Detection device and method based on stretchable metasurface-enhanced terahertz absorption spectroscopy

Abstract

The present invention discloses a detection device and method based on a stretchable metasurface-enhanced terahertz absorption spectroscopy. The detection device comprises a plurality of metasurface unit structures with identical parameters; each metasurface unit structure is composed of a dielectric substrate coated with a metal film. The coated metal film constitutes a metal microstructure, which is composed of an annular metal sheet and three metal strips located inside a metal frame. The thin film analyte to be measured is uniformly coated on the surface of the detection device. The detection device is dynamically stretched along the direction of the metal strip to change the width of the metasurface unit structure, thereby achieving geometric scanning and obtaining a series of resonant frequencies. Based on the SSP mode supported by the metal metasurface, the present invention can achieve broadband terahertz absorption spectrum enhancement of trace analytes. By connecting a series of resonant absorption peaks obtained by dynamically stretching the metal metasurface to form an envelope, an enhanced absorption spectrum can be established.

Description

Technical Field

[0001] The present invention belongs to the field of terahertz wave devices, and in particular relates to a detection device and method based on stretchable metasurface enhanced terahertz absorption spectroscopy. Background Art

[0002] Terahertz absorption spectroscopy shows great potential in many new applications, including biomedicine, gas sensing, and security detection. However, because traditional absorption spectroscopy measurement equipment causes terahertz wave diffraction, it usually requires the use of more materials, and the interaction distance between the terahertz wave and the sample may limit the necessary number of samples.

[0003] To improve the sensitivity of terahertz absorption spectroscopy, waveguides and metasurfaces have been explored in sensing applications. Terahertz dielectric waveguides offer advantages such as small measurement volume, long interaction length, and high signal-to-noise ratio. However, this hinders efficient direct coupling of terahertz waves into the waveguide. Furthermore, dielectric metagratings and metamaterial structures have been used to enhance broadband terahertz absorption spectra in thin-film samples. Generally, a series of resonance peaks can be obtained by varying the incident angle of the electromagnetic wave or by employing different unit cells in a metamaterial detection module. By linking a set of resonance peaks induced by the incident angle or unit cell geometry, the absorption rate of a thin-film sample can be significantly improved across a broad spectrum. Patent [202210775308.8] proposes a method using different metasurface geometries to construct a detection module using unit cells with varying metasurface structural parameters, thereby achieving geometric scanning. However, in practical experiments, scanning the incident angle at very small intervals is not easy to achieve, and it is difficult to precisely manufacture different unit cells with thicknesses of tens of microns and resolutions of a few microns. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of methods for measuring the terahertz absorption spectrum of trace amounts of analytes, as well as the difficulties and high costs of processing microstructures of varying sizes. To improve the efficiency of terahertz molecular fingerprint measurements, the present invention provides a detection device and method based on a stretchable metasurface-enhanced terahertz absorption spectrum. The present invention utilizes coated two-dimensional metal microstructures to excite terahertz artificial surface plasmons. Dynamically stretching the metal-coated dielectric substrate enables geometric multiplexing, causing the resonant frequency of a single metasurface unit structure to change, thereby generating a series of resonant absorption peaks of varying frequencies. By connecting the envelopes of these different resonant absorption peaks, an enhanced absorption spectrum can be obtained, significantly improving the precise, real-time monitoring of trace samples.

[0005] The specific technical solutions adopted in the present invention are as follows:

[0006] In a first aspect, the present invention provides a detection device based on stretchable metasurface enhanced terahertz absorption spectroscopy, which includes a periodic arrangement of a plurality of metasurface unit structures having the same structural parameters; each metasurface unit structure includes a dielectric substrate and a metal microstructure film coated on the surface of the dielectric substrate; the metal microstructure is composed of an annular metal sheet and three built-in metal strips; the annular metal sheet is rectangular in shape, the outer edge of which coincides with the outer edge of the upper surface of the annular metal sheet, the three built-in rectangular metal strips are arranged at equal intervals on the same long side of the inner ring of the annular metal sheet, and the positions on the upper surface of the dielectric substrate not covered by the annular metal sheet and the built-in rectangular metal strips remain exposed; the exposed portions of the dielectric substrate and the surface of the metal microstructure film are used to coat a thin film-like object to be tested;

[0007] The material and size of each metasurface unit structure are exactly the same. By dynamically stretching the dielectric substrate coated with a metal microstructure film along the width direction, the metasurface unit structures can have different resonant frequencies.

[0008] As a preference for the first aspect above, the dielectric material of the dielectric substrate is an organic polymer, including but not limited to polydimethylsiloxane, polyethylene or polytetrafluoroethylene.

[0009] As a preference of the first aspect above, the material of the metal microstructure film is gold, silver or copper.

[0010] As a preference of the first aspect above, the dielectric substrate has a length of 390 to 430 μm, a width of 130 to 170 μm, and a thickness of 30 to 70 μm.

[0011] As a preferred embodiment of the above-mentioned first aspect, in the metal microstructure film, the planar outline of the annular metal sheet is enclosed by an outer rectangle and an inner rectangle, the length of the outer rectangle is 390 to 430 μm, and the width is 130 to 170 μm, the length of the inner rectangle is 330 to 370 μm, and the width is 92.5 to 132.5 μm; the length of each built-in rectangular metal strip is 70 to 80 μm, and the width is 20 to 30 μm.

[0012] As a preferred embodiment of the above-mentioned first aspect, the detection device is composed of n×m metasurface unit structures periodically arranged in the form of a rectangular array, the metasurface unit structures in the detection device are completely consistent, and n and m are positive integers greater than 1.

[0013] As a preference for the first aspect above, the dielectric material of the dielectric substrate is preferably polydimethylsiloxane, with a relative dielectric constant of 2.35 and a loss tangent of 0.04.

[0014] As a preference of the first aspect above, the material of the metal microstructure film is preferably gold.

[0015] In a second aspect, the present invention provides a method for obtaining a lactose enhanced absorption spectrum using a detection device as described in any scheme of the first aspect, wherein the method comprises: coating the test substance lactose in the form of a thin film on the exposed portion of the upper surface of the dielectric substrate and the surface of the metal microstructure film, and vertically incidenting the terahertz wave on the top of the detection device to excite surface plasmons, and further calculating the absorption of the terahertz wave by detecting the reflection and transmission of the terahertz wave; dynamically and uniformly stretching the detection device causes the widths of the various metasurface unit structures constituting the detection device to change synchronously and uniformly, and recording a series of absorption spectra at different resonant frequencies corresponding to different widths during the change process; connecting the resonance peaks of the absorption spectra at different resonant frequencies to form an envelope to obtain the enhanced absorption spectrum of lactose.

[0016] As a preferred embodiment of the second aspect above, during the detection process, the width variation value of the metasurface unit structure used to form the absorption spectrum should cover a uniform sampling value within the range of 150 to 225 μm.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention, based on the SSP mode supported by a stretchable metal metasurface, can achieve broadband terahertz absorption spectral enhancement of trace analytes. By connecting the resonance peaks generated by a series of dynamically stretched metal metasurfaces to form an envelope, an enhanced absorption spectrum can be established. For example, using a 0.1 μm-thick lactose film, an absorption enhancement factor of approximately 270 times can be achieved within the ultra-broadband terahertz range. The designed structure for enhancing terahertz absorption of trace samples offers the advantages of ease of fabrication and measurement, providing a new approach for efficient terahertz fingerprint sensing using reconfigurable metamaterials in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the metasurface unit structure in a detection device based on stretchable metasurface-enhanced terahertz absorption spectroscopy;

[0020] Figure 2 Schematic diagram of the metal microstructure of the detection device;

[0021] Figure 3 is a planar schematic diagram of the detection device;

[0022] Figure 4 The electric field distribution diagram of the detection device when the dielectric substrate is stretched under the periodic boundary to excite the artificial surface plasmon on the metal grating structure. (ad) The metasurface is not coated with lactose film, and (eh) The metasurface is coated with lactose film.

[0023] Figure 5 The transmittance and reflectance of the detection device when no lactose film is coated under the periodic boundary, (a) transmittance, (b) reflectance;

[0024] Figure 6 The transmittance and reflectance of the detection device when the lactose film is coated under the periodic boundary, (a) transmittance, (b) reflectance;

[0025] Figure 7 The absorption rate of the detection device coated with 0.1um lactose under the periodic boundary is compared with that of the unenhanced 0.1um lactose film magnified 270 times.

[0026] The reference numerals in the figure are: lactose film 1, metal microstructure film 2, dielectric substrate 3. DETAILED DESCRIPTION

[0027] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention may be combined accordingly, provided that there is no conflict between them.

[0028] In a preferred embodiment of the present invention, a detection device based on stretchable metasurface enhanced terahertz absorption spectroscopy is provided. The detection module is composed of a periodic arrangement of metasurface unit structures, and a single metasurface unit structure is as follows: Figure 1 and Figure 2 As shown, the detection module formed by the periodic arrangement of the metasurface unit structure is as follows Figure 3 As shown in Figure 2, it is important to note that the detection module is composed of n×m metasurface unit structures arranged periodically in a rectangular array, with m units arranged horizontally and n units arranged vertically. The metasurface unit structures within the detection module are completely consistent. n and m are positive integers not less than 1, and their specific values ​​can be selected based on the actual required detection module size.

[0029] like Figure 1 and Figure 2 As shown, each metasurface unit structure consists of two parts: a lower layer, a dielectric substrate 3, and an upper layer, a metal microstructure film 2, which is applied and fixed to the surface of the dielectric substrate. The metal microstructure film 2 consists of an annular metal sheet and three internal metal strips. The annular metal sheet is rectangular, with its outer edge coinciding with the outer edge of the upper surface of the annular metal sheet. The three internal rectangular metal strips are evenly spaced along the same long side of the inner ring of the annular metal sheet. The upper surface of the dielectric substrate 3 not covered by the annular metal sheet and the internal rectangular metal strips remains exposed.

[0030] All n×n metasurface unit structures are continuously spliced ​​together on a plane to form a complete detection device. The substance to be detected can be coated on the metasurface formed by the splicing of the metasurface unit structures at the top of the detection device. The exposed portion of the dielectric substrate 3 and the surface of the metal microstructure film 2 in each metasurface unit structure are used to coat the thin film of the substance to be detected.

[0031] The material and size of each metasurface unit structure are exactly the same. By dynamically stretching the dielectric substrate 3 coated with the metal microstructure film 2 along the width direction, the entire device is deformed, so that the metasurface unit structure can have different resonant frequencies.

[0032] The above-mentioned detection device of the present invention utilizes a coated two-dimensional metal grating structure to excite terahertz artificial surface plasmons, and by stretching the gold-coated dielectric substrate, it can significantly enhance the accurate detection of trace samples. The present invention enhances the terahertz absorption spectrum by multiplexing the geometric parameters of the metal SSP metasurface. The specific geometric parameter adjusted is the width of the gold-coated dielectric substrate of the metasurface unit structure. In practical applications, a stretching device can be used to apply a balanced stretching force to different positions in the width direction of the detection device, thereby causing the metal microstructure film 2 and the dielectric substrate 3 to deform synchronously, thereby changing the width P of the detection device. y The value of will change the resonant frequency of the metasurface unit structure, thereby identifying trace ultrathin analytes by enhancing the envelope spectrum of a series of resonant absorption peaks.

[0033] Therefore, in the aforementioned detection device of the present invention, the materials and dimensions of each metasurface unit structure must remain identical. Stretching the width of the dielectric substrate with the metal film will result in different resonant frequencies in the detection module. Therefore, to accommodate stretching requirements, both the metal microstructure film 2 and the dielectric substrate 3 must possess a certain degree of ductility.

[0034] In this detection device, the materials and parameters of each component can be adopted as follows:

[0035] The dielectric substrate 3 is made of a low-loss, ductile dielectric such as polydimethylsiloxane, polyethylene, or polytetrafluoroethylene. The metal microstructure 2 is made of a ductile metal such as gold, silver, or copper. The dielectric substrate 3 has a length of 390-430 μm, a width of 130-170 μm, and a thickness of 30-70 μm. In the metal microstructure film 2, the planar outline of the annular metal sheet is formed by an outer rectangle and an inner rectangle. The outer rectangle has a length of 390-430 μm and a width of 130-170 μm, while the inner rectangle has a length of 330-370 μm and a width of 92.5-132.5 μm. Each inner rectangular metal strip has a length of 70-80 μm and a width of 20-30 μm. The spacing between adjacent inner rectangular metal strips is 75-115 μm, and the distance between the ends of the inner rectangular metal strips and the inner ring of the annular metal strip is 17.5-57.5 μm.

[0036] Correspond the above parameters to Figure 2 In the case of the relevant parameters, the range of values ​​is P x =390~430um, P y=130~170um, 3P=330~370um, d=17.5~57.5um, a=5~45um, W x =10~50um,W y =8.75~28.75um.

[0037] It should be noted that because the detection device of the present invention dynamically stretches the detection device along the metal strip to continuously change the width of the metasurface unit structure, achieving geometric scanning and obtaining a series of resonant frequencies, in order to ultimately obtain an enhanced absorption spectrum, the specific number of detection modules and the corresponding resonant frequencies of each detection module need to be optimized based on the spectrum required for detection and analysis of the object to be detected, so that the resonance peaks obtained by stretching can be connected to form an envelope, thereby establishing an enhanced absorption spectrum.

[0038] The method for obtaining the enhanced absorption spectrum of lactose using the above-mentioned detection device is as follows: the analyte lactose is coated in the form of a thin film on the exposed portion of the upper surface of the dielectric substrate 3 and the surface of the metal microstructure film 2. The terahertz wave is vertically incident on the top of the detection device and excites surface plasmons. The absorption of the terahertz wave is further calculated by detecting the reflection and transmission of the terahertz wave. The detection device is dynamically and uniformly stretched, causing the widths of the various metasurface unit structures constituting the detection device to synchronously and uniformly change. During the change process, the absorption spectra corresponding to a series of different resonant frequencies corresponding to different widths are recorded. The resonance peaks of the absorption spectra at different resonant frequencies are connected to form an envelope to obtain the enhanced absorption spectrum of lactose.

[0039] Preferably, during the detection process, the width variation value of the metasurface unit structure used to form the absorption spectrum should cover a uniform sampling value within the range of 150 to 225 μm.

[0040] The present invention is based on the SSP mode supported by the metal metasurface, which can realize the broadband terahertz absorption spectrum enhancement of trace analytes. By connecting a series of resonant absorption peaks obtained by dynamically stretching the metal metasurface to form an envelope, an enhanced absorption spectrum can be established.

[0041] The above-mentioned detection device based on stretchable metasurface enhanced terahertz absorption spectroscopy is applied to a specific example below to demonstrate its technical effect.

[0042] Example

[0043] In this embodiment, the detection device based on the stretchable metasurface enhanced terahertz absorption spectroscopy is composed of a 5×3 periodically arranged metasurface unit structure, and a single metasurface unit structure is as follows: Figure 1 and Figure 2As shown in Figure 1, each metasurface unit structure is divided into two parts: the lower layer is the dielectric substrate 3, and the upper layer is the metal microstructure film 2 coated on the surface of the dielectric substrate. The detection module formed by the periodic arrangement of the metasurface unit structure is shown in Figure 1. Figure 3 As shown. The specific structure of the detection device is as described above and will not be repeated here. However, the device parameters in this embodiment are as follows:

[0044] The dielectric material of dielectric substrate 3 is polydimethylsiloxane (PDMS), which has a relative dielectric constant of 2.35, a loss tangent of 0.04, and high transparency in the terahertz band. The material of metal microstructure 2 is gold, which has good ductility. The length P of dielectric substrate 3 is x is 410um, width P y is 150um, thickness t p In the metal microstructure film 2, the plane outline of the annular metal sheet is formed by the outer ring rectangle and the inner ring rectangle. The length of the outer ring rectangle is P. x is 410um, width P y is 150um, the length of the inner rectangle is 3P=(P x -2W x ) is 360um, width (P y -2W y ) is 112.5 μm. The length of each built-in rectangular metal sheet is 75 μm and the width a is 25 μm. The shortest distance d between one side of the rectangular metal sheet and the inner rectangle of the annular metal sheet is 37.5 μm, and the distance between adjacent built-in rectangular metal sheets is 95 μm. The thickness t of the dielectric substrate 3 is p 50um.

[0045] In order to obtain enhanced terahertz absorption spectrum, the width P can be changed by uniformly stretching the entire detection device along the width Py direction. y , so that the metasurface unit structure has different resonant frequencies. In this embodiment, control P y When the step size increases from 150um to 225um in 4.5um, a series of detection devices with different resonant frequencies are formed.

[0046] In this example, a 0.1 μm thick lactose film is used as the analyte. A 0.1 μm thick lactose film 1 is applied to the top metasurface of the metal microstructure 2. Lactose has a narrow linewidth resonance peak around 0.52 THz. SSPs are excited by a vertically incident terahertz wave directly incident on the coated two-dimensional metal microstructure metasurface 2. Figure 4 The electric field distribution diagram of artificial surface plasmons on the metal grating structure excited by the periodic boundary is shown before and after the metasurface of the detection device is coated with lactose film. Figure 5 As shown, when P yWhen the wavelength increases from 150 μm to 225 μm in steps of 4.5 μm, the resonance peak red-shifts, and the shifted resonance peaks of the transmission spectrum and the reflection spectrum each have the same amplitude.

[0047] In order to verify the excellent sensing performance of the metasurface, a 0.1 μm thick lactose film 1 was selected as a trace amount of analyte. Figure 6 As shown in Figure 1, based on the principle of geometric parameter reuse, a series of reflection and transmission spectra of the metasurface corresponding to different S are obtained. According to the formula A=1-RT, where A represents absorption, T represents transmittance, and R represents absorptivity, the corresponding absorption peak can be obtained. Figure 7 As shown, by connecting the resonance peaks of the absorption spectra excited by SSP corresponding to different S, an enhanced absorption spectrum of 0.1 μm thick lactose is formed. By comparison, the detection device and method proposed in the present invention can amplify the absorption spectrum of 0.1 μm lactose by 270 times.

[0048] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for acquiring lactose enhanced absorption spectrum using a detection device, characterized in that: The detection device is a detection device based on stretchable metasurface enhanced terahertz absorption spectroscopy, comprising a plurality of metasurface unit structures with the same structural parameters arranged periodically; each metasurface unit structure comprises a dielectric substrate (3) and a metal microstructure film (2) coated on the surface of the dielectric substrate (3); the metal microstructure film (2) is composed of an annular metal sheet and three built-in metal strips; the annular metal sheet is in a rectangular ring shape, the outer edge of which coincides with the outer edge of the upper surface of the annular metal sheet, and the three built-in rectangular metal strips are arranged at equal intervals on the same long side of the inner ring of the annular metal sheet The dielectric substrate (3) is a device for coating a thin film of a test object. ... The material and size of each metasurface unit structure are exactly the same, and by dynamically stretching the dielectric substrate (3) coated with the metal microstructure film (2) along the width direction, the metasurface unit structures can have different resonant frequencies; The method for obtaining a lactose enhanced absorption spectrum based on the detection device comprises: coating the test object lactose in the form of a thin film on the exposed portion of the upper surface of a dielectric substrate (3) and the surface of a metal microstructure film (2); vertically incident terahertz waves on the top of the detection device to excite surface plasmons; and further calculating the absorption of the terahertz waves by detecting the reflection and transmission of the terahertz waves; dynamically and uniformly stretching the detection device so that the widths of the various metasurface unit structures constituting the detection device are synchronously and uniformly changed, and recording a series of absorption spectra at different resonant frequencies corresponding to different widths during the change process; and connecting the resonance peaks of the absorption spectra at different resonant frequencies to form an envelope to obtain the enhanced absorption spectrum of lactose.

2. The method for obtaining lactose enhanced absorption spectrum according to claim 1, wherein: In the metal microstructure film (2), the plane outline of the annular metal sheet is formed by enclosing an outer ring rectangle and an inner ring rectangle, the outer ring rectangle has a length of 390 to 430 μm and a width of 130 to 170 μm, and the inner ring rectangle has a length of 330 to 370 μm and a width of 92.5 to 132.5 μm; each built-in rectangular metal strip has a length of 70 to 80 μm and a width of 20 to 30 μm.

3. The method for obtaining lactose enhanced absorption spectrum according to claim 1, wherein: The detection device is composed of n×m metasurface unit structures periodically arranged in the form of a rectangular array. The metasurface unit structures in the detection device are completely consistent, and n and m are positive integers greater than 1.

4. The method for obtaining lactose enhanced absorption spectrum according to claim 1, wherein: The dielectric material of the dielectric substrate (3) is preferably polydimethylsiloxane, with a relative dielectric constant of 2.35 and a loss tangent of 0.

04.

5. The method for obtaining lactose enhanced absorption spectrum according to claim 4, wherein: The material of the metal microstructure film (2) is preferably gold.

6. The method for obtaining lactose enhanced absorption spectrum according to claim 1, wherein: During the detection process, the width variation of the metasurface unit structure used to form the absorption spectrum should cover a uniform sampling value within the range of 150 to 225 μm.

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