Metasurface spectrum modulator based on continuum quasi bound state and spectrum imaging system

Abstract

The invention discloses a metasurface spectrum modulator based on a continuum quasi bound state and a spectrum imaging system. The modulator is an all-dielectric metasurface made of a silicon material, and structural parameters of the modulator can be designed and optimized by comparing reconstructed image quality corresponding to different structural heights. In a high-efficiency short-wave infrared calculation spectrum imaging system, incident light carrying spectrum information of all spatial points of a target object is subjected to spectrum modulation through a metasurface spectrum modulator based on a continuum quasi-bound state according to a spatial position and then is compressed and sampled by a photoelectric detector, and a spectrum of each spatial point of the target object is reconstructed through an ADMM algorithm; and splicing is carried out according to the space point positions, and finally a space-spectrum three-dimensional data cube of the target object is obtained. The short-wave infrared spectral imaging method has high performability, and short-wave infrared spectral imaging with high spectral precision and wide wavelength range is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectral imaging, and in particular relates to a metasurface spectral modulator based on a continuum quasi-bound state and a high-efficiency short-wave infrared computational spectral imaging system having the spectral modulator. Background Art

[0002] Short-wave infrared spectral imaging technology can obtain spatial-spectral three-dimensional data cubes in the range of 0.9-1.7 μm. It is a new type of visual perception technology that surpasses human perception and is widely used in remote sensing, military, agriculture, medical and security fields. However, traditional short-wave infrared spectral imaging systems rely on large components, which limits miniaturization and portability. At the same time, in practical applications, there are problems such as large data volume, high redundancy, long acquisition time, and difficulty in balancing spatial and spectral resolution.

[0003] The computational spectral imaging system based on micro-nano photonic structures has the characteristics of compact structure, stable performance, no need for moving components and large components, and can achieve high spectral resolution and promote the miniaturization and integration of on-chip spectral imagers. The micro-nano spectral modulator used can be directly integrated into the photodetector pixels to facilitate rapid data acquisition. Combined with the computational reconstruction algorithm, the system can accurately decode spectral information and improve analysis efficiency. Therefore, the use of computational spectral imaging systems based on micro-nano structures to achieve miniaturized, low-cost, high-quality, and wide-imaging short-wave infrared spectral imaging has become a current research hotspot.

[0004] In computational spectral imaging systems based on micro-nano photonic structures, the response (transmittance, reflectance or absorptivity) of the spectral modulator is crucial to the reconstruction accuracy of the system. Micro-nano photonic spectral modulators with high spectral diversity in spectral response can provide better reconstruction quality and spectral resolution. Narrowband spectral modulators with sharp resonance peaks usually have lower correlation coefficients and are suitable for high spectral accuracy requirements; broadband spectral modulators provide a wider wavelength range, but may affect the spectral reconstruction accuracy. Therefore, in order to achieve short-wave infrared imaging with both high spectral accuracy and wide wavelength range, it is urgent to design a micro-nano photonic spectral modulator that combines the advantages of broadband and narrowband modulation, achieve high quality factor resonance while maintaining a flat response at other wavelengths, and balance the spectral range and reconstruction accuracy. Summary of the invention

[0005] The present invention proposes a metasurface spectral modulator based on a continuum quasi-bound state, and a computational spectral imaging system with the spectral modulator, which realizes high-quality reconstruction of short-wave infrared spectral images.

[0006] In a first aspect, the present invention provides a metasurface spectral modulator based on a continuum quasi-bound state, comprising:

[0007] A mirror-symmetrical double elliptical column array made of silicon material, wherein the double elliptical column array is located on a silicon dioxide substrate;

[0008] The size of the double elliptical cylinder array varies uniformly in the lateral direction, and the major axis, minor axis and period of the double elliptical cylinder are controlled by a lateral scale scaling factor;

[0009] The metasurface spectral modulator is designed to excite the continuum quasi-bound electric dipole mode (ED-QBIC) and magnetic dipole mode (MD-QBIC) and precisely control the resonant wavelength of the mode;

[0010] The metasurface spectral modulator is further designed to achieve coordinated modulation of narrowband and broadband spectral features to cover the resonance peaks within the complete spectral range.

[0011] In a second aspect, the present invention provides a method for designing a metasurface spectral modulator, the method comprising the following steps:

[0012] Step 1) selecting a mirror-symmetrical double elliptical cylinder as a basic structural unit of a metasurface spectrum modulator, wherein the double elliptical cylinder is made of silicon material and is located on a silicon dioxide substrate;

[0013] Step 2) determining the structural height, orientation angle, major axis, minor axis and period of the double elliptical cylinder as structural parameters;

[0014] Step 3) adjusting the major axis, minor axis and period in the structural parameters to control the resonant wavelength of the continuum quasi-bound state electric dipole mode and magnetic dipole mode by uniformly changing the lateral scale scaling factor;

[0015] Step 4) designing the double elliptical cylinder array to excite a continuum quasi-bound state resonance peak with a high quality factor, wherein the resonance peak covers the entire imaging spectral range;

[0016] Step 5) realizes the synergistic effect of narrow-band continuum quasi-bound state resonance and metasurface wide-spectrum resonance modulation in the non-continuum quasi-bound state action band to meet the requirements of wide working bandwidth and high spectral resolution.

[0017] In a third aspect, the present invention provides a short-wave infrared computational spectral imaging system, which uses the metasurface spectral modulator, and the metasurface spectral modulator is directly integrated into the imaging pixel of the photodetector; the photodetector is used to detect the light modulated by the metasurface spectral modulator; the system also includes a light source for irradiating the target object;

[0018] The system reconstructs the detected signals through the alternating direction multiplier algorithm (ADMM) to obtain the spectral information of each spatial point of the target object, and splices them according to the spatial position to finally obtain the spatial-spectral three-dimensional data cube of the target object.

[0019] Beneficial effects of the present invention:

[0020] (1) By directly integrating the continuum quasi-bound state metasurface spectral modulator into the imaging pixel of the detector, the data acquisition process is effectively simplified and the data sampling rate is improved, which is beneficial to reducing the size and cost of the short-wave infrared spectral imaging system.

[0021] (2) Short-wave infrared spectroscopy is achieved through a metasurface based on a continuum quasi-bound state. As the lateral scaling factor uniformly changes the scaling structure, the resonant wavelengths of ED-QBIC and MD-QBIC can be precisely controlled simultaneously. Through high-order resonances at large scaling factors, imaging in a larger spectral range and higher spectral resolution can be achieved.

[0022] (3) By realizing short-wave infrared spectral control through a metasurface based on a continuum quasi-bound state, the sparse characteristics of the target object in the spectral dimension are fully utilized, which greatly improves the sampling efficiency of the system and the reconstruction quality of the spectral image. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the short-wave infrared computational spectral imaging system of the present invention;

[0024] Figure 2 This is a flow chart for optimizing the double elliptical cylinder super surface in the present invention;

[0025] Figure 3 It is a basic structural schematic diagram of the metasurface spectral modulator based on the continuum quasi-bound state of the present invention;

[0026] Figure 4 These are the 25 spectral transmittances that can be achieved by the metasurface spectral modulator under the regulation of the scaling factor. DETAILED DESCRIPTION

[0027] The present invention is further described below with reference to the accompanying drawings and examples.

[0028] An embodiment of the present application provides a computational spectral imaging system for short-wave infrared (0.9-1.7 μm) with coordinated modulation of narrowband and broadband, including a light source, a metasurface spectral modulator based on a continuum quasi-bound state, and a photodetector.

[0029] The system compression sampling and calculation reconstruction process includes the following steps:

[0030] 1) The light source shines on the target object, generating incident light that carries the target's spatial-spectral information;

[0031] 2) The incident light carrying the spectral information of the target object is imaged according to the spatial position on the metasurface spectral modulator based on the continuum quasi-bound state integrated on the imaging pixel of the photodetector. The metasurface spectral modulator based on the continuum quasi-bound state numbers the incident light carrying the spatial point spectrum as Spectral modulation, L is the total number of modulations of the spectral modulator;

[0032] 3) The modulated light is directly detected by the photodetector;

[0033] 4) Input the detected signal into the ADMM algorithm for reconstruction to obtain the spectral information of the target spatial point;

[0034] 5) The reconstructed spatial point spectral information is spliced ​​according to the spatial position, and finally the spatial-spectral three-dimensional data cube of the target object is obtained.

[0035] In step 1), the incident light carrying the spatial-spectral information of the target object after discretization can be written as a vector form f, with a size of , where M is the size of the spectral dimension of the image to be reconstructed, is the size of the spatial dimension.

[0036] In step 2), the target object space point is carried The incident light spectral information can be written in vector form , the size is The total number of spectral modulations performed by the metasurface spectral modulator based on the continuum quasi-bound state is , corresponding to the metasurface The matrix form of spectral modulation is H, and the size is .

[0037] In step 3), the signal detected by the photodetector can be written as a vector g with a size of .

[0038] In step 4), the sparse prior used by the ADMM algorithm is Ψ, with a size of , is the number of atoms in the sparse prior.

[0039] In step 5), a spatial-spectral three-dimensional data cube of the target object is finally obtained, with a size of .

[0040] Preferably, the spectral dimension of the incident light at the spatial point is .

[0041] Preferably, the dynamic spectrum modulator modulates .

[0042] Preferably, a spatial-spectral 3D data cube of the target object .

[0043] The embodiments of the present application also provide an all-dielectric metasurface dynamic spectral modulator based on a continuum quasi-bound state and a method for optimizing its structural parameters.

[0044] The metasurface structure consists of a mirror-symmetrical double elliptical column array of silicon material on a silicon dioxide substrate. Silicon has low loss in the short-wave infrared region, and as the lateral scale scaling factor changes uniformly, the size of the double elliptical column also changes in the lateral direction.

[0045] By uniformly changing the lateral scale scaling factor and controlling the three structural parameters of the major axis, minor axis and period of a pair of basic double elliptical cylinders at the same time, the lateral size of the structure can be changed, and the resonance wavelengths of ED-QBIC and MD-QBIC can be precisely controlled at the same time, so that the high-quality factor continuum quasi-bound state resonance peaks excited by different double elliptical cylinder arrays cover the entire imaging spectral range; the narrow-band continuum quasi-bound state resonance and the metasurface wide-spectrum resonance modulation of the non-continuum quasi-bound state action band work together to achieve coordinated modulation of narrow-band and broadband spectral features in the complete spectral range, while meeting the requirements of wide working bandwidth and high spectral resolution.

[0046] The continuum quasi-bound state-based metasurface spectral modulator in the present application is directly integrated into the imaging pixel of the detector, and the 25 continuum quasi-bound state structures obtained by the scaling structure form the basic unit of spatial spectral modulation of a single pixel.

[0047] Furthermore, the metasurface parameter optimization is to optimize the structure height, so that the excitation position of the continuum quasi-bound state high quality factor resonance peak can cover the entire imaging band to obtain the best imaging effect. The specific optimization process includes the following steps:

[0048] 1) Select the structural parameters of the mirror-symmetric double elliptical cylinder based on the continuum quasi-bound state (including the major axis, minor axis, period, and orientation angle of the double elliptical cylinder). When the lateral scale scaling factor S=1, calculate the spectral transmittance of the metasurface based on the continuum quasi-bound state when the structure height varies from 300 nm to 600 nm through rigorous coupled wave analysis simulation, and record the transmittance matrix corresponding to different structure heights;

[0049] 2) By analyzing the excitation of the high quality factor resonance peak of the metasurface continuum quasi-bound state at different structural heights, the metasurface structure that can simultaneously excite ED-QBIC and MD-QBIC is screened;

[0050] 3) Through rigorous coupled wave analysis simulation, 25 spectral transmittances of the selected metasurface structures are calculated when S (0.52-1.48) changes uniformly, and the transmittance matrix of different structures is recorded;

[0051] 4) By analyzing the transmittance matrix recorded in step 3), the metasurface structure whose excited continuum quasi-bound state resonance peak can cover the entire short-wave infrared imaging band is screened;

[0052] 5) By evaluating the imaging quality of the metasurfaces selected in step 4) for a variety of real scenes, the structure with the highest average imaging quality is selected;

[0053] Preferably, the mirror-symmetric double elliptical cylinder has a fixed height of 500 nm, a fixed orientation angle of 40°, and a structure in which the major axis, minor axis, and period change uniformly with S. When S=1, the major axis is 452 nm, the minor axis is 266 nm, and the periods are 918 nm and 452 nm, respectively.

[0054] Example:

[0055] like Figure 1 As shown, the short-wave infrared computational spectral imaging system of this embodiment includes a light source 1, a metasurface spectral modulator 2 based on a continuum quasi-bound state, and a single-pixel detector 3.

[0056] The system sampling and reconstruction process includes:

[0057] 1) The light emitted by light source 1 is projected onto the target object. The target object is discretized into a three-dimensional data cube with a spatial size of 8*8 and a spectral size of 161. The spectral range is 900 nm-1700 nm, and the spectral interval is 5 nm;

[0058] 2) Each spatial point of the target object is imaged on the metasurface spectral modulator 2 based on the continuum quasi-bound state and numbered as Spectral modulation of

[0059] 3) The spectrum of each spatial point of the target object is modulated and directly detected by the photodetector 3;

[0060] 4) Reconstruct the short-wave infrared spectrum image of each spatial point of the target object through the ADMM algorithm;

[0061] 5) By splicing the spectrum of each spatial point according to the spatial position, a complete short-wave infrared spectrum image of the target object is finally obtained.

[0062] like Figure 2 As shown, the structural parameter optimization process of the metasurface spectral modulator based on the continuum quasi-bound state in this application is as follows:

[0063] 1) The long axis, short axis, period, and direction angle of the mirror-symmetric double cylinder of the metasurface based on the continuum quasi-bound state are selected. When S=1, the achievable spectral transmittance when the metasurface structure height varies in the range of 300 nm to 600 nm is calculated through rigorous coupled wave analysis simulation, and the corresponding spectral transmittance matrix is ​​recorded respectively, with a size of 1×161;

[0064] 2) Screening metasurface structures that can simultaneously excite ED-QBIC and MD-QBIC;

[0065] 3) Calculate the 25 spectral transmittances of each metasurface structure selected in step 2) when S changes uniformly in the range of 0.52 to 1.48 at an interval of 0.04 by rigorous coupled wave analysis, and record the spectral transmittance matrix H corresponding to different structures, with a size of 25×161;

[0066] 4) Screen out metasurface structures whose continuum quasi-bound state resonance peaks can cover the entire short-wave infrared imaging band;

[0067] 5) By imaging the metasurface selected in step 4) in a variety of real scenes and evaluating the imaging quality, the structure with the highest average imaging quality is selected.

[0068] like Figure 3 As shown in FIG. 1 , on a silicon dioxide substrate 32, after structural parameter optimization, the height of the mirror-symmetrical double elliptical cylinder 31 is fixed at 500 nm, the direction angle is fixed at 40°, and when S=1, the major axis is 452 nm, the minor axis is 266 nm, and the periods are 918 nm and 452 nm, respectively. By adjusting S to change uniformly from 0.52 to 1.48 at intervals of 0.04, 25 different transmission spectra can be achieved in the wavelength range of 900 nm-1700 nm in the short-wave infrared, see Figure 4 The excited high-quality factor continuum quasi-bound state resonance peak covers the entire imaging band, and works together with the metasurface wide-spectrum resonance modulation of the discontinuum quasi-bound state action band, thereby achieving the goal of coordinated modulation of narrow-band and broadband spectral features in the complete spectral range, and realizing short-wave infrared spectral imaging with both wide imaging band range and high spectral resolution.

[0069] The above description is only an example of a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A metasurface spectral modulator based on a continuum quasi-bound state, characterized in that: include: A mirror-symmetrical double elliptical column array made of silicon material, wherein the double elliptical column array is located on a silicon dioxide substrate; The size of the double elliptical cylinder array varies uniformly in the lateral direction, and the major axis, minor axis and period of the double elliptical cylinder are controlled by a lateral scale scaling factor; The metasurface spectral modulator is designed to excite continuum quasi-bound state electric dipole modes and magnetic dipole modes, and precisely control the resonant wavelength of the modes; The metasurface spectral modulator is further designed to achieve coordinated modulation of narrowband and broadband spectral features to cover the resonance peaks within the complete spectral range.

2. The metasurface spectral modulator according to claim 1, characterized in that: The double elliptical cylinder array includes 25 different size variations to achieve resonance peak coverage within the imaging spectral range.

3. The metasurface spectral modulator according to claim 1, characterized in that: The double elliptical column array of silicon material is fixed on a silicon dioxide substrate, and the height of the double elliptical column is fixed at 500 nm, and the direction angle is fixed at 40°.

4. The metasurface spectral modulator according to any one of claims 1 to 3, wherein: The metasurface spectral modulator is designed to operate in the short-wave infrared spectral range, with a wavelength range of 0.9-1.7 μm.

5. A method for designing a metasurface spectral modulator according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: Step 1) selecting a mirror-symmetrical double elliptical cylinder as a basic structural unit of a metasurface spectrum modulator, wherein the double elliptical cylinder is made of silicon material and is located on a silicon dioxide substrate; Step 2) determining the structural height, orientation angle, major axis, minor axis and period of the double elliptical cylinder as structural parameters; Step 3) adjusting the major axis, minor axis and period in the structural parameters to control the resonant wavelength of the continuum quasi-bound state electric dipole mode and magnetic dipole mode by uniformly changing the lateral scale scaling factor; Step 4) designing the double elliptical cylinder array to excite a continuum quasi-bound state resonance peak with a high quality factor, wherein the resonance peak covers the entire imaging spectral range; Step 5) realizes the synergistic effect of narrow-band continuum quasi-bound state resonance and discontinuum quasi-bound state action band metasurface wide-spectrum resonance modulation to meet the requirements of wide working bandwidth and high spectral resolution.

6. The design method according to claim 5, characterized in that: In step 3), the lateral scale scaling factor is uniformly varied in the range of 0.52 to 1.48 at an interval of 0.

04.

7. The design method according to claim 5 or 6, characterized in that: In step 5), the synergy is achieved by optimizing the structural height of the double elliptical cylinders to maximize the imaging quality and spectral resolution.

8. The design method according to claim 7, characterized in that: It also includes using rigorous coupled wave analysis simulation to calculate the spectral transmittance that can be achieved when the height of the structure changes.

9. The design method according to claim 7, characterized in that: It also includes an evaluation of the imaging quality of a variety of real scenes to select the metasurface structure with the highest average imaging quality.

10. A short-wave infrared computational spectral imaging system, using the metasurface spectral modulator described in any one of 1 to 4, characterized in that: The metasurface spectral modulator is directly integrated into the imaging pixel of the photodetector; the photodetector is used to detect the light modulated by the metasurface spectral modulator; the system also includes a light source for irradiating the target object; The system reconstructs the detected signals through an alternating direction multiplier algorithm to obtain the spectral information of each spatial point of the target object, and splices them according to the spatial position to finally obtain a spatial-spectral three-dimensional data cube of the target object.

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