Infrared spectral imaging system and method of manufacture

Abstract

The present application relates to the technical field of infrared spectrum imaging, and particularly relates to an infrared spectrum imaging system based on a tunable pixelated metasurface enhancement and a preparation method, comprising infrared detector units, a dielectric layer, a pixelated metasurface array unit, a nanometer gap layer and a graphene layer arranged in sequence from bottom to top, wherein geometric structure parameters of the pixelated metasurface array unit are obtained by a genetic algorithm reverse design, and are used for realizing wave vector matching between a super-low-loss acoustic graphene plasmon mode and free space light; the resonator unit formed by the pixelated metasurface array unit, the nanometer gap layer and the graphene layer generates low-loss acoustic graphene plasmons with different resonance frequencies under excitation of infrared light waves, so as to realize narrow-band filtering of incident light waves in space and high-resolution spectrum modulation. The present application has the advantages of high integration, high sensitivity, wide working waveband, and realization of detection of various unknown trace molecules.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of infrared spectrum imaging, and particularly relates to an infrared spectrum imaging system based on tunable pixelated metasurface enhancement and a preparation method. BACKGROUND

[0002] In the major fields related to the national economy and people's livelihood such as food safety, biological medicine and environmental monitoring, there is an urgent need for on-site rapid detection of trace substances. Compared with the traditional laboratory sampling detection method, on-site rapid detection technology has great advantages such as real-time online, convenient and efficient, large detection capacity, and has become a research hotspot in the field of trace substance detection. Infrared spectrum technology can directly detect molecular vibration modes, has high "fingerprint" characteristics, does not need sample labeling, and is non-destructive in-situ detection, which has extremely important significance for solving the common problems in the above fields. However, the traditional infrared spectrum technology has always relied on laboratory instruments and equipment, which has the disadvantages of large size, heavy weight and high price, which greatly hinders the practical application of the technology in on-site rapid detection. The development of portable, lightweight and low-cost miniature infrared spectrum detection systems has become the mainstream trend in the field of on-site rapid detection. However, due to the limitation of optical diffraction limit, it is difficult to further improve the detection limit of miniature infrared spectrum systems. Therefore, in view of the great demand for on-site rapid detection, it is urgent to introduce new materials and develop new methods to realize high-sensitivity miniature infrared spectrum detection systems.

[0003] In recent years, the surface-enhanced infrared spectrum technology based on surface plasmon effect can localize infrared light around the detected molecules, greatly enhancing the interaction between light and molecules, and providing a new way for the development of high-sensitivity on-site rapid detection technology. Domestic and foreign researchers have carried out a lot of research work, mainly including two kinds of spectrum signal enhancement ideas of metal surface plasmon and graphene surface plasmon. Compared with metal surface plasmon, graphene surface plasmon has the unique advantages of strong electromagnetic localization ability, low propagation loss and dynamically adjustable resonance frequency in the infrared band, which breaks through the limitation of dynamic tuning of metal surface plasmon and provides an effective solution for the development of high-sensitivity infrared spectrum detection technology and miniature system.

[0004] Currently, graphene nanoribbons or graphene / one-dimensional gold nanometer grating composite structures are mainly used to excite graphene plasmon resonance, but nano patterning of graphene material will introduce a large number of impurities and defects, which will seriously reduce the quality of graphene, and make the graphene plasmon have the problems of large mode loss, large resonance peak linewidth and low quality factor. The combination of complete graphene and one-dimensional gold nanometer grating can effectively avoid this problem, but due to the limited relaxation time of the current graphene material growth and transfer process, it is difficult to further improve its quality factor, resulting in the current graphene surface plasmon enhanced infrared spectroscopy technology has the problems of low enhancement multiple and spectral resolution, which makes it still rely heavily on Fourier infrared spectrometer, and it is difficult to realize the miniaturization and light weight of the detection system. Therefore, it is urgent to develop a new method of graphene plasmon mode excitation and enhanced infrared spectrum detection with ultra-low loss, in order to realize a high-sensitivity miniaturized infrared spectrum detection system. SUMMARY

[0005] The purpose of the present application is to provide an infrared spectrum imaging system based on tunable pixelated metasurface enhancement and a preparation method, which has the advantages of high integration, high sensitivity, wide working waveband, and can realize the detection of various unknown trace molecules, etc., and can realize the on-site rapid detection of food safety, biological medicine, environmental monitoring and other major fields.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides an infrared spectrum imaging system based on tunable pixelated metasurface enhancement, which comprises, from bottom to top, an infrared detector unit, a dielectric layer, a pixelated metasurface array unit, a nanometer gap layer and a graphene layer, the surface edge of the graphene layer is arranged with a source electrode and a drain electrode, and the source electrode and the drain electrode are conducted through the graphene layer;

[0008] The pixelated metasurface array unit is obtained by metal deposition and micro-nano processing on the surface of the dielectric layer, the geometric structure parameters of the pixelated metasurface array unit are obtained by reverse design of genetic algorithm, which is used to realize the wave vector matching of ultra-low loss acoustic graphene plasmon mode and free space light, and the surface array of the pixelated metasurface array unit and the infrared detector unit are arranged corresponding to each other in space position;

[0009] The resonator unit formed by the pixelated metasurface array unit, the nanometer gap layer and the graphene layer produces low-loss acoustic graphene plasmons of different resonance frequencies under the excitation of infrared light waves, thereby narrowing the band filtering of incident light waves in space and realizing high-resolution spectral modulation.

[0010] In some embodiments, the pixelated metasurface array unit is a discrete pattern composed of pixel arrays in the transverse direction of the device. The specific pattern is determined by an array encoding composed of binary numbers, where "1" represents a deposited metal region and "0" represents an undeposited metal region. The array encoding is obtained by reverse design using a genetic algorithm, and there is a functional mapping relationship between the array encoding and the ultra-narrow linewidth resonance spectrum. The size and period of the pixelated metasurface array unit range from 0.1μm to 1μm, the thickness ranges from 20nm to 100nm, and the array range is 4×4, 8×8, and 16×16.

[0011] In some embodiments, an infrared laser source disposed above the graphene layer is also included, the wavelength range of which is set to 3μm~20μm.

[0012] In some embodiments, the thickness of the dielectric layer ranges from 100 nm to 500 nm, and the material is an infrared transparent material selected from Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe or SiO2.

[0013] In some embodiments, the thickness of the nano-interstitial layer (40) ranges from 1 to 10 nm, and the material is an infrared transparent material selected from Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe or SiO2.

[0014] In some embodiments, the detection array band of the infrared detector unit is 3μm to 20μm, and the infrared detector unit is selected from mercury cadmium telluride infrared detectors, superlattice infrared detectors, or pyroelectric infrared detectors.

[0015] Secondly, the present invention provides a method for fabricating an infrared spectral imaging system based on tunable pixelated metasurface enhancement, comprising the following steps:

[0016] S1, deposit a dielectric layer on the surface of the infrared detector unit;

[0017] S2, deposit a metal layer on the surface of the dielectric layer and form pixelated metasurface array units through an etching process;

[0018] S3, depositing a nano-interstitial layer on the surface of pixelated metasurface array units;

[0019] S4, prepare several layers of graphene film and transfer the several layers of graphene film sequentially onto the nano gap layer, and arrange the several layers of graphene film in a stacked manner to form a graphene layer.

[0020] S5, source and drain electrodes are prepared on the edge of the graphene layer surface to obtain the infrared spectral imaging system based on tunable pixelated metasurface enhancement described above in this application.

[0021] In some implementations, the array encoding of the geometric structure parameters of the pixelated metasurface array units in S2 is obtained by reverse design using a genetic algorithm, specifically including the following steps:

[0022] S21, Construct the function mapping relationship between the array encoding of pixelated metasurface array unit geometry and ultra-narrow linewidth excitation spectrum;

[0023] S22, determine the structural parameters and fitness function of the genetic algorithm based on the target ultra-narrow linewidth excitation spectrum;

[0024] S23, Initialize the population encoding, randomly generate a population encoding consisting of several binary numbers, which corresponds to the random geometric structure of the pixelated metasurface array unit;

[0025] S24, based on the function mapping relationship, determine the ultranarrow linewidth excitation spectra corresponding to several population codes;

[0026] S25, select individual codes that meet the preset fitness function value requirements from the population codes based on the fitness function, and delete individual codes that do not meet the preset fitness function value requirements;

[0027] S26. The selected individual codes are optimized by crossover and mutation operators to obtain a new generation of population codes. The new generation of population codes are then iteratively optimized until convergence, resulting in an array code of the geometric structure parameters of the pixelated metasurface array unit.

[0028] The beneficial effects of this invention are:

[0029] 1. The pixelated metasurface array unit, nano-gap layer, and graphene layer in the tunable pixelated metasurface-enhanced infrared spectral imaging system described in this invention collectively form a tunable pixelated metasurface nanoresonator. This resonator can achieve narrower plasmon resonance peaks than conventional graphene plasmon devices, enabling high-resolution spectral modulation in spatial location. Together, they form a tunable pixelated metasurface nanoresonator, which can generate low-loss surface plasmon resonance modes with different resonance frequencies under infrared light source excitation, thereby exciting ultra-narrow linewidth resonance peaks at different frequencies, thus achieving narrowband filtering in spatial location. Simultaneously, when the resonance spectral frequency is modulated to match the molecular resonance frequency, the local electromagnetic field intensity interacting with the measured molecular layer surges, indicating strong coupling between the measured molecular layer and the plasmon mode, thereby achieving a significant enhancement of the molecular infrared absorption spectral signal. Furthermore, by applying an external voltage between the graphene layer and the pixelated metasurface array units, the Fermi level of the graphene is adjusted, thereby dynamically controlling the surface plasmon resonance peak and achieving molecular enhancement detection over a wide wavelength range.

[0030] 2. The pixelated metasurface array units, nano-gap layers, and graphene layers described in this invention collectively form a tunable pixelated metasurface nanoresonator, which is vertically integrated with the area array structure of the infrared detector unit to obtain an infrared spectral imaging system. Each metasurface unit has a different initial resonant frequency, enabling it to cover a wide range of molecular fingerprint spectral information under the same voltage. By performing grayscale imaging on the spectral signal intensity of each detector unit, the image information of the molecular fingerprint spectrum under the current voltage can be obtained. Further changing the external voltage shifts the resonant frequency of each metasurface unit, thereby covering an even wider range of molecular fingerprint information. Compared to single-point tunable graphene plasmon resonance devices, this system can effectively broaden the system's operating wavelength, achieving full-spectrum enhanced detection of various molecules. In addition, this system does not rely on traditional optical interference structures, frequency scanning, and beam splitting components, exhibiting high integration and portability, and can be used for rapid on-site detection.

[0031] 3. This invention utilizes a genetic algorithm to reverse-engineer a pixelated metasurface array unit metasurface structure. Through algorithmic reverse design, a functional mapping relationship between tunable pixelated metasurfaces and ultra-narrow linewidth excitation spectra can be established, enabling automatic search and optimization of the target structure via computer-aided design. Compared to traditional artificially designed metasurfaces, this method directly targets ultra-narrow linewidth excitation spectra, reverse-engineering pixelated metasurface array structures with rich geometric diversity and degrees of freedom, thereby improving the device's quality factor and significantly increasing the mode energy of the local electromagnetic field between graphene and the pixelated metasurface. This method does not rely on design experience or trial-and-error optimization, overcoming the limitation of extremely low quality factors in graphene plasmonic devices excited by traditionally artificially designed metasurfaces.

[0032] 4. This invention can realize the integrated functions of spectral modulation, enhancement, detection and imaging. It has the advantages of high integration, high sensitivity, wide working band, and the ability to detect a variety of unknown trace molecules, and has broad application prospects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the infrared spectral imaging system based on tunable pixelated metasurface enhancement described in an embodiment of the present invention;

[0034] Figure 2 for Figure 1 A schematic diagram of the longitudinal section of region A in the middle;

[0035] Figure 3 This is a schematic diagram of the structure of the pixelated metasurface array unit in an embodiment of the present invention;

[0036] Figure 4 Schematic diagrams of pixelated metasurface array units with different encodings;

[0037] Figure 5 This is a schematic diagram of the fabrication method of the infrared spectral imaging system based on tunable pixelated metasurface enhancement described in this embodiment of the invention.

[0038] Figure 6 This is a schematic diagram comparing the surface plasmon resonance spectra excited by the traditional metal grating structure and the pixelated metasurface structure of the present invention.

[0039] Figure 7 This is a schematic diagram comparing the infrared absorption spectra of an infrared spectral imaging system with and without a molecular layer.

[0040] Figure 8 This is a schematic diagram illustrating the infrared absorption spectra and imaging information of different molecules using the tunable pixelated metasurface-enhanced infrared spectroscopy imaging system described in this embodiment of the invention.

[0041] In the figure, 10—infrared detector unit, 20—dielectric layer, 30—pixelated metasurface array unit, 40—nano gap layer, 50—graphene layer, 60—molecular layer to be measured, 70—source, 80—drain, 90—readout circuit, 100—light source. Detailed Implementation

[0042] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0043] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0044] Example 1, see Figure 1 and Figure 2As shown, an infrared spectral imaging system based on tunable pixelated metasurface enhancement includes, from bottom to top, an infrared detector unit 10, a dielectric layer 20, a pixelated metasurface array unit 30, a nano-gap layer 40, and a graphene layer 50. A source electrode 70 and a drain electrode 80 are arranged along the edge of the graphene layer 50, and the source electrode 70 and drain electrode 80 are electrically connected through the graphene layer 50. During testing, the analyte molecule is placed on the graphene layer 50 by spraying, spin-coating, or drop-coating to form a analyte molecule layer 60.

[0045] The pixelated metasurface array unit 30 is obtained by metal deposition and micro / nano fabrication on the surface of the dielectric layer 20. The geometric parameters of the pixelated metasurface array unit 30 are designed by reverse engineering using a genetic algorithm to achieve wave vector matching between ultra-low loss acoustic graphene plasmon modes and free space light. The pixelated metasurface array unit 30 and the area array on the surface of the infrared detector unit 10 are arranged in spatial correspondence with each other.

[0046] The resonator unit formed by the pixelated metasurface array unit 30, the nano gap layer 40, and the graphene layer 50 generates low-loss acoustic graphene plasmons with different resonant frequencies under infrared light excitation, thereby performing narrowband filtering of the incident light wave in space and realizing high-resolution spectral modulation.

[0047] The pixelated metasurface array unit 30, the nano-gap layer 40, and the graphene layer 50 in the tunable pixelated metasurface-enhanced infrared spectral imaging system described in this invention collectively form a tunable pixelated metasurface nanoresonator. This resonator can achieve narrower plasmon resonance peaks than conventional graphene plasmon devices, enabling high-resolution spectral modulation in spatial location. Together, they form a tunable pixelated metasurface nanoresonator, which can generate low-loss surface plasmon resonance modes with different resonance frequencies under infrared light source excitation, thereby exciting ultra-narrow linewidth resonance peaks at different frequencies, thus achieving narrowband filtering in spatial location. Simultaneously, when the resonance spectral frequency is modulated to match the molecular resonance frequency, the local electromagnetic field intensity interacting with the molecular layer 60 under test surges, indicating strong coupling between the molecular layer 60 and the plasmon mode, thereby achieving a significant enhancement of the molecular infrared absorption spectral signal. Furthermore, by applying an external voltage between the graphene layer 50 and the pixelated metasurface array unit 30, the Fermi level of the graphene is adjusted, thereby dynamically controlling the surface plasmon resonance peak and achieving molecular enhancement detection over a wide wavelength range.

[0048] This invention arranges the pixelated metasurface array unit 30 and the surface array of the infrared detector unit 10 in spatially corresponding positions to detect the spectral signal of each metasurface unit. The spectral signal intensity of each detector unit is then imaged in grayscale using an algorithm to obtain image information of the molecular enhanced infrared spectral signal. Different vibration signal intensities correspond to different pixel grayscale values. Furthermore, by changing the external voltage, the resonant frequency of each pixelated metasurface array unit 30 is shifted, changing the operating band of the system, thereby achieving full-spectrum enhanced detection of different molecular vibration signals.

[0049] The infrared spectral imaging system based on tunable pixelated metasurface enhancement described in this invention has advantages such as high integration, high sensitivity, wide operating band, and the ability to detect a variety of unknown trace molecules. It can be used for rapid on-site detection in major fields such as food safety, biomedicine, and environmental monitoring.

[0050] See Figure 2 As shown, the surface conductivity of the graphene layer 50 is further adjusted by applying an external voltage between the pixelated metasurface array unit 30 and the graphene layer 50. The adjustment range of the external voltage is -2 to 2V, which dynamically adjusts the surface plasmon resonance peak of the graphene layer in the infrared range of 4 to 18 μm.

[0051] As a preferred embodiment of this example, see Figure 1 As shown, the infrared spectral imaging system based on tunable pixelated metasurface enhancement also includes an infrared laser source 100 arranged above the graphene layer, the wavelength range of which is set to 3μm~20μm.

[0052] As a preferred embodiment of this example, see Figure 2 and Figure 3 As shown, the pixelated metasurface array unit presents a discrete pattern composed of pixel arrays along the transverse direction of the device. The specific pattern is determined by an array encoding composed of binary numbers, where "1" represents a deposited metal region and "0" represents an undeposited metal region. The array encoding is obtained through reverse design using a genetic algorithm, and there is a functional mapping relationship between the array encoding and the ultra-narrow linewidth resonance spectrum. The specific algorithm flow is as follows: First, the algorithm randomly generates an initial population encoding, corresponding to the random geometric structure of the metasurface. Next, the algorithm selects pixelated metasurface encoding information with high fitness function values ​​from the population encoding. Then, the individual encodings are optimized using crossover and mutation operators. After running the crossover and mutation operators, the new generation population is passed to the genetic algorithm for the next iteration of optimization, and the optimization process continues until convergence.

[0053] The pixelated metasurface array unit 30 has a size and period range of 0.1μm to 1μm, a thickness range of 20nm to 100nm, and an array range of 4×4, 8×8, and 16×16.

[0054] join Figure 4 The pixelated metasurface array unit 30 can adopt geometric structures with various encoded information, and the spectral characteristic parameters of the metasurface structure corresponding to different encoded information are different. The size and period range of these structures are 0.1μm~1μm, and the thickness ranges from 20~100nm. They can be prepared by photolithography techniques such as electron beam lithography, focused ion beam etching, ultraviolet lithography, and laser direct writing, combined with methods such as electron beam evaporation, magnetron sputtering, and thermal evaporation.

[0055] A pixelated metasurface array unit 30 was designed using a genetic algorithm. This algorithmic reverse design establishes a functional mapping between tunable pixelated metasurfaces and ultra-narrow linewidth excitation spectra, enabling automatic search and optimization of the target structure through computer-aided design. Compared to traditional artificially designed metasurfaces, this method directly targets ultra-narrow linewidth excitation spectra, reverse-designing pixelated metasurface array structures with rich geometric diversity and degrees of freedom. This improves the device's quality factor and significantly enhances the mode energy of the local electromagnetic field between graphene and the pixelated metasurface. This method eliminates the need for design experience and trial-and-error optimization, overcoming the limitation of extremely low quality factors in graphene plasmonic devices excited by traditionally artificially designed metasurfaces.

[0056] In a preferred embodiment of this invention, the dielectric layer 20 has a thickness ranging from 100 to 500 nm and is made of an infrared-transparent material selected from Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, or SiO2. The dielectric layer 20 serves to prevent direct contact between the pixelated metasurface array unit 30 and the infrared detector unit 10, thereby protecting the infrared detector unit 10.

[0057] In a preferred embodiment of this invention, the thickness of the nano-interstitial layer 40 ranges from 1 to 10 nm, and the material is an infrared-transparent material selected from Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, or SiO2. The nano-interstitial layer 40 is disposed between the graphene layer 50 and the pixelated metasurface array unit 30. By exciting the low-loss surface plasmon resonance mode of the graphene layer 50 through the pixelated metasurface array unit 30, a strong local electric field can be generated on the surface of the graphene layer 50. At this time, the molecular vibrational modes are strongly coupled with this strong local electric field, greatly enhancing the infrared absorption signal of the molecular layer 60 under test on the chip.

[0058] In a preferred embodiment of this invention, the detection array band range of the infrared detector unit 10 is set to 3μm~20μm, and the infrared detector unit 10 is selected from mercury cadmium telluride infrared detectors, superlattice infrared detectors, or pyroelectric infrared detectors.

[0059] Example 2, see Figure 5 As shown, a method for fabricating an infrared spectral imaging system based on tunable pixelated metasurface enhancement includes the following steps:

[0060] S1. An infrared detector unit 10 is fabricated by depositing a thin film of infrared-sensitive material using vacuum deposition, molecular beam epitaxy, or vacuum thermal evaporation. Then, a dielectric layer 20 is deposited on the surface of the infrared detector unit 10 using electron beam evaporation, atomic deposition, or molecular beam epitaxy.

[0061] S2, a metal layer is deposited on the surface of the dielectric layer 20, and pixelated metasurface array units 30 are formed by etching. Specifically, a metal layer is deposited on the surface of the dielectric layer 20 by means of electron beam evaporation or thermal evaporation, and the pixelated metasurface array units 30 are obtained by dry etching or liquid phase stripping of the electron beam exposure structure, and the pixelated metasurface array units 30 are used as gates.

[0062] S3, a nano-gap layer 40 is deposited on the surface of the pixelated metasurface array unit 30 by magnetron sputtering, electron beam evaporation or atomic deposition to achieve surface plasmon excitation and gate voltage regulation.

[0063] S4. Several layers of graphene film are prepared by mechanical exfoliation or chemical vapor deposition, and the several layers of graphene film are sequentially transferred to the nano gap layer 40 by dry or wet method. The several layers of graphene film are stacked to form graphene layer 50.

[0064] S5. Metal contact ohmic electrodes are prepared on graphene layer 50 by ultraviolet lithography, laser direct writing or electron beam evaporation, that is, source electrode 70 and drain electrode 60 are prepared on the edge of graphene surface, to obtain the infrared spectral imaging system based on tunable pixelated metasurface enhancement as described in any embodiment of Example 1.

[0065] like Figure 6 As shown, the array encoding of the geometric structure parameters of the pixelated metasurface array unit is obtained by reverse design using a genetic algorithm, specifically including the following steps:

[0066] S21, Construct the function mapping relationship between the array encoding of pixelated metasurface array unit geometry and ultra-narrow linewidth excitation spectrum;

[0067] S22, determine the structural parameters and fitness function of the genetic algorithm based on the target ultra-narrow linewidth excitation spectrum;

[0068] S23, Initialize the population encoding, randomly generate a population encoding consisting of several binary numbers, which corresponds to the random geometric structure of the pixelated metasurface array unit;

[0069] S24, based on the function mapping relationship, determine the ultranarrow linewidth excitation spectra corresponding to several population codes;

[0070] S25, select individual codes that meet the preset fitness function value requirements from the population codes based on the fitness function, and delete individual codes that do not meet the preset fitness function value requirements;

[0071] S26. The selected individual codes are optimized by crossover and mutation operators to obtain a new generation of population codes. The new generation of population codes are then iteratively optimized until convergence, resulting in an array code of the geometric structure parameters of the pixelated metasurface array unit.

[0072] like Figure 7 As shown, the tunable pixelated metasurface nanoresonator composed of the pixelated metasurface array unit, the nano-gap layer, and the graphene layer can generate low-loss graphene surface plasmons under infrared light excitation, thereby exciting an ultra-narrow linewidth resonant spectrum in the infrared region.

[0073] like Figure 8 As shown, when the spectral resonant frequency is tuned to match the molecular vibration absorption frequency, due to the strong coupling effect, the resonant spectrum at the molecular vibration absorption frequency undergoes destructive interference, thereby enhancing the infrared spectral signal of the molecular layer to be measured.

[0074] The implementation principle and expected effects of the present invention will be further explained below with reference to embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below, and those skilled in the art can implement it in different forms. The purpose of this specification is merely to help those skilled in the art to comprehensively understand the specific details of the present invention.

[0075] This embodiment takes a tunable pixelated metasurface-enhanced infrared spectroscopy imaging system based on an InAs / GaSb superlattice detector as an example. Its fabrication process specifically includes the following steps:

[0076] S1. An InAs / GaSb superlattice infrared detector, i.e., infrared detector unit 10, is prepared by molecular epitaxy and connected to an external circuit, i.e., readout circuit 90. An aluminum oxide dielectric layer, i.e., dielectric layer 20, with a thickness of about 200 nm is deposited on the surface of the infrared detector unit 10 by electron beam evaporation to protect the infrared detector unit 10.

[0077] S2, photoresist is spin-coated onto the surface of dielectric layer 20, and a pixelated metasurface array unit 30 structure contour mask is obtained through electron beam exposure and development. A gold layer with a thickness of approximately 50 nm, a period of 800 nm, a linewidth of 80 nm, and a metasurface unit size of 500 μm × 500 μm with an array number of 4 × 4 are deposited on the contour mask of the pixelated metasurface structure by electron beam evaporation. The photoresist is then removed by liquid phase lift-off to obtain the pixelated metasurface array unit 30. The pixelated metasurface array unit 30 is used as a gate material to control the Fermi level and carrier concentration of graphene.

[0078] S3, using atomic layer deposition, a thin layer of aluminum oxide with a thickness of about 5 nm is deposited on the pixelated metasurface array unit 3 to obtain a nano-interstitial layer 40.

[0079] S4. A single-layer graphene film with a thickness of 0.34 nm was grown on copper foil by chemical vapor deposition (CVD). Poly(methyl methacrylate) (PMMA) was used as a transfer agent to transfer the graphene film onto a thin layer of alumina. The transfer was performed four times to obtain four graphene films. The four graphene films together constituted graphene layer 50.

[0080] S5, gold source electrode 70 and drain electrode 80 are prepared on the surface of graphene layer 50 by ultraviolet light etching and electron beam evaporation.

[0081] The examples used three different biomolecules as probe molecules, which were prepared by spin-coating and drop-coating incubation on a detection chip. Figure 9 The transmission spectra and imaging information of three biomolecules were tested under different voltage conditions. As shown in the figure, for the 4×4 tunable pixelated metasurface-enhanced infrared spectroscopy imaging system, sixteen transmission spectra were obtained from sixteen detector units. The coupling between the vibrational modes of biomolecules and the plasmon resonance modes on the graphene surface caused concave peaks, the frequencies of which corresponded to the resonant frequencies of various vibrational modes of the biomolecules. When the external voltage was 0.5V, the ssDNA molecule showed peaks at 1240 cm⁻¹. -1 and 1080cm -1 The vibrational modes at the location are greatly enhanced. By imaging the spectral signal intensity detected by each detector unit, grayscale images corresponding to different vibrational signal intensities of the ssDNA molecule are obtained, thus achieving enhanced visualization and detection of the ssDNA molecule. When the applied voltage is adjusted from 0.5V to 1.2V, the sixteen transmission spectra of the tunable pixelated metasurface array undergo frequency shift, covering new detection bands, thereby obtaining the IgG biomolecule and L-Ascorbic acid biomolecule at 1575 cm⁻¹. -1 1665cm -1 1755cm -1 1691cm -1The spectral information and grayscale images of the vibrational modes at the specified locations were obtained, and the results were visualized. Among them, the enhancement effect of molecular vibrational modes was greatest when the plasmonic resonance mode was closest to the vibrational frequency of biomolecules. The calculated enhancement factor of the system for the infrared spectral signal of biomolecules could reach up to 120 times.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above embodiments, those skilled in the art should understand that the description and embodiments are only considered exemplary and various changes can be made in form and detail. The true scope and spirit of the present invention are defined by the claims.

Claims

1. An infrared spectral imaging system based on tunable pixelated metasurface enhancement, characterized in that: The device includes an infrared detector unit (10), a dielectric layer (20), a pixelated metasurface array unit (30), a nano gap layer (40), and a graphene layer (50) arranged sequentially from bottom to top. A source electrode (70) and a drain electrode (80) are arranged on the edge of the surface of the graphene layer (50), and the source electrode (70) and the drain electrode (80) are connected through the graphene layer (50). The pixelated metasurface array unit (30) is obtained by metal deposition and micro / nano processing on the surface of the dielectric layer (20). The geometric parameters of the pixelated metasurface array unit (30) are designed by reverse engineering using a genetic algorithm to achieve wave vector matching between ultra-low loss acoustic graphene plasmon modes and free space light. The pixelated metasurface array unit (30) and the surface array of the infrared detector unit (10) are arranged in spatial order corresponding to each other. The resonator unit formed by the pixelated metasurface array unit (30), the nano gap layer (40) and the graphene layer (50) generates low-loss acoustic graphene plasmons with different resonant frequencies under infrared light excitation, thereby performing narrowband filtering of the incident light wave in space and realizing high-resolution spectral modulation.

2. The infrared spectral imaging system based on tunable pixelated metasurface enhancement according to claim 1, characterized in that: The pixelated metasurface array unit (30) is a discrete pattern composed of pixel arrays in the transverse direction of the device. The specific pattern is determined by an array encoding composed of binary numbers, where "1" represents the deposited metal area and "0" represents the undeposited metal area. The array encoding is obtained through reverse design using a genetic algorithm, and there is a functional mapping relationship between the array encoding and the ultra-narrow linewidth resonance spectrum; The pixelated metasurface array unit (30) has a size and period range of 0.1μm to 1μm, a thickness range of 20nm to 100nm, and an array range of 4×4, 8×8, and 16×16.

3. The infrared spectral imaging system based on tunable pixelated metasurface enhancement according to claim 1, characterized in that: It also includes an infrared laser source (100) arranged above the graphene layer (50), the wavelength range of which is set to 3μm~20μm.

4. The infrared spectral imaging system based on tunable pixelated metasurface enhancement according to claim 1, characterized in that: The thickness of the dielectric layer (20) ranges from 100nm to 500nm, and the material is an infrared transparent material selected from Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe or SiO2.

5. The infrared spectral imaging system based on tunable pixelated metasurface enhancement according to claim 1, characterized in that: The thickness of the nano-interstitial layer (40) ranges from 1 to 10 nm, and the material is an infrared transparent material selected from Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe or SiO2.

6. The infrared spectral imaging system based on tunable pixelated metasurface enhancement according to claim 1, characterized in that: The detection array band range of the infrared detector unit (10) is 3μm~20μm. The infrared detector unit (10) is selected from mercury cadmium telluride infrared detector, superlattice infrared detector or pyroelectric infrared detector.

7. A method for fabricating an infrared spectral imaging system based on tunable pixelated metasurface enhancement, characterized in that, Includes the following steps: S1, deposit a dielectric layer (20) on the surface of the infrared detector unit (10). S2, deposit a metal layer on the surface of the dielectric layer (20) and form pixelated metasurface array units (30) by etching process. S3, deposit a nano gap layer (40) on the surface of the pixelated metasurface array unit (30). S4, several layers of graphene film are prepared and the several layers of graphene film are sequentially transferred to the nano gap layer (40), and the several layers of graphene film are stacked to form a graphene layer (50). S5, a source electrode (70) and a drain electrode (80) are prepared on the edge of the graphene layer (50) to obtain the infrared spectral imaging system based on tunable pixelated metasurface enhancement as described in any one of claims 1 to 6.

8. The method for fabricating an infrared spectral imaging system based on tunable pixelated metasurface enhancement according to claim 7, characterized in that, The array encoding of the geometric structure parameters of the pixelated metasurface array unit (30) in S2 is obtained by reverse design using a genetic algorithm, specifically including the following steps: S21, Construct the function mapping relationship between the array encoding of pixelated metasurface array unit geometry and ultra-narrow linewidth excitation spectrum; S22, determine the fitness function of the genetic algorithm based on the target ultra-narrow linewidth excitation spectrum; S23, randomly generate a group code consisting of several binary numbers, which corresponds to the random geometric structure of the pixelated metasurface array unit; S24, based on the function mapping relationship, determine the ultranarrow linewidth excitation spectra corresponding to several population codes; S25, select individual codes that meet the preset fitness function value requirements from the population codes based on the fitness function, and delete individual codes that do not meet the preset fitness function value requirements; S26. The selected individual codes are optimized by crossover and mutation operators to obtain a new generation of population codes. The new generation of population codes are then iteratively optimized until convergence, resulting in an array code of the geometric structure parameters of the pixelated metasurface array unit.

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