Terahertz computer-generated hologram image processing method and system based on metasurface

Abstract

The invention discloses a processing method and system for a terahertz computer-generated hologram image based on a metasurface, and relates to the technical field of terahertz, and the processing method for the terahertz computer-generated hologram image based on the metasurface comprises the following steps: S1, constructing a terahertz reflection metasurface based on vanadium dioxide and photosensitive silicon; s2, calculating a hologram according to the required imaging data and the regulation and control characteristics of the terahertz wave of the constructed terahertz reflection metasurface, and loading the hologram to the constructed terahertz reflection metasurface to obtain a reflection terahertz wave; and S3, detecting and collecting reflected terahertz waves, and processing the reflected terahertz waves to obtain a reconstructed holographic image. The terahertz reflection metasurface is designed based on the silicon dioxide and the photosensitive silicon, the hologram is calculated based on the classical theory, efficient regulation and control of terahertz waves can be achieved, the algorithm complexity is reduced, and the calculation effect is improved.

Description

Technical Field

[0001] The present application relates to the field of terahertz technology, and in particular to a method and system for processing terahertz computer-generated holographic images based on a metasurface. Background Art

[0002] In the field of terahertz technology, the processing of terahertz computer-generated holographic images is of great significance for realizing applications such as high-resolution imaging, information storage and transmission. At present, the processing of traditional terahertz computer-generated holographic images faces many technical bottlenecks.

[0003] In terms of terahertz spatial light modulation, traditional terahertz spatial light modulators have problems with low modulation efficiency and insufficient resolution. Due to the limitations of their structure and material properties, it is difficult to flexibly and efficiently control the amplitude, phase and polarization state of terahertz waves, resulting in unsatisfactory imaging quality and failure to meet application requirements such as high-precision imaging.

[0004] At the level of holographic imaging algorithms, existing holographic imaging algorithms that rely on deep learning require a large amount of data for training, which not only consumes a lot of computing resources and increases computing and time costs, but also has poor interpretability. It is difficult to clearly understand the physical mechanism of the imaging process, which is not conducive to the optimization and improvement of the algorithm. Summary of the invention

[0005] The purpose of this application is to provide a method and system for processing terahertz computer-generated holographic images based on a metasurface, design a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon, and generate a hologram based on classical theory, which can achieve efficient control of terahertz waves, reduce algorithm complexity and improve calculation effect.

[0006] To achieve the above-mentioned purpose, the present application provides a method for processing terahertz computer-generated holographic images based on a metasurface, comprising the following steps: S1: constructing a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon; S2: calculating a hologram according to the required imaging data and the control characteristics of the terahertz wave of the constructed terahertz reflective metasurface, and loading the hologram into the constructed terahertz reflective metasurface to obtain a reflected terahertz wave; S3: detecting and collecting the reflected terahertz wave, processing the reflected terahertz wave, and obtaining a reconstructed holographic image.

[0007] As described above, the sub-steps of constructing a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon are as follows: S11: Obtain a vanadium dioxide parameter dataset and construct a vanadium dioxide dielectric constant model using the vanadium dioxide parameter dataset; S12: Obtain a photosensitive silicon parameter dataset and construct a conductivity and light parameter model of photosensitive silicon using the photosensitive silicon parameter dataset; S13: Obtain design requirement data, where the design requirement data includes at least: terahertz wave regulation target, external excitation conditions, structural parameter value range, and design target data; S14: Use the vanadium dioxide dielectric constant model, the conductivity and light parameter model of photosensitive silicon, and the design requirement data to obtain multiple sets of simulation input data, where each set of simulation input data includes at least: simulation material parameters and simulation structural parameters; S15: Input each set of simulation input data into electromagnetic simulation software to obtain multiple simulation results, and each simulation result includes at least: reflection coefficient, transmission coefficient, and phase change of terahertz wave; S16: Analyze each simulation result using the design target data to obtain multiple comprehensive errors, and use the comprehensive error threshold to judge each comprehensive error. If there is a comprehensive error less than or equal to the comprehensive error threshold, the simulation input data corresponding to the comprehensive error less than or equal to the comprehensive error threshold is used as the metasurface unit structure parameter, and a terahertz reflective metasurface is constructed according to the metasurface unit structure parameter; if all comprehensive errors are greater than the comprehensive error threshold, re-obtain the simulation input data and execute S15.

[0008] As described above, the expression of the comprehensive error is:

[0009] Wzh k = η1·|Sfs - Ffs k | + η2·|Sts - Fts k | + η3·|Sxw - Fxw k |; where, Wzh k is the comprehensive error between the k-th simulation result and the design target data; η1 is the error weight of the reflection coefficient of terahertz wave; Sfs is the reflection coefficient of terahertz wave in the design target data; Ffs k is the reflection coefficient of terahertz wave in the k-th simulation result; η2 is the error weight of the transmission coefficient; Sts is the transmission coefficient in the design target data; Fts k is the transmission coefficient in the k-th simulation result; η3 is the error weight of the phase; Sxw is the phase change in the design target data; Fxw k is the phase change in the k-th simulation result; η1 + η2 + η3 = 1.

[0010] As described above, wherein, the sub-steps of calculating the hologram according to the required imaging data and the terahertz wave modulation characteristics of the constructed terahertz reflection metasurface are as follows: S21: Process the required imaging data to obtain the target complex amplitude distribution; S22: Process the target complex amplitude distribution according to the terahertz wave modulation characteristics of the constructed terahertz reflection metasurface to obtain the optical field complex amplitude distribution; S23: Calculate the hologram according to the reference complex amplitude distribution and the optical field complex amplitude distribution.

[0011] As described above, wherein, the expression of the hologram is: I(x,y) = |U gc (x,y) + R(x,y)| 2 ; wherein, I(x,y) is the light intensity distribution at the point (x,y) of the hologram; U gc (x,y) is the optical field complex amplitude distribution at the point (x,y); R(x,y) is the reference complex amplitude distribution at the point (x,y).

[0012] As described above, wherein, the Fresnel diffraction theory is used to process the required imaging data to obtain the target complex amplitude distribution.

[0013] As described above, wherein, the sub-steps of processing the reflected terahertz wave to obtain the reconstructed holographic image are as follows: S31: Filter the reflected terahertz wave to obtain the filtered signal; S32: Amplify the filtered signal to obtain the amplified signal; S33: Process the amplified signal to obtain the reconstructed holographic image.

[0014] As described above, wherein, the Fourier transform is used to process the amplified signal to obtain the reconstructed holographic image.

[0015] As described above, wherein, the sub-steps of using the Fourier transform to process the amplified signal to obtain the reconstructed holographic image are as follows: T1: Perform a discrete Fourier transform on the amplified signal to obtain the frequency domain signal; T2: Perform an inverse Fourier transform on the frequency domain signal to obtain the reconstructed holographic image.

[0016] The present application also provides a processing system for terahertz computational holographic images based on metasurfaces, including: a metasurface design module, a hologram calculation module, a metasurface loading and wave modulation module, and an imaging and image processing module; among them, the metasurface design module: is used to construct a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon, determine the unit structure parameters of the terahertz reflective metasurface according to different functional requirements, and simulate and analyze the modulation performance of the terahertz reflective metasurface on terahertz waves; the hologram calculation module: is used to calculate the hologram according to the required imaging data and the modulation characteristics of the terahertz waves of the constructed terahertz reflective metasurface; the metasurface loading and wave modulation module: is used to load the hologram onto the constructed terahertz reflective metasurface, obtain the reflected terahertz waves, and realize the modulation of the incident terahertz waves; the imaging and image processing module: detects and collects the reflected terahertz waves, processes the reflected terahertz waves, and obtains the reconstructed holographic image.

[0017] The beneficial effects achieved by the present application are as follows:

[0018] (1) The processing method and system for terahertz computational holographic images based on metasurfaces in the present application construct a terahertz reflective metasurface based on vanadium dioxide (VO2) and photosensitive silicon, and can flexibly and efficiently modulate the amplitude, phase, and polarization state of terahertz waves, significantly improving the modulation effect and imaging resolution.

[0019] (2) The processing method and system for terahertz computational holographic images based on metasurfaces in the present application calculate the hologram based on classical theory, avoiding the complexity problems of deep learning algorithms, reducing the algorithm complexity, and improving the calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] 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 for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a schematic structural diagram of an embodiment of a processing system for terahertz computational holographic images based on metasurfaces;

[0022] Figure 2 It is a flowchart of an embodiment of a processing method for terahertz computational holographic images based on metasurfaces. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0024] As Figure 1 shown, the present application provides a processing system for terahertz computational holographic images based on a metasurface, including: a metasurface design module 1, a hologram calculation module 2, a metasurface loading and wave modulation module 3, and an imaging and image processing module 4.

[0025] Among them, the metasurface design module 1: is used to construct a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon, determine the unit structure parameters of the terahertz reflective metasurface according to different functional requirements, and simulate and analyze the modulation performance of the terahertz reflective metasurface on terahertz waves.

[0026] Specifically, different functional requirements include: holography, vortex, anomalous reflection, absorption, and focusing, but are not limited to holography, vortex, anomalous reflection, absorption, and focusing. According to functional requirements such as holography, vortex, anomalous reflection, absorption, and focusing, different characteristic metasurface unit structures are combined and arranged to obtain a metasurface with composite functions.

[0027] The hologram calculation module 2: is used to calculate a hologram according to the required imaging data and the modulation characteristics of the terahertz waves of the constructed terahertz reflective metasurface.

[0028] The metasurface loading and wave modulation module 3: is used to load the hologram onto the constructed terahertz reflective metasurface, obtain a reflected terahertz wave, and realize the modulation of the incident terahertz wave.

[0029] The imaging and image processing module 4: detects and collects the reflected terahertz wave, processes the reflected terahertz wave, and obtains a reconstructed holographic image.

[0030] As Figure 2 shown, the present application provides a processing method for terahertz computational holographic images based on a metasurface, including the following steps:

[0031] S1: Construct a terahertz reflective metasurface based on vanadium dioxide (VO2) and photosensitive silicon.

[0032] Furthermore, the sub-steps of constructing a terahertz reflective metasurface based on vanadium dioxide (VO2) and photosensitive silicon are as follows:

[0033] S11: Obtain a vanadium dioxide parameter dataset, and use the vanadium dioxide parameter dataset to construct a vanadium dioxide dielectric constant model.

[0034] Specifically, the vanadium dioxide parameter dataset includes multiple vanadium dioxide (VO2) sample data, and the multiple vanadium dioxide (VO2) sample data are parameter data of vanadium dioxide measured by acquisition devices (such as spectrometers and impedance analyzers) at different temperatures and different terahertz frequency bands, such as dielectric constant, conductivity, angular frequency, and damping coefficient.

[0035] Further, the expression of the vanadium dioxide dielectric constant model is:

[0036]

[0037] Among them, ε(T, ω) is the dielectric constant of vanadium dioxide (VO2) at temperature T and the angular frequency ω of the terahertz wave; ε ∞ is the dielectric constant at the high-frequency limit; ω p is the plasma oscillation angular frequency; j is an imaginary number, j 2 = 1; γ is the damping coefficient; f i is the oscillator strength of the i-th oscillator; ω pi is the plasma oscillation angular frequency of the i-th oscillator; ω 0i is the natural angular frequency of the i-th oscillator; γ i is the damping coefficient of the i-th oscillator; β(T, ω) is the coupling effect function of temperature and frequency.

[0038] Specifically, the vanadium dioxide dielectric constant model of the present application can accurately calculate the dielectric constant of vanadium dioxide considering the coupling effect of temperature and frequency, so as to more accurately predict the modulation performance of the metasurface on terahertz waves, and further optimize the unit structure parameters of the terahertz reflection metasurface.

[0039] Among them, the expression of the coupling effect function of temperature and frequency is:

[0040] β(T, ω) = A(T)·ω + B(T);

[0041] A(T) = a0 + a1T + a2T 2 ;

[0042] B(T) = b0 + b1T + b2T 2 ;

[0043] Among them, A(T) is the change data of the influence degree of the angular frequency ω of the terahertz wave on the coupling effect of temperature and frequency with respect to temperature T; B(T) is the change data of the influence degree of temperature T on the coupling effect of temperature and frequency except for the influence of the angular frequency ω of the terahertz wave; a0, a1, and a2 are the coefficient values of A(T), and b0, b1, and b2 are the coefficient values of B(T).

[0044] Specifically, A(T) and B(T) are obtained by fitting using specific research objects and experimental data. For example, the research object is vanadium dioxide (VO2), and the experimental data includes the transmission and reflection data of terahertz waves by vanadium dioxide (VO2) measured by terahertz time-domain spectroscopy technology at different temperatures to obtain dielectric constant data. The fitting method is used to fit the dielectric constant data, as well as the corresponding temperature and terahertz wave angular frequency, to determine the coefficient values (a0, a1, a2, and b0, b1, b2), thereby obtaining A(T) and B(T). Among them, the fitting method is preferably the least squares method, but is not limited to the least squares method.

[0045] S12: Obtain the photosensitive silicon parameter data set, and use the photosensitive silicon parameter data set to construct the conductivity and light illumination parameter model of the photosensitive silicon.

[0046] Specifically, the photosensitive silicon parameter data set includes multiple photosensitive silicon sample data, and the multiple photosensitive silicon sample data are the parameter data of the photosensitive silicon obtained by testing under different light illumination intensities and light wavelengths. For example: conductivity and carrier concentration changes.

[0047] Further, the expression of the conductivity and light illumination parameter model of the photosensitive silicon is:

[0048] σ Si (I,λ) = σ0 + Δσ(I,λ);

[0049] Among them, σ Si (I,λ) is the conductivity of the photosensitive silicon under the light illumination intensity I and the light wavelength λ; σ0 is the initial conductivity of the photosensitive silicon, that is: the conductivity without light illumination; Δσ is the change in conductivity caused by light illumination.

[0050] S13: Obtain the design requirement data, where the design requirement data includes at least: terahertz wave regulation target, external excitation conditions, structural parameter value range, and design target data.

[0051] Specifically, the terahertz wave regulation target is: to achieve continuous adjustment of the reflection phase from 0 to 2π within a preset frequency band or to achieve a preset polarization conversion efficiency. Among them, the specific value of the preset frequency band is set according to the actual situation. In this application, it is preferably: 0.1 - 1 THz. The specific value of the preset polarization conversion efficiency is set according to the actual situation. In this application, it is preferably: greater than 80%.

[0052] The external excitation conditions include: the working temperature range and working angular frequency range of vanadium dioxide (VO2), the light illumination intensity range and light wavelength of the photosensitive silicon.

[0053] The specific content and specific values of the structural parameter value ranges are set according to process limitations. For example: the shape of the patch unit, the size range of the patch unit, the minimum line width range, and the minimum spacing range. For example: the shape of the patch unit is rectangular, and the size range of the patch includes: the length range of the patch unit, the width range of the patch unit, and the thickness range of the patch unit.

[0054] The feasible region of the parameters is defined by external excitation conditions and process limitations to prevent the design from deviating from the actual application scenario.

[0055] The design target data is the ideal data determined according to the terahertz wave regulation target, including: the reflection coefficient, transmission coefficient, and phase change of the terahertz wave.

[0056] S14: Use the vanadium dioxide dielectric constant model, the conductivity of photosensitive silicon and the light parameter model, and the design requirement data to obtain multiple groups of simulation input data. Among them, each group of simulation input data includes at least: simulation material parameters and simulation structure parameters.

[0057] Furthermore, the sub-steps of using the vanadium dioxide dielectric constant model, the conductivity of photosensitive silicon and the light parameter model, and the design requirement data to obtain multiple groups of simulation input data are as follows:

[0058] S141: Construct multiple groups of vanadium dioxide input data according to the working temperature range and working angular frequency range in the external excitation conditions, and input each group of vanadium dioxide input data into the vanadium dioxide dielectric constant model to obtain multiple dielectric constants to be simulated; among them, each group of vanadium dioxide input data includes: a working temperature and a working angular frequency, the working temperature belongs to the working temperature range, and the working angular frequency belongs to the working angular frequency range.

[0059] S142: Construct multiple groups of photosensitive silicon input data according to the photosensitive silicon light intensity range and light wavelength in the external excitation conditions, and input each group of photosensitive silicon input data into the conductivity and light parameter model of photosensitive silicon to obtain multiple conductivity values to be simulated; among them, each group of photosensitive silicon input data includes: a photosensitive silicon light intensity and a light wavelength, and the photosensitive silicon light intensity belongs to the photosensitive silicon light intensity range.

[0060] S143: Construct multiple groups of structure parameters to be simulated according to the structural parameter value range. Among them, each group of simulation structure parameters includes at least: the shape of the patch unit, the size of the patch unit, the minimum line width, and the minimum spacing; among them, the size of the patch unit belongs to the size range of the patch unit, the minimum line width belongs to the minimum line width range, and the minimum spacing belongs to the minimum spacing range.

[0061] Specifically, for example: the shape of the patch unit is rectangular, and each set of simulation structure parameters includes at least: the minimum line width, the minimum spacing, the length of the patch unit, the width of the patch unit, and the thickness of the patch unit. The minimum line width belongs to the minimum line width range, the minimum spacing belongs to the minimum spacing range, the length of the patch unit belongs to the length range of the patch unit, the width of the patch unit belongs to the width range of the patch unit, and the thickness of the patch unit belongs to the thickness range of the patch unit.

[0062] S144: Construct multiple sets of simulation input data according to multiple dielectric constants to be simulated, multiple conductivity values to be simulated, and multiple sets of structure parameters to be simulated; wherein, each set of simulation input data includes: a dielectric constant to be simulated, a conductivity value to be simulated, and a set of structure parameters to be simulated.

[0063] S15: Input each set of simulation input data into electromagnetic simulation software to obtain multiple simulation results. Each simulation result includes at least: the reflection coefficient, transmission coefficient, and phase change of terahertz waves.

[0064] Further, the electromagnetic simulation software is CST (CST Microwave Studio) or HFSS (High-Frequency Structure Simulator), but is not limited to CST or HFSS, and can also be other electromagnetic simulation software that can achieve the functions required by this application.

[0065] S16: Analyze each simulation result using the design target data to obtain multiple comprehensive errors, and judge each comprehensive error using the comprehensive error threshold. If there is a comprehensive error less than or equal to the comprehensive error threshold, then use the simulation input data corresponding to the comprehensive error less than or equal to the comprehensive error threshold as the metasurface unit structure parameters, and construct a terahertz reflection metasurface according to the metasurface unit structure parameters; if all comprehensive errors are greater than the comprehensive error threshold, then re-obtain the simulation input data and execute S15.

[0066] Specifically, re-obtain the simulation input data through existing optimization methods, and obtain the optimal solution by gradually adjusting the structure parameters to be simulated. Among them, each time the structure parameters to be simulated are adjusted, the dielectric constant to be simulated and the conductivity value to be simulated need to be recalculated to ensure the accuracy of the simulation results. Among them, the optimization method is a genetic algorithm or a particle swarm optimization algorithm, but is not limited to the genetic algorithm or the particle swarm optimization algorithm.

[0067] Further, the expression of the comprehensive error is:

[0068] Wzh k = η1·|Sfs - Ffs k | + η2·|Sts - Fts k| + η3 · |Sxw - Fxw k |;

[0069] Among them, Wzh k is the comprehensive error between the k-th simulation result and the design target data; η1 is the error weight of the reflection coefficient of the terahertz wave; Sfs is the reflection coefficient of the terahertz wave in the design target data; Ffs k is the reflection coefficient of the terahertz wave in the k-th simulation result; η2 is the error weight of the transmission coefficient; Sts is the transmission coefficient in the design target data; Fts k is the transmission coefficient in the k-th simulation result; η3 is the error weight of the phase; Sxw is the phase change in the design target data; Fxw k is the phase change in the k-th simulation result; η1 + η2 + η3 = 1.

[0070] S2: Calculate the hologram according to the required imaging data and the terahertz wave modulation characteristics of the constructed terahertz reflection metasurface, and load the hologram onto the constructed terahertz reflection metasurface to obtain the reflected terahertz wave.

[0071] Furthermore, the sub-steps of calculating the hologram according to the required imaging data and the terahertz wave modulation characteristics of the constructed terahertz reflection metasurface are as follows:

[0072] S21: Process the required imaging data to obtain the target complex amplitude distribution.

[0073] Specifically, the required imaging data obtains the target complex amplitude distribution from the object plane to the hologram plane.

[0074] Furthermore, the Fresnel diffraction theory is used to process the required imaging data to obtain the target complex amplitude distribution, but it is not limited to the Fresnel diffraction theory.

[0075] S22: Process the target complex amplitude distribution according to the terahertz wave modulation characteristics of the constructed terahertz reflection metasurface to obtain the optical field complex amplitude distribution.

[0076] Specifically, the terahertz reflection metasurface realizes the modulation of the terahertz wave by changing its amplitude and phase. The terahertz wave modulation characteristics are related to the structural parameters and material properties. The target complex amplitude distribution is modulated by the terahertz reflection metasurface to obtain the optical field complex amplitude distribution.

[0077] Furthermore, the expression of the optical field complex amplitude distribution is:

[0078] U gc (x, y) = U mb (x, y) · H(x, y);

[0079] Among them, Ugc (x, y) is the complex amplitude distribution of the optical field at the point (x, y); U mb (x, y) is the complex amplitude distribution of the target at the point (x, y); H(x, y) is the modulation characteristic of the terahertz wave of the constructed terahertz reflection metasurface, which is used to represent the complex transmittance of the terahertz reflection metasurface at the point (x, y).

[0080] S23: Calculate the hologram according to the reference complex amplitude distribution and the complex amplitude distribution of the optical field.

[0081] Furthermore, the expression of the hologram is as follows:

[0082] I(x, y) = |U gc (x, y) + R(x, y)| 2 ;

[0083] where, I(x, y) is the light intensity distribution at the point (x, y) of the hologram; U gc (x, y) is the complex amplitude distribution of the optical field at the point (x, y); R(x, y) is the reference complex amplitude distribution at the point (x, y).

[0084] Among them, R(x, y) can be determined according to the experimental measurement method, the theoretical calculation method, the prior knowledge or the empirical model method.

[0085] S3: Detect and collect the reflected terahertz wave, process the reflected terahertz wave, and obtain the reconstructed holographic image.

[0086] Specifically, the reflected terahertz wave is detected and collected by a collection device. Among them, the collection device is a terahertz detector, but not limited to the terahertz detector.

[0087] Furthermore, the sub-steps of processing the reflected terahertz wave to obtain the reconstructed holographic image are as follows:

[0088] S31: Filter the reflected terahertz wave to obtain a filtered signal.

[0089] Furthermore, a digital filter is used to filter the reflected terahertz wave to obtain a filtered signal, but not limited to the digital filter. In this application, the digital filter is used to remove the noise and interference components doped in the signal and retain the effective signal related to the holographic image.

[0090] S32: Amplify the filtered signal to obtain an amplified signal.

[0091] Furthermore, an amplifier is used to amplify the filtered signal to obtain an amplified signal, but not limited to the amplifier. In this application, the amplifier is preferably used to enhance the amplitude of the signal for subsequent analysis and processing and improve the signal-to-noise ratio of the signal.

[0092] S33: Process the amplified signal to obtain the reconstructed holographic image.

[0093] Furthermore, the amplified signal is processed by using Fourier transform to obtain the reconstructed holographic image, but it is not limited to Fourier transform. Preferably, in this application, the amplified signal is transformed from the spatial domain to the frequency domain by Fourier transform for processing, so as to obtain the reconstructed holographic image.

[0094] Furthermore, the sub-steps of processing the amplified signal by using Fourier transform to obtain the reconstructed holographic image are as follows:

[0095] T1: Perform discrete Fourier transform on the amplified signal to obtain the frequency-domain signal.

[0096] T2: Perform inverse Fourier transform on the frequency-domain signal to obtain the reconstructed holographic image.

[0097] Furthermore, the expression of the reconstructed holographic image is:

[0098]

[0099] where Jcg(x, y) is the reconstructed holographic image at the point (x, y) of the hologram; IDFT2[] is the two-dimensional inverse discrete Fourier transform; z(n) is the time-domain signal; N is the total number of signal sampling points, n is the index of the discrete time series, used to identify each sampling point in the time-domain signal, and n ∈ [0, N - 1]; is the rotation factor, used to map the time-domain signal to the frequency domain; j is the imaginary number, j 2 = 1; e is the base of the exponential function; π is the pi; l is the discrete frequency index; is the frequency-domain signal.

[0100] The beneficial effects achieved by this application are as follows:

[0101] (1) The processing method and system of the terahertz computational holographic image based on metasurface in this application construct a terahertz reflective metasurface based on vanadium dioxide (VO2) and photosensitive silicon, which can flexibly and efficiently control the amplitude, phase and polarization state of terahertz waves, and significantly improve the modulation effect and imaging resolution.

[0102] (2) The processing method and system of the terahertz computational holographic image based on metasurface in this application calculate the hologram based on classical theory, avoid the complexity problem of deep learning algorithms, reduce the algorithm complexity, and improve the calculation efficiency.

[0103] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the protection scope of the present application is intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application. Obviously, those skilled in the art can make various changes and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the protection of the present application and the scope of equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A processing method for terahertz computer-generated holographic images based on metasurfaces, characterized in that It includes the following steps: S1: Construct a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon; S2: Calculate a hologram according to the required imaging data and the terahertz wave modulation characteristics of the constructed terahertz reflective metasurface, and load the hologram onto the constructed terahertz reflective metasurface to obtain a reflected terahertz wave; S3: Detect and collect the reflected terahertz wave, process the reflected terahertz wave, and obtain a reconstructed holographic image.

2. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 1, characterized in that, The sub-steps of constructing a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon are as follows: S11: Obtain a vanadium dioxide parameter data set, and use the vanadium dioxide parameter data set to construct a vanadium dioxide dielectric constant model; S12: Obtain a photosensitive silicon parameter data set, and use the photosensitive silicon parameter data set to construct a conductivity and light illumination parameter model of photosensitive silicon; S13: Obtain design requirement data, where the design requirement data at least includes: terahertz wave modulation target, external excitation conditions, structural parameter value range, and design target data; S14: Use the vanadium dioxide dielectric constant model, the conductivity and light illumination parameter model of photosensitive silicon, and the design requirement data to obtain multiple groups of simulation input data, where each group of simulation input data at least includes: simulation material parameters and simulation structural parameters; S15: Input each group of simulation input data into electromagnetic simulation software to obtain multiple simulation results, and each simulation result at least includes: reflection coefficient, transmission coefficient, and phase change of terahertz wave; S16: Analyze each simulation result using the design target data to obtain multiple comprehensive errors, and use the comprehensive error threshold to judge each comprehensive error. If there is a comprehensive error less than or equal to the comprehensive error threshold, then use the simulation input data corresponding to the comprehensive error less than or equal to the comprehensive error threshold as the metasurface unit structural parameters, and construct a terahertz reflective metasurface according to the metasurface unit structural parameters; if all comprehensive errors are greater than the comprehensive error threshold, then re-obtain the simulation input data and execute S15.

3. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 2, wherein The expression of the comprehensive error is: Wzh k = η1·|Sfs - Ffs k | + η2·|Sts - Fts k | + η3·|Sxw - Fxw k |; Among them, Wzh k is the comprehensive error between the k-th simulation result and the design target data; η1 is the error weight of the reflection coefficient of the terahertz wave; Sfs is the reflection coefficient of the terahertz wave in the design target data; Ffs k is the reflection coefficient of the terahertz wave in the k-th simulation result; η2 is the error weight of the transmission coefficient; Sts is the transmission coefficient in the design target data; Fts k is the transmission coefficient in the k-th simulation result; η3 is the error weight of the phase; Sxw is the phase change in the design target data; Fxw k is the phase change in the k-th simulation result; η1 + η2 + η3 = 1.

4. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 1, wherein The sub-steps of calculating a hologram according to the required imaging data and the terahertz wave modulation characteristics of the constructed terahertz reflective metasurface are as follows: S21: Process the required imaging data to obtain a target complex amplitude distribution; S22: Process the target complex amplitude distribution according to the terahertz wave modulation characteristics of the constructed terahertz reflective metasurface to obtain a light field complex amplitude distribution; S23: Calculate a hologram according to the reference complex amplitude distribution and the light field complex amplitude distribution.

5. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 4, wherein The expression of the hologram is: I(x,y) = |U gc (x,y) + R(x,y)| 2 ; Among them, I(x, y) is the light intensity distribution at the point (x, y) of the hologram; U gc (x, y) is the complex amplitude distribution of the light field at the point (x, y); R(x, y) is the reference complex amplitude distribution at the point (x, y).

6. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 4, characterized in that Use the Fresnel diffraction theory to process the required imaging data to obtain a target complex amplitude distribution.

7. The method for processing a terahertz computer-generated holographic image based on a metasurface according to claim 1, wherein The sub-steps of processing the reflected terahertz wave to obtain a reconstructed holographic image are as follows: S31: Filter the reflected terahertz wave to obtain a filtered signal; S32: Amplify the filtered signal to obtain an amplified signal; S33: Process the amplified signal to obtain a reconstructed holographic image.

8. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 7, wherein Use the Fourier transform to process the amplified signal to obtain a reconstructed holographic image.

9. The processing method of the metasurface-based terahertz computer-generated holographic image according to claim 8, characterized in that, The sub-steps of using the Fourier transform to process the amplified signal to obtain a reconstructed holographic image are as follows: T1: Perform a discrete Fourier transform on the amplified signal to obtain a frequency-domain signal; T2: Perform an inverse Fourier transform on the frequency-domain signal to obtain a reconstructed holographic image.

10. A processing system for terahertz computer-generated holographic images based on metasurfaces, characterized in that, It includes: A metasurface design module, a hologram calculation module, a metasurface loading and wave modulation module, and an imaging and image processing module; Among them, the metasurface design module: is used to construct a terahertz reflective metasurface based on vanadium dioxide and photosensitive silicon, determine the unit structure parameters of the terahertz reflective metasurface according to different functional requirements, and simulate and analyze the modulation performance of the terahertz reflective metasurface on terahertz waves; The hologram calculation module: is used to calculate the hologram according to the required imaging data and the terahertz wave modulation characteristics of the constructed terahertz reflective metasurface; The metasurface loading and wave modulation module: is used to load the hologram onto the constructed terahertz reflective metasurface, obtain a reflected terahertz wave, and realize the modulation of the incident terahertz wave; The imaging and image processing module: detects and collects the reflected terahertz wave, processes the reflected terahertz wave, and obtains a reconstructed holographic image.

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