comprehensive three-dimensional far-field radiation map; the comprehensive three-dimensional far-field radiation map is used to characterize the optical properties of the complex dielectric structure under the irradiation of the special point light source and reflect the contributions and interactions of each multipole mode of the complex dielectric structure.

[0012] Optionally, the complex dielectric structure includes a silicon nanodisk with an asymmetric notch, and the special point light source is a dipole source.

[0013] Optionally, based on the three-dimensional geometric model, use the finite-difference time-domain method for numerical simulation to determine the electromagnetic field distribution information of the complex dielectric structure under the irradiation of the special point light source, which specifically includes the following steps:

[0014] Based on the three-dimensional geometric model, use the finite-difference time-domain method for numerical simulation. During the numerical simulation process, use a 3D monitor to obtain the electric field information, refractive index information, and coordinate information of different wavelengths of the special point light source, and use a 2D monitor to obtain the scattering spectrum in each direction of the special point light source.

[0015] Optionally, the multipole modes include ED mode, MD mode, EQ mode, MQ mode, EO mode, and MO mode.

[0016] Performing multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes specifically includes the following steps:

[0017] Import the electromagnetic field distribution information into calculation software, and use the calculation software to perform multi-level decomposition on the electromagnetic field distribution information to obtain the ED mode, MD mode, EQ mode, MQ mode, EO mode, and MO mode.

[0018] Optionally, based on multiple said multipole modes, respectively determine the two-dimensional far-field radiation information of each said multipole mode, specifically including the following steps:

[0019] Convert the Cartesian coordinate system to the spherical coordinate system.

[0020] Based on the spherical coordinate system, calculate the two-dimensional far-field radiation patterns of each said multipole mode respectively.

[0021] Determine the two-dimensional far-field radiation information of each said multipole mode according to the two-dimensional far-field radiation patterns of each said multipole mode.

[0022] Optionally, merge the two-dimensional far-field radiation information of each said multipole mode to obtain a comprehensive three-dimensional far-field radiation pattern, specifically including the following steps:

[0023] Merge the two-dimensional far-field radiation information of each said multipole mode in the order of the phi-axis or theta-axis of the spherical coordinate system to obtain the two-dimensional far-field radiation information in the x-y plane of the entire three-dimensional space.

[0024] According to the two-dimensional far-field radiation information in the x-y plane of the entire three-dimensional space, use drawing software to draw the three-dimensional far-field radiation patterns of each said multipole mode.

[0025] According to the three-dimensional far-field radiation patterns of each said multipole mode, use drawing software to draw a comprehensive three-dimensional far-field radiation pattern.

[0026] Optionally, after the step of merging the two-dimensional far-field radiation information of each said multipole mode to obtain a comprehensive three-dimensional far-field radiation pattern, the optical mode decomposition method of a complex dielectric structure under a special point light source further includes the following steps:

[0027] Use a far-field calculation tool to obtain the three-dimensional far-field electric field information of the target wavelength.

[0028] Generate a three-dimensional far-field radiation pattern based on the far-field calculation tool according to the three-dimensional far-field electric field information of the target wavelength.

[0029] Compare the three-dimensional far-field radiation pattern based on the far-field calculation tool with the comprehensive three-dimensional far-field radiation pattern to verify the accuracy and reliability of the comprehensive three-dimensional far-field radiation pattern.

[0030] In a second aspect, the present application provides a computer device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor executes the computer program to implement the steps of the method for decomposing the optical mode of a complex dielectric structure under a special point light source.

[0031] In a third aspect, the present application provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of the method for decomposing the optical mode of a complex dielectric structure under a special point light source.

[0032] In a fourth aspect, the present application provides a computer program product, including a computer program, and when the computer program is executed by a processor, it implements the steps of the method for decomposing the optical mode of a complex dielectric structure under a special point light source.

[0033] According to the specific embodiments provided by the present application, the present application has the following technical effects:

[0034] The present application provides a method and related device for decomposing the optical mode of a complex dielectric structure under a special point light source. By establishing a three-dimensional geometric model of the complex dielectric structure and combining the numerical simulation process of the finite-difference time-domain method, it can more realistically reflect the interaction between the complex dielectric structure and the special point light source, and more accurately determine the electromagnetic field distribution information of the complex dielectric structure under the irradiation of the special point light source. By performing multi-level decomposition to obtain multiple multipole modes, and then merging according to the two-dimensional far-field radiation information of each multipole mode, a more accurate and reliable comprehensive three-dimensional far-field radiation map can be obtained. Thus, the comprehensive three-dimensional far-field radiation map can be used to effectively analyze the optical characteristics of the complex dielectric structure under the irradiation of the special point light source, accurately reflect the contributions and interactions of each multipole mode of the complex dielectric structure, and can solve the problems that the existing optical mode decomposition methods are difficult to accurately describe the contributions and interactions of the multipole modes of the complex dielectric structure under the irradiation of the special point light source and cannot effectively analyze the optical characteristics of the complex dielectric structure under the irradiation of the dipole source. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 It is an application environment diagram of a method for decomposing the optical mode of a complex dielectric structure under a special point light source provided by an embodiment of the present application.

[0037] Figure 2Flowchart of an optical mode decomposition method for complex dielectric structures under a special point light source provided by an embodiment of the present application.

[0038] Figure 3 Schematic diagram of the three-dimensional geometric model of a notched silicon nanodisk provided by an embodiment of the present application.

[0039] Figure 4 Scattering spectrum diagram of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) provided by an embodiment of the present application.

[0040] Figure 5 Mode decomposition diagram of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) provided by an embodiment of the present application.

[0041] Figure 6 Three-dimensional far-field distribution diagram of a single mode of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 620 nm provided by an embodiment of the present application.

[0042] Figure 7 Three-dimensional far-field distribution diagram of a single mode of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 655 nm provided by an embodiment of the present application.

[0043] Figure 8 Comprehensive three-dimensional far-field distribution diagram of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 620 nm provided by an embodiment of the present application.

[0044] Figure 9 Comprehensive three-dimensional far-field distribution diagram of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 655 nm provided by an embodiment of the present application.

[0045] Figure 10 Three-dimensional far-field radiation diagram based on a far-field calculation tool of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 620 nm provided by an embodiment of the present application.

[0046] Figure 11 Three-dimensional far-field radiation diagram based on a far-field calculation tool of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 655 nm provided by an embodiment of the present application.

[0047] Figure 12 Schematic diagram of the structure of a computer device provided by an embodiment of the present application. Detailed implementation manners

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0049] In nanophotonics, studying the interaction between nanostructures of high refractive index media and incident light is crucial for achieving specific optical responses or enhancement effects. However, in the prior art, when dealing with complex dielectric structures (such as silicon nanodisks with asymmetric designs), it usually relies on the plane wave excitation model, which limits the understanding and optimization of actual application scenarios. Especially in the case of using special point light sources (such as dipole sources), the existing optical mode decomposition methods often cannot accurately describe the contributions and interactions of multipole modes, and cannot effectively analyze the optical properties of complex dielectric structures under the illumination of dipole sources. This embodiment aims to provide an optical mode decomposition method for complex dielectric structures (such as notched silicon nanodisks) under special point light sources (such as dipole sources) to accurately analyze the radiation directions and intensity distributions of each multipole mode at different wavelengths, effectively analyze the optical properties of complex dielectric structures under the illumination of special point light sources, and accurately reflect the contributions and interactions of each multipole mode of complex dielectric structures.

[0050] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] The optical mode decomposition method for complex dielectric structures under special point light sources provided by the embodiments of the present application can be applied to, for example Figure 1In the application environment shown. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be set separately, integrated on the server 104, placed on the cloud or other servers. The terminal 102 can send the basic data for decomposing the optical mode to be processed to the server 104. After receiving the basic data for decomposing the optical mode to be processed, for the basic data for decomposing the optical mode to be processed, the server 104 uses the Finite Difference Time Domain (FDTD) method to establish a three-dimensional geometric model of the complex medium structure; based on the three-dimensional geometric model, uses the finite difference time domain method for numerical simulation to determine the electromagnetic field distribution information of the complex medium structure under the illumination of a special point light source; performs multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes; based on the multiple multipole modes, respectively determines the two-dimensional far-field radiation information of each multipole mode; merges the two-dimensional far-field radiation information of each multipole mode to obtain a comprehensive three-dimensional far-field radiation map. The server 104 can feedback the obtained comprehensive three-dimensional far-field radiation map to the terminal 102. In addition, in some embodiments, the method for decomposing the optical mode of the complex medium structure under a special point light source can also be implemented separately by the server 104 or the terminal 102. For example, the terminal 102 can directly perform optical mode decomposition processing on the basic data for decomposing the optical mode to be processed, or the server 104 can obtain the basic data for decomposing the optical mode to be processed from the data storage system and perform optical mode decomposition processing on the basic data for decomposing the optical mode to be processed.

[0052] Among them, the terminal 102 can be, but is not limited to, various desktop computers, laptop computers, smart phones, tablet computers, Internet of Things devices, and portable wearable devices. The Internet of Things devices can be smart speakers, smart TVs, smart air conditioners, smart in-vehicle devices, etc. The portable wearable devices can be smart watches, smart bracelets, head-mounted devices, etc. The server 104 can be implemented by an independent server or a server cluster composed of multiple servers, and can also be a cloud server.

[0053] In an exemplary embodiment, as Figure 2 shown, a method for decomposing the optical mode of a complex medium structure under a special point light source is provided. This method is executed by a computer device, and can specifically be executed separately by a computer device such as a terminal or a server, or jointly executed by a terminal and a server. In the embodiments of the present application, taking this method applied to Figure 1 the server 104 in it as an example for illustration, it includes the following steps S1 to step S5:

[0054] Step S1: Establish a three-dimensional geometric model of a complex dielectric structure using the finite-difference time-domain method.

[0055] In this embodiment, the complex dielectric structure includes silicon nanodisks with asymmetric notches.

[0056] Step S2: Based on the three-dimensional geometric model, perform numerical simulation using the finite-difference time-domain method to determine the electromagnetic field distribution information of the complex dielectric structure under the illumination of a special point source. Among them, the electromagnetic field distribution information includes the electric field information, refractive index information, coordinate information of different wavelengths of the special point source, and the scattering spectrum in each direction.

[0057] In this embodiment, the special point source is a dipole source.

[0058] In this embodiment, step S2 is based on the three-dimensional geometric model, and performs numerical simulation using the finite-difference time-domain method to determine the electromagnetic field distribution information of the complex dielectric structure under the illumination of a special point source, which specifically includes the following steps:

[0059] Based on the three-dimensional geometric model, perform numerical simulation using the finite-difference time-domain method. During the numerical simulation process, use a 3D monitor to obtain the electric field information, refractive index information, and coordinate information of different wavelengths of the special point source, and use a 2D monitor to obtain the scattering spectrum in each direction of the special point source.

[0060] Step S3: Perform multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes.

[0061] In this embodiment, the multipole modes include ED (Electric Dipole) mode, MD (Magnetic Dipole) mode, EQ (Electric Quadrupole) mode, MQ (Magnetic Quadrupole) mode, EO (Electric Octupole) mode, and MO (Magnetic Octupole) mode, etc.

[0062] In this embodiment, step S3 performs multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes, which specifically includes the following steps:

[0063] Import the electromagnetic field distribution information into calculation software, and use the calculation software to perform multi-level decomposition on the electromagnetic field distribution information to obtain ED mode, MD mode, EQ mode, MQ mode, EO mode, and MO mode, etc.

[0064] Step S4: Based on multiple multipole modes, respectively determine the two-dimensional far-field radiation information of each multipole mode.

[0065] In this embodiment, step S4 determines the two-dimensional far-field radiation information of each of the multiple multipole modes based on the multiple multipole modes, and specifically includes the following steps:

[0066] Step S41: Convert the Cartesian coordinate system to the spherical coordinate system.

[0067] Step S42: Calculate the two-dimensional far-field radiation patterns of each of the multiple multipole modes based on the spherical coordinate system.

[0068] Step S43: Determine the two-dimensional far-field radiation information of each of the multiple multipole modes according to the two-dimensional far-field radiation patterns of each of the multiple multipole modes.

[0069] Step S5: Combine the two-dimensional far-field radiation information of each of the multiple multipole modes to obtain a comprehensive three-dimensional far-field radiation pattern; the comprehensive three-dimensional far-field radiation pattern is used to characterize the optical properties of the complex dielectric structure under the illumination of the special point light source and reflect the contributions and interactions of each of the multiple multipole modes of the complex dielectric structure.

[0070] In this embodiment, step S5 combines the two-dimensional far-field radiation information of each of the multiple multipole modes to obtain a comprehensive three-dimensional far-field radiation pattern, and specifically includes the following steps:

[0071] Step S51: Combine the two-dimensional far-field radiation information of each of the multiple multipole modes in the order of the phi axis or the theta axis of the spherical coordinate system to obtain the two-dimensional far-field radiation information in the x-y plane of the entire three-dimensional space.

[0072] Step S52: Draw the three-dimensional far-field radiation patterns of each of the multiple multipole modes using drawing software according to the two-dimensional far-field radiation information in the x-y plane of the entire three-dimensional space.

[0073] Step S53: Draw the comprehensive three-dimensional far-field radiation pattern using drawing software according to the three-dimensional far-field radiation patterns of each of the multiple multipole modes.

[0074] In this embodiment, after step S5 combines the two-dimensional far-field radiation information of each of the multiple multipole modes to obtain a comprehensive three-dimensional far-field radiation pattern, the optical mode decomposition method of the complex dielectric structure under the special point light source further includes: Step S6: The verification step of the optical mode decomposition method of the complex dielectric structure under the special point light source, and specifically includes the following steps:

[0075] Step S61: Use a far-field calculation tool (Far field from closedbox) to obtain the three-dimensional far-field electric field information of the target wavelength.

[0076] Step S62: Generate a three-dimensional far-field radiation pattern based on a far-field calculation tool according to the three-dimensional far-field electric field information of the target wavelength.

[0077] Step S63: Compare the three-dimensional far-field radiation pattern based on the far-field calculation tool with the comprehensive three-dimensional far-field radiation pattern to verify the accuracy and reliability of the comprehensive three-dimensional far-field radiation pattern.

[0078] In this embodiment, by establishing a three-dimensional geometric model of a complex dielectric structure and combining the numerical simulation process of the finite-difference time-domain method, the interaction between the complex dielectric structure and the special point light source can be more realistically reflected, and the electromagnetic field distribution information of the complex dielectric structure under the illumination of the special point light source can be determined more accurately. Multiple multipole modes are obtained through multi-level decomposition, and then combined according to the two-dimensional far-field radiation information of each multipole mode to obtain a more accurate and reliable comprehensive three-dimensional far-field radiation pattern. Thus, the optical properties of the complex dielectric structure under the illumination of the special point light source can be effectively analyzed using this comprehensive three-dimensional far-field radiation pattern, accurately reflecting the contributions and interactions of the various multipole modes of the complex dielectric structure, and solving the problem that existing optical mode decomposition methods are difficult to accurately describe the contributions and interactions of the multipole modes of a complex dielectric structure under the illumination of a special point light source and cannot effectively analyze the optical properties of the complex dielectric structure under the illumination of a dipole source.

[0079] To make the technical solution of this embodiment clearer, the following takes an example to illustrate the specific implementation process of the technical solution of this embodiment in detail, including the following implementation steps:

[0080] Step S1: Use the finite-difference time-domain method to establish a three-dimensional geometric model of a complex dielectric structure, including a silicon nanodisk with an asymmetric notch, and determine the position, direction, and emission characteristics (frequency, polarization state) of the special point light source.

[0081] In this embodiment, in Step S1, numerical simulation is performed using the finite-difference time-domain method to establish a complex dielectric structure including, but not limited to, a silicon nanodisk, and an asymmetric design can be adopted. The special point light source is set as a dipole source. By adjusting the geometric parameters (x, y, z) of the dipole source, its position in three-dimensional space can be flexibly changed; by adjusting the theta parameter and the phi parameter, the direction of the dipole source can be precisely controlled; by adjusting the phase parameter, the polarization state of the dipole source can be changed, and generally, its wavelength range (broad wavelength or single wavelength) is adjusted to change its frequency. Among them, the theta parameter and the phi parameter are important parameters for describing the position of a point in the spherical coordinate system in three-dimensional space. The phase parameter is an instrument parameter of the dipole source.

[0082] In this embodiment, the three-dimensional geometric model of the complex dielectric structure is a silicon nanodisk with a notch and an asymmetric notch (height h = 300 nm, radius r = 130 nm, notch angle n = 150°), which is simply referred to as a notched silicon nanodisk. The special point light source is a dipole source, and the wavelength range of the special point light source is set to the visible light band (300 nm - 900 nm). It is placed 10 nm away from the structure on the positive x-axis along the z-axis direction (phase = 0, theta = 0, phi = 0). The forward (F) and backward (B) directions are the negative and positive x-axes, and the left (L) and right (R) directions are the negative and positive y-axes. Figure 3 It is a schematic structural diagram of the three-dimensional geometric model of the notched silicon nanodisk, showing the geometric structure (radius r, notch angle n, height h) of the notched silicon nanodisk and the defined directions (F / B / L / R).

[0083] Step S2: Based on the three-dimensional geometric model, the finite-difference time-domain method is used for numerical simulation to determine the electromagnetic field distribution information of the complex dielectric structure under the illumination of the special point light source. Among them, the electromagnetic field distribution information includes the electric field information, refractive index information, coordinate information of different wavelengths of the special point light source, and the scattering spectrum in each direction.

[0084] In this embodiment, the finite-difference time-domain method is used for numerical simulation to calculate the total electromagnetic field distribution of the complex dielectric structure under the illumination of the special point light source. The FDTD script language is written to obtain the electric field information, refractive index information, and coordinate information of different wavelengths from the 3D monitor, and store them as a Matlab file (Enxyzf.m); the scattering spectrum in each direction is obtained from the 2D monitor.

[0085] In this embodiment, the simulation region of the finite-difference time-domain method numerical simulation is defined as a cubic space of 1.5 μm * 1.5 μm * 1.5 μm, and all boundaries adopt a perfectly matched layer (PML) to eliminate the interference of boundary reflection on the simulation results. By using the finite-difference time-domain method for numerical simulation, the electromagnetic field distribution information of the complex dielectric structure under the illumination of the special point light source is calculated within the cubic space of 1.5 μm * 1.5 μm * 1.5 μm.

[0086] Among them, the 3D monitor can be a 3D discrete Fourier transform (DFT) monitor and a 3D refractive index monitor. By setting a 3D discrete Fourier transform monitor of 600 nm * 600 nm * 600 nm, it is used to record the electric field information (E x ,E y ,E z) Meanwhile, a 3D refractive index monitor of the same size is also set up to record the refractive index information (nx, ny, nz). An FDTD script is written to store its electric field information and refractive index information as a Matlab file (Enxyzf.m). In addition, for the 2D monitor, in this embodiment, a closed monitor (1000nm * 1000nm * 1000nm) composed of 6 2D discrete Fourier transform monitors is added, and this closed monitor is used to record the scattering spectra in each direction. Figure 4 It is the scattering spectrum diagram (600nm - 700nm) of the notched silicon nanodisk. It can be observed that the left and right scattering spectra reach the peak at 620nm, and the front and back scattering spectra reach the peak at 655nm. In this embodiment, the optical modes in the two bands of 620nm and 655nm are analyzed in detail.

[0087] Step S3: By inputting the required wavelength, use the calculation software (Matlab) to decompose Enxyzf.m into multiple multipole modes (ED mode, MD mode, EQ mode, MQ mode, EO mode, MO mode) through multi-level decomposition, and determine its contribution to the total scattering field.

[0088] In this embodiment, Enxyzf.m is imported into the Matlab software. By setting a number of wavelength points, the electric field data at specific wavelengths (620nm and 655nm) are read, and through multi-level decomposition, it is decomposed into ED(p0 + T2), MD(m1), EQ(Q 1αβ +Q 3αβ )、MQ(M 2αβ ), and determine its contribution to the total scattering field (C sca ). Figure 5 It is the mode decomposition diagram of the notched silicon nanodisk. The total scattering cross-section is expressed as:

[0089]

[0090] Among them, ε0 is the vacuum permittivity, ε d is the permittivity of the medium, k d is the wave number in the medium, k0 is the wave number in vacuum, v d is the speed of light in the surrounding medium, and μ0 is the vacuum permeability.

[0091] Step S4: Convert the Cartesian coordinate system (x, y, z) to the spherical coordinate system (r, phi, theta), and calculate the far-field radiation patterns of each multipole mode (ED mode, MD mode, EQ mode, MQ mode, EO mode, MO mode). The radiation pattern of each multipole mode provides the specific contribution of that multipole mode to the total radiation field (SUM). In the spherical coordinate system (r, phi, theta), two-dimensional far-field radiation information (in Excel format) of the x-y plane, x-z plane, and y-z plane can be obtained for each phi or theta respectively.

[0092] In this embodiment, in step S4, each multipole mode is correspondingly converted into the form of the far-field electric field through the Green's tensor, and the total scattered electric field contributed by each multipole mode is expressed as:

[0093]

[0094] where ε0 is the vacuum permittivity, k d is the wave number in the medium, k0 is the wave number in vacuum, v d is the speed of light in the surrounding medium, and n = r / r is the unit vector. Convert the electric field information (E x , E y , E z ) in the Cartesian coordinate system to the electric field information (E theta , E phi , E r ) in the spherical coordinate system. Among them, (E x , E y , E z ) represents the electric field components in the Cartesian coordinate system, and (E r , E phi , E theta ) represents the electric field components in the spherical coordinate system. E r is the component along the radial direction (r-direction), E theta is the component along the polar angle direction (theta-direction), and E phiis the component along the azimuthal direction (phi - direction). theta ranges from 0° to 180°, and phi ranges from 0° to 360°. By inputting its spherical coordinate coefficients (phi, theta), two - dimensional far - field radiation information can be obtained and stored in Excel format. The setting requirements for each plane are: x - y plane (phi = 0° - 360°, theta = 90°, Δphi = 10°), x - z plane (theta = 0° - 180°, phi = 0°, phi = 180°, Δtheta = 10°), y - z plane (theta = 0° - 180°, phi = 90°, phi = 270°, Δtheta = 10°). Calculate the far - field electric - field components of each multipole mode, and their superposition is the total far - field electric field. The coordinate transformation formula is:

[0095]

[0096] where pi represents the ratio of a circle's circumference to its diameter.

[0097] Step S5: By merging the two - dimensional far - field radiation information of each multipole mode in order (phi or theta) into an Excel file, and then using a plotting software to draw a comprehensive three - dimensional far - field radiation pattern. In this embodiment, the plotting software used is Origin plotting software.

[0098] In this embodiment, due to the introduction of the notch, the far - field radiation with origin symmetry in the three - dimensional space inside the structure is broken. Therefore, this embodiment needs to be analyzed from the perspective of the three - dimensional radiation pattern. By changing theta (0° - 180°, Δtheta = 10°, 1 * 37), two - dimensional far - field radiation information (19 * 37) of the x - y plane in the entire three - dimensional space is obtained. Each plane contains the far - field electric - field components of the multipole modes (ED mode, MD mode, EQ mode, MQ mode, EO mode, MO mode) and the total far - field electric - field component (SUM). Integrate all the plane information of each multipole mode into an Excel file, and then use Origin plotting software to draw a three - dimensional far - field distribution pattern of a single mode and a comprehensive three - dimensional far - field radiation pattern. Under the excitation of a dipole source, the two - dimensional far - field distribution pattern of a single mode often cannot fully reflect the true scattering characteristics. Through the three - dimensional far - field distribution pattern of a single mode, the spatial characteristics and direction dependence of each mode can be accurately captured, so as to truly reflect the optical response of the complex dielectric structure. The three - dimensional far - field distribution pattern of a single mode, by analyzing the changes of each mode, can deeply understand the scattering mechanism of the complex dielectric structure and its ability to control the light field. Accurately analyzing the changes of each mode is crucial for optimization design and application.

[0099] Figure 6The three-dimensional far-field distribution diagram of a single mode at 620 nm for a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°). Figure 7 The three-dimensional far-field distribution diagram of a single mode at 655 nm for a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°), where different colors represent different multipole modes. Figure 8 The comprehensive three-dimensional far-field radiation diagram at 620 nm for a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°). Figure 9 The comprehensive three-dimensional far-field radiation diagram at 655 nm for a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°). The comprehensive three-dimensional far-field radiation diagram is drawn by merging the two-dimensional far-field radiation information of each multipole mode. Therefore, the comprehensive three-dimensional far-field radiation diagram appears as one color as a whole. It can be seen that the three-dimensional far-field radiation intensity of a single mode is also consistent with that obtained by multipole decomposition. At 620 nm, ED resonantly couples with MD and EQ, and at 655 nm, ED resonantly couples with EQ and MQ.

[0100] Step S6: Add a far-field calculation tool in the FDTD script. After setting the analysis group theta, phi, and wavelength parameters through the script and running, the electric field information of the three-dimensional far-field at the target wavelength is saved as a Matlab file for plotting and compared with the comprehensive three-dimensional far-field radiation diagram obtained by this optical decomposition method to verify the accuracy and reliability of the multipole mode decomposition method.

[0101] In this embodiment, in step S6, a far-field calculation tool is added in the FDTD script. After setting the analysis group theta, phi, and wavelength parameters through the script and running, the three-dimensional far-field electric field information (E FDTD ) is stored as a plot in the form of a Matlab file and compared with the comprehensive three-dimensional far-field radiation diagram obtained by the method of this embodiment (E sum ) to verify the accuracy and reliability of the multipole mode decomposition method. The relative error calculation formula:

[0102]

[0103] where Error represents the relative error, E FDTD is the three-dimensional far-field electric field information based on the far-field calculation tool, and E sum is the far-field electric field data obtained by the method of this embodiment.

[0104] In this embodiment, the analysis group is set through the script (theta has 19 data and phi has 37 data) to obtain the three-dimensional far-field radiation diagrams at 620 nm and 655 nm. Figure 10The three-dimensional far-field radiation pattern of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 620 nm, based on a far-field calculation tool. Figure 11 The three-dimensional far-field radiation pattern of a notched silicon nanodisk (h = 300 nm, r = 130 nm, n = 150°) at 655 nm, based on a far-field calculation tool. In the three-dimensional far-field radiation pattern based on the far-field calculation tool, different colors represent different radiation intensities. In far-field calculations, color coding is usually used to represent the radiation intensity of electromagnetic waves. Specifically, the brighter the color (such as yellow or red), the higher the radiation intensity, while the darker the color (such as blue or green), the lower the radiation intensity, so that the distribution of the radiation intensity can be seen. In this embodiment Figure 10 and Figure 11 in, the radiation intensity in the yellow region is greater than that in the blue and green regions, and the radiation intensity in the green region is greater than that in the blue region. Therefore, the yellow, green, and blue regions show a gradual color change in the order of decreasing radiation intensity.

[0105] In this embodiment, the three-dimensional far-field radiation patterns based on the far-field calculation tool ( Figure 10 and Figure 11 ) are respectively compared with the comprehensive three-dimensional far-field radiation patterns obtained by the method of this embodiment ( Figure 8 and Figure 9 ). It can be observed that their radiation directions and radiation intensity distributions are consistent. Calculate the relative error between the far-field electric field information (three-dimensional far-field radiation pattern) based on the far-field calculation tool and the far-field electric field information (comprehensive three-dimensional far-field radiation pattern) obtained by the method of this embodiment. The calculation formula is as follows:

[0106]

[0107] It can be seen that the relative errors of the two different methods at 620 nm and 655 nm are 6.2% and 4.6% respectively, which indicates that the method in this embodiment has a relatively small relative error and has accuracy and reliability.

[0108] This embodiment particularly emphasizes the optical mode decomposition under a special point light source (such as a dipole source), which can more accurately simulate the light source conditions in actual application scenarios. By establishing a three-dimensional geometric model of complex dielectric structures such as silicon nanodisks with notch asymmetry design and combining with the numerical simulation process of the finite-difference time-domain method, the interaction between the structure and light can be more realistically reflected. By using Matlab software, the scattered field data is decomposed into multiple multipole modes through multi-level decomposition, and is transformed into far-field electric field components using the Green's tensor. This method can not only accurately describe the contributions of each multipole mode, but also transform them into far-field electric field components in the spherical coordinate system to plot a three-dimensional far-field radiation pattern, thereby determining their contributions to the total scattered electric field. This embodiment is not only applicable to special point light sources, but also can flexibly adjust the direction and frequency of the light source, and is applicable to different application scenarios. In addition, this method can be extended to other high refractive index dielectric nanostructures and has broad application prospects.

[0109] The present invention provides a method for optical mode decomposition of complex dielectric structures under a special point light source, which can accurately analyze and control the radiation direction and intensity distribution of multipole modes at different wavelengths. This method not only improves the understanding of the optical properties of complex dielectric structures, but also provides solid technical support for the development of new high-efficiency optical devices. By performing detailed geometric modeling, numerical simulation, multipole mode decomposition, and far-field radiation pattern generation on complex dielectric structures, this embodiment overcomes the limitations of the prior art and lays a foundation for the continuous innovation and development in the field of nanophotonics.

[0110] In an exemplary embodiment, a computer device is provided. The computer device can be a server or a terminal, and its internal structure diagram can be as Figure 12 shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O), and a communication interface. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the basic data of optical mode decomposition to be processed. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through a network connection. When the computer program is executed by the processor, it realizes a method for optical mode decomposition of complex dielectric structures under a special point light source.

[0111] Those skilled in the art can understand thatFigure 12 The structure shown is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0112] In an exemplary embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the steps in the above method embodiments are implemented.

[0113] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0114] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0115] Those of ordinary skill in the art can understand that all or part of the processes in the above method embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above method embodiments. Among them, any reference to a memory, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memories. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0116] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0117] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. An optical mode decomposition method for complex dielectric structures under a special point light source, characterized in that The optical mode decomposition method of a complex dielectric structure under a special point light source includes: Using the finite-difference time-domain method to establish a three-dimensional geometric model of the complex dielectric structure; Based on the three-dimensional geometric model, using the finite-difference time-domain method for numerical simulation to determine the electromagnetic field distribution information of the complex dielectric structure under the illumination of the special point light source; the electromagnetic field distribution information includes the electric field information, refractive index information, coordinate information of different wavelengths of the special point light source, and the scattering spectrum in each direction; Performing multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes; Based on multiple multipole modes, respectively determining the two-dimensional far-field radiation information of each multipole mode; Merging the two-dimensional far-field radiation information of each multipole mode to obtain a comprehensive three-dimensional far-field radiation map; the comprehensive three-dimensional far-field radiation map is used to characterize the optical properties of the complex dielectric structure under the illumination of the special point light source and reflect the contributions and interactions of each multipole mode of the complex dielectric structure.

2. The method for optical mode decomposition of a complex dielectric structure under a special point light source according to claim 1, wherein The complex dielectric structure includes a silicon nanodisk with an asymmetric notch, and the special point light source is a dipole source.

3. The optical mode decomposition method for complex dielectric structures under a special point light source according to claim 1, wherein Based on the three-dimensional geometric model, using the finite-difference time-domain method for numerical simulation to determine the electromagnetic field distribution information of the complex dielectric structure under the illumination of the special point light source, specifically including: Based on the three-dimensional geometric model, using the finite-difference time-domain method for numerical simulation. During the numerical simulation process, use a 3D monitor to obtain the electric field information, refractive index information, and coordinate information of different wavelengths of the special point light source, and use a 2D monitor to obtain the scattering spectrum in each direction of the special point light source.

4. The optical mode decomposition method for complex dielectric structures under a special point light source according to claim 1, wherein The multipole modes include ED mode, MD mode, EQ mode, MQ mode, EO mode, and MO mode; Performing multi-level decomposition on the electromagnetic field distribution information to obtain multiple multipole modes, specifically including: Importing the electromagnetic field distribution information into calculation software, and using the calculation software to perform multi-level decomposition on the electromagnetic field distribution information to obtain ED mode, MD mode, EQ mode, MQ mode, EO mode, and MO mode.

5. The optical mode decomposition method for complex dielectric structures under a special point light source according to claim 1, wherein Based on multiple multipole modes, respectively determining the two-dimensional far-field radiation information of each multipole mode, specifically including: Converting the Cartesian coordinate system to the spherical coordinate system; Based on the spherical coordinate system, respectively calculating the two-dimensional far-field radiation maps of each multipole mode; According to the two-dimensional far-field radiation maps of each multipole mode, determining the two-dimensional far-field radiation information of each multipole mode.

6. The method for optical mode decomposition of complex dielectric structures under a special point light source according to claim 5, wherein Merging the two-dimensional far-field radiation information of each multipole mode to obtain a comprehensive three-dimensional far-field radiation map, specifically including: Merging the two-dimensional far-field radiation information of each multipole mode in the order of the phi axis or theta axis of the spherical coordinate system to obtain the two-dimensional far-field radiation information in the x-y plane of the entire three-dimensional space; According to the two-dimensional far-field radiation information in the x-y plane of the entire three-dimensional space, using drawing software to draw the three-dimensional far-field radiation maps of each multipole mode; According to the three-dimensional far-field radiation maps of each multipole mode, using drawing software to draw the comprehensive three-dimensional far-field radiation map.

7. The optical mode decomposition method for complex dielectric structures under a special point light source according to claim 1, wherein After the step of combining the two-dimensional far-field radiation information of each of the multipole modes to obtain a comprehensive three-dimensional far-field radiation pattern, the optical mode decomposition method for a complex dielectric structure under a special point light source further includes: Using a far-field calculation tool, obtain the three-dimensional far-field electric field information of the target wavelength; Generate a three-dimensional far-field radiation pattern based on the far-field calculation tool according to the three-dimensional far-field electric field information of the target wavelength; Compare the three-dimensional far-field radiation pattern based on the far-field calculation tool with the comprehensive three-dimensional far-field radiation pattern to verify the accuracy and reliability of the comprehensive three-dimensional far-field radiation pattern.

8. A computer device, comprising: A memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the computer program to implement the optical mode decomposition method for a complex dielectric structure under a special point light source according to any one of claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the optical mode decomposition method for a complex dielectric structure under a special point light source according to any one of claims 1-7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the optical mode decomposition method for a complex dielectric structure under a special point light source according to any one of claims 1-7.

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