Broadband terahertz fingerprint detection sensor based on gradient metasurface

Abstract

The invention provides a broadband terahertz fingerprint detection sensor based on a gradient metasurface, and relates to specific molecular recognition and detection. The gradient metasurface array is integrated on the upper surface of the substrate; the gradient metasurface array comprises a plurality of micro antenna unit structures, and each micro antenna unit structure specifically comprises an equal-length metal microrod array and a gradient metal microrod array; the isometric metal micro-rod array comprises a plurality of isometric metal micro-rods which are arranged in parallel; the gradient metal micro-rod array comprises a plurality of gold micro-rods which are arranged in parallel and are gradually changed in length; and the plurality of metal micro-rods with gradually reduced lengths are inserted into the gaps formed by the plurality of metal micro-rods with equal lengths. The gradient metasurface provided by the invention shows extraordinary resonance density in a limited and small printing area, the metasurface which is operated on a wide spectrum at the same time is realized along with the increase of the complexity of a sample, abundant spectrum information can be obtained on the wide spectrum, and tiny differences in fingerprints can be analyzed and absorbed through narrow-band resonance.

Description

Technical Field

[0001] The present invention relates to the field of specific molecular recognition and detection, and in particular to a broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface. Background Art

[0002] Enhanced absorption spectroscopy has become a powerful technique for detecting characteristic absorption of molecules with strong sensitivity and specificity. Taking advantage of the local electromagnetic field enhancement characteristics of micro-nano photonic structures, the resonant frequency is designed to the terahertz band to cover the molecular vibration mode. Amino acids, lipids, and carbohydrates, as basic components of life, exhibit different spectral characteristics in the terahertz range due to different rotational and collective vibration frequencies. The enhanced light-matter interaction by this method is helpful for the detection of trace analytes, while the unique molecular absorption characteristics enable the extraction of chemical specific information from spectrally resolved measurements. In addition, for systems involving multiple molecular mixtures, distinguishing and monitoring the individual components of such heterogeneous mixtures is the goal of biosensing. Therefore, in order to distinguish different biomolecules in biological systems and analyze the complex interactions between molecules, it is crucial to develop new label-free sensing platforms.

[0003] In the prior art, in order to accurately detect the multi-fingerprint spectra of analytes, micro-nano structures that support multi-band spectral response are designed to achieve this function. Multi-band enhancement of the spectrum is achieved by utilizing self-similar structures, combining functionalized materials, and multi-region resonant gradient metasurfaces. The metasurface design is limited to sampling multiple spectral points in an infinite two-dimensional space. The resonant frequency depends on the unit cell with periodic arrangement and discrete changes in spatial parameters, which limits the continuous mapping from space to spectrum and makes it difficult to distinguish multiple analytes in real time. Therefore, how to design a biosensor that can achieve continuous spectral enhancement in a limited area has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art or related technology, and provides a broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface, which can simultaneously distinguish multiple analytes by enhancing the different characteristic vibrations of multiple biological molecules in heterogeneous biological samples.

[0005] The present invention is realized through the following technical scheme: a broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface, comprising: a substrate, made of a light-transmitting material with low absorption rate; a gradient metasurface array, integrated on the upper surface of the substrate; the gradient metasurface array comprises a plurality of micro-antenna unit structures, the micro-antenna unit structures specifically comprising an equal-length metal micro-rod array and a gradual gradient metal micro-rod array; the equal-length metal micro-rod array comprises a plurality of equal-length metal micro-rods arranged in parallel; the gradual gradient metal micro-rod array comprises a plurality of metal micro-rods with decreasing lengths arranged in parallel; the gradual gradient metal micro-rod array is cross-arranged with the equal-length metal micro-rod array so that the plurality of metal micro-rods with decreasing lengths are interspersed in the gaps formed by the plurality of equal-length metal micro-rods.

[0006] In this technical solution, the gradual gradient metasurface possessed by the micro-antenna unit structure exhibits extraordinary resonance density in a limited small printing area. As the complexity of the sample increases, a metasurface that can operate simultaneously on a wide spectrum is realized, which can obtain rich spectral information on a wide band, and can analyze small differences in absorption fingerprints through narrowband resonance. This is achieved by the continuous change of the unit cell parameters. Each submetallic structure supports an independent continuous domain bound state mode, which can be continuously excited in this non-periodic system. With 19 different structures, the spectral range of 0.9 THz is covered, and the structure is compact within the range of 400×125μm². The gradual gradient metasurface proposed by the present invention can distinguish multiple analytes simultaneously in real time by enhancing the different vibration fingerprints of multiple biomolecules in heterogeneous biological samples.

[0007] The broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention preferably also includes: a terahertz generation module, which is used to generate a terahertz light beam, which irradiates the material to be tested from above the gradient metasurface array, passes through the gradient metasurface array, and is transmitted from the bottom of the substrate; a terahertz signal detection module, which is used to receive and detect the transmitted terahertz signal to reflect the subtle changes of the metasurface covering the material to be tested in the terahertz transmission spectrum.

[0008] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the substrate is silicon, quartz, sapphire, polymethylpentene TPX or polyethylene.

[0009] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the period of the antenna long axis direction of a single micro-antenna unit structure is 400 μm, and the period along the direction perpendicular to the long axis is 125 μm.

[0010] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the gap between each metal micro-rod in the micro-antenna unit structure is 5 μm.

[0011] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the width of each metal microrod in the equal-length metal microrod array and the gradual gradient metal microrod array is 5 μm.

[0012] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the equal-length metal micro-rod array includes 20 equal-length metal micro-rods, and the length of each metal micro-rod is 110 μm.

[0013] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the gradual gradient metal microrod array includes 19 metal microrods with decreasing lengths, and the lengths are 93μm, 89μm, 85μm, 81μm, 77μm, 74μm, 71μm, 68μm, 65μm, 63μm, 61μm, 59μm, 57μm, 55μm, 53μm, 51μm, 50μm, 49μm, and 48μm, respectively.

[0014] According to the broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface provided by the present invention, preferably, the metal micro-rods are made of gold or silver.

[0015] The beneficial effects achieved by the present invention include at least: the gradual gradient metasurface proposed by the present invention exhibits an extraordinary resonance density in a limited small printing area. As the complexity of the sample increases, a metasurface that can operate simultaneously on a wide spectrum is realized, which can obtain rich spectral information on a wide band, and can resolve small differences in absorption fingerprints through narrowband resonance. In addition, compared with traditional photonic integrated devices, the metasurface-based device provided by the present invention has the advantages of miniaturization, broadband performance and controllable resolution. The present invention can solve the absorption fingerprint problem without the need for complex processes, frequency scanning or moving chips and mechanical parts, thus paving the way for the realization of sensitive, universal, miniaturized and robust terahertz spectroscopy equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the three-dimensional structure of a broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface according to an embodiment of the present invention is shown.

[0017] Figure 2 for Figure 1 main view.

[0018] Figure 3 A schematic diagram of the structure of a micro-antenna unit of a broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0019] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The concept of bound states in the continuum domain (BICs) has emerged as a powerful tool to promote high-quality factor resonators. Although optical modes exist in a continuous spectrum of radiative states, they are completely decoupled from the external environment in space. An ideal BIC exhibits perfect optical field localization within the system and cannot be excited from the far field due to the complete interruption of its coupling channel with the external environment. However, in practice, to gain the advantage of strong field enhancement, finite radiation losses are required. The creation of such leakage channels can be achieved by breaking the geometric symmetry of the system, thereby converting the BIC into a quasi-BIC with finite and high quality factor as required, thus enabling practical access to strong localized fields with high quality factors. The radiation losses can be precisely controlled and can therefore be conveniently tuned by the degree of asymmetry.

[0021] like Figure 1 , Figure 2 and Figure 3 As shown, an embodiment of the present invention discloses a broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface, comprising: a substrate made of a light-transmitting material with low absorption rate; a gradient metasurface array integrated on the upper surface of the substrate; the gradient metasurface array comprises a plurality of micro-antenna unit structures, the micro-antenna unit structures specifically comprising an equal-length metal micro-rod array and a gradual gradient metal micro-rod array; the equal-length metal micro-rod array comprises a plurality of equal-length metal micro-rods arranged in parallel; the gradual gradient metal micro-rod array comprises a plurality of parallel-arranged metal micro-rods with decreasing lengths; the gradual gradient metal micro-rod array is cross-arranged with the equal-length metal micro-rod array so that the plurality of metal micro-rods with decreasing lengths are interspersed in the gaps formed by the plurality of equal-length metal micro-rods.

[0022] In this embodiment, a unique new resonant design is used, which is based on a micro-antenna array (gradient metasurface array) that supports interfering resonances (derived from multiple quasi-bound states in the continuum), which facilitates the simultaneous detection of a wide range of molecular vibrational modes at multiple spectral points through near-field enhanced interactions. The gradient metasurface is formed by introducing changes in geometric parameters along the axis. The electric field polarization of the broadband excitation source is parallel to the long axis of the antenna. The resonant frequency is tuned over a continuous spectrum range. The resonant frequency covers a continuous spectrum mapping. The changes in the absorption spectra of multiple analytes can be enhanced simultaneously by arbitrarily designing gradient microstructures to promote broadband enhancement. The design is able to overlap the vibrations of the characteristic absorption bands of L-glutamate (L-Glu), γ-aminobutyric acid (GABA), and glutamine (Gln). The platform works stably and is able to detect dynamic changes in characteristic fingerprints in real time and perform quantitative identification with the help of machine learning in multi-analyte systems.

[0023] According to the above embodiment, preferably, it also includes: a terahertz generation module, which is used to generate a terahertz light beam, which irradiates the material to be tested from above the gradient metasurface array, passes through the gradient metasurface array, and is transmitted from the bottom of the substrate; a terahertz signal detection module, which is used to receive and detect the transmitted terahertz signal to reflect the subtle changes of the metasurface covering the material to be tested in the terahertz transmission spectrum.

[0024] According to the above embodiment, preferably, the substrate is silicon, quartz, sapphire, polymethylpentene TPX or polyethylene.

[0025] like Figure 3 As shown, another embodiment of the present invention also discloses a specific implementation of a micro-antenna unit structure, the period of the micro-antenna unit structure along the x direction is 400μm, the period along the y direction is 125μm, and the gap between each metal micro-rod is set to 5μm. There are 39 metal micro-rods from left to right; including 20 metal micro-rods of equal length of 110μm, with a width d of 5μm; 19 metal micro-rods of decreasing length are interspersed among the metal micro-rods of equal length, with lengths of 93μm, 89μm, 85μm, 81μm, 77μm, 74μm, 71μm, 68μm, 65μm, 63μm, 61μm, 59μm, 57μm, 55μm, 53μm, 51μm, 50μm, 49μm, 48μm, and the width is also 5μm.

[0026] In summary, the present invention makes full use of the flexibility provided by high-quality factor plasmon metasurfaces and proposes a gradient metasurface toolkit that can achieve ultra-wideband terahertz sensing, chemical-specific analyte identification, and different light-matter interaction mechanisms. Achieving resonance at a specific frequency may require more complex parameter settings. Nevertheless, compared with other complex metamaterial structures, this method is easier to design and manufacture, especially for realizing multi-spectral devices. The resonance position can be adjusted as needed by adjusting the length parameters of the designed structure. In summary, the resonance spectral width and the center frequency of the resonance peak in the sensor can be adjusted by changing the number and length of the structure in each structural unit, which provides advantages for studying sensors and other multi-spectral devices with simple structure and flexible adjustability. The gradient metasurface provided by the present invention can achieve spectral tuning with resonance field enhancement by gradually and continuously scaling the metasurface unit cell design in any physical dimension, thereby creating a metasurface with spatial resonance control.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface, characterized in that: include: a substrate, made of a light-transmitting material with low absorption; A gradient metasurface array integrated on the upper surface of the substrate; The gradient metasurface array includes a plurality of micro-antenna unit structures, and the micro-antenna unit structures specifically include an equal-length metal micro-rod array and a gradual gradient metal micro-rod array; The equal-length metal microrod array comprises a plurality of equal-length metal microrods arranged in parallel; The gradual gradient metal microrod array comprises a plurality of metal microrods of decreasing lengths arranged in parallel; The gradual gradient metal microrod array is cross-arranged with the equal-length metal microrod array, so that a plurality of metal microrods with decreasing lengths are interspersed in the gaps formed by a plurality of equal-length metal microrods.

2. The broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface according to claim 1 is characterized in that: Also includes: A terahertz generating module, used for generating a terahertz beam, wherein the terahertz beam irradiates the substance to be measured from above the gradient metasurface array, passes through the gradient metasurface array, and is transmitted out from the bottom of the substrate; The terahertz signal detection module is used to receive and detect the transmitted terahertz signal so as to reflect the subtle changes of the metasurface covered with the substance to be tested in the terahertz transmission spectrum.

3. The broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface according to claim 1 is characterized in that: The substrate is silicon, quartz, sapphire, polymethylpentene TPX or polyethylene.

4. The broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface according to claim 1 is characterized in that: The period of a single micro-antenna unit structure in the antenna long axis direction is 400 μm, and the period in the direction perpendicular to the long axis is 125 μm.

5. The broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface according to claim 1 is characterized in that: The gap between each metal micro-rod in the micro-antenna unit structure is 5 μm.

6. The broadband terahertz fingerprint detection sensor based on the gradual gradient metasurface according to claim 5 is characterized in that: The width of each metal microrod in the equal-length metal microrod array and the gradual gradient metal microrod array is 5 μm.

7. The broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface according to any one of claims 1 to 5, characterized in that: The equal-length metal microrod array includes 20 equal-length metal microrods, and the length of each metal microrod is 110 μm.

8. The broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface according to any one of claims 1 to 5, characterized in that: The gradient metal microrod array includes 19 metal microrods with decreasing lengths, and the lengths are 93μm, 89μm, 85μm, 81μm, 77μm, 74μm, 71μm, 68μm, 65μm, 63μm, 61μm, 59μm, 57μm, 55μm, 53μm, 51μm, 50μm, 49μm, and 48μm, respectively.

9. The broadband terahertz fingerprint detection sensor based on a gradual gradient metasurface according to any one of claims 1 to 5, characterized in that: The metal micro-rods are made of gold or silver.

Images