Terahertz molecular fingerprint sensor based on over-coupling metasurface and electronic equipment

Abstract

The invention discloses a terahertz molecular fingerprint sensor based on an over-coupling metasurface and electronic equipment, and relates to the field of terahertz detection. Comprising fingerprint detection unit arrays which are periodically arranged and have the same structure; each fingerprint detection unit comprises a substrate layer, a first metal layer and a protruding structure. The first metal layer is arranged above the substrate layer and has the same cross sectional area with the substrate layer; the protruding structure is arranged above the first metal layer, and the cross section area of the protruding structure is smaller than that of the first metal layer. When the terahertz molecular fingerprint sensor detects a to-be-detected sample, the target position of the first metal layer and the upper surface of the protruding structure are coated with the to-be-detected sample. Terahertz waves are set to vertically enter the over-coupling metasurface, the coupling state of the terahertz waves and the metasurface is changed by adjusting the size of the protruding structure, and qualitative and quantitative detection is carried out on a to-be-detected sample. According to the invention, only a single device is needed, single detection is carried out through a single incident signal, and broadband fingerprint detection and'one-device double-detection 'of a trace sample to be detected are realized.

Description

Technical Field

[0001] This application relates to the field of terahertz detection, and more specifically, to a terahertz molecular fingerprint sensor and electronic device based on an overcoupled metasurface. Background Technology

[0002] Terahertz detection technology based on molecular fingerprint spectroscopy is a new generation of non-destructive analytical method for material identification and quantification, with significant application prospects in fields such as biomedicine, national defense and security, and environmental monitoring. However, terahertz wavelengths are typically on the order of hundreds of micrometers, which is significantly mismatched with the characteristic scale of most analytes (such as small molecules, pathogens, and pollutants). This size difference results in extremely weak interactions between terahertz waves and microscopic matter, limiting the sensitivity of traditional terahertz spectroscopy in trace detection applications and making it difficult to achieve high-precision identification and analysis.

[0003] To address these issues, metasurface-enhanced terahertz sensing technology has been proposed. This technology enhances the local electromagnetic field by introducing artificial micro / nano structures, thereby significantly increasing the interaction strength between terahertz waves and target molecules, enabling effective detection of trace molecules. However, existing metasurface sensors still face challenges in achieving simultaneous qualitative and quantitative detection of trace molecules due to conflicting physical mechanisms and high device complexity.

[0004] Therefore, there is an urgent need to propose a metasurface structure based on a novel resonance modulation mechanism to overcome the performance incompatibility between existing broadband and narrowband schemes, thereby achieving "dual detection with one instrument" for trace samples. Summary of the Invention

[0005] In view of the above problems, this application proposes a terahertz molecular fingerprint sensor and electronic device based on an overcoupled metasurface to overcome the shortcomings of the prior art.

[0006] This application provides a terahertz molecular fingerprint sensor based on an overcoupled metasurface, comprising: an array of fingerprint detection units of the same structure arranged periodically; each fingerprint detection unit includes: a substrate layer, a first metal layer, and a protrusion structure; The first metal layer is disposed above the substrate layer, and the two have equal cross-sectional areas; The protruding structure is arranged above the first metal layer, and its cross-sectional area is smaller than that of the first metal layer. When the terahertz molecular fingerprint sensor detects the sample to be tested, the sample to be tested is coated on the target position of the first metal layer and the upper surface of the protrusion structure. The target position refers to the position on the upper surface of the first metal layer that is not occupied by the protrusion structure. By setting a terahertz wave to be incident perpendicularly on the overcoupled metasurface and adjusting the volume of the protrusion structure to change the coupling state between the terahertz wave and the metasurface, the sample to be tested can be qualitatively and quantitatively detected.

[0007] Optionally, the protrusion structure includes: a dielectric layer and a second metal layer; The dielectric layer is disposed above the first metal layer, and the second metal layer is disposed above the dielectric layer; When the terahertz molecular fingerprint sensor detects the sample to be tested, the sample to be tested is coated on the upper surface of the second metal layer.

[0008] Optionally, when adjusting the volume of the protrusion structure, the thickness of the dielectric layer is changed first, while keeping the length and width of the dielectric layer and the size of the second metal layer unchanged; If changing the thickness of the dielectric layer cannot achieve the desired change in the coupling state, then the length and width of the dielectric layer and the second metal layer are further changed while keeping the thickness of the second metal layer constant.

[0009] Optionally, the shape of the protrusion structure can be arbitrary, but a cross shape is preferred.

[0010] Optionally, by adjusting the volume of the protruding structure, the coupling state between the terahertz wave and the metasurface is changed, so that the coupling state between the two changes from undercoupling to critical coupling and then to overcoupling, thereby stimulating the overcoupling effect and performing the qualitative and quantitative detection on the sample to be tested.

[0011] Optionally, the substrate layer may be made of silicon dioxide. The material of the first metal layer includes: gold.

[0012] Optionally, the material of the second metal layer includes: gold; The material of the dielectric layer includes: resin.

[0013] Optionally, the period of the substrate layer ranges from 75 μm to 110 μm; the thickness of the substrate layer is 200 μm; the period of the substrate layer determines the resonant frequency. The first metal layer and the second metal layer have the same thickness, both being 200 nm. The thickness of the dielectric layer ranges from 1 μm to 40 μm, the length of the dielectric layer ranges from 70 μm to 100 μm, and the width of the dielectric layer ranges from 1 μm to 5 μm. The thickness of the coating on the sample to be tested ranges from 1 μm to 5 μm.

[0014] Optionally, the specific values ​​of the period of the substrate layer, the specific values ​​of the thickness, length, and width of the dielectric layer, and the specific value of the coating thickness of the sample under test are determined by the frequency range of the fingerprint spectrum of the sample under test.

[0015] This application provides an electronic device, which includes: a terahertz molecular fingerprint sensor based on an overcoupled metasurface as described in any of the preceding claims.

[0016] This application proposes a terahertz molecular fingerprint sensor based on an overcoupled metasurface, comprising: an array of fingerprint detection units of the same structure arranged periodically; each fingerprint detection unit includes: a substrate layer, a first metal layer, and a protrusion structure. The first metal layer is disposed above the substrate layer, and the two have equal cross-sectional areas; the protrusion structure is disposed above the first metal layer, and its cross-sectional area is smaller than that of the first metal layer.

[0017] In this process, when a terahertz molecular fingerprint sensor detects a sample, the sample is coated onto a target location on the first metal layer and the upper surface of the raised structure. The target location refers to a position on the upper surface of the first metal layer that is not occupied by the raised structure; that is, the area where the raised structure connects to the first metal layer cannot be coated with the sample. By setting the terahertz wave to be perpendicularly incident on the overcoupled metasurface and adjusting the volume of the raised structure, the coupling state between the terahertz wave and the metasurface can be changed, thus enabling qualitative and quantitative detection of the sample.

[0018] This application innovatively proposes a novel overcoupled metasurface terahertz molecular fingerprint sensor based on the traditional metal-insulator-metal (MIM) resonator. By finely controlling the ratio of radiation loss to absorption loss in the resonant system to excite the overcoupling effect, a broadband enhanced resonant absorption peak can be formed with only a vertically incident terahertz wave excitation, thereby detecting broadband molecular fingerprint spectra under a single resonant signal.

[0019] The terahertz molecular fingerprint sensor of this application requires only a single device and performs a single detection using a single incident signal to achieve broadband fingerprint detection of trace samples. The entire process only requires loading the sample onto the terahertz molecular fingerprint sensor, without the need for additional sample processing. The detection method is convenient and has minimal impact on the sample. It enables simultaneous qualitative and quantitative detection of multiple trace samples, overcomes the performance incompatibility between existing broadband and narrowband solutions, and achieves "dual detection with one device" for trace samples. It has broad application prospects and high practicality. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a modular schematic diagram of each fingerprint detection unit in the embodiments of this application; Figure 2 This is a three-dimensional structural diagram of a fingerprint detection unit after coating the sample to be tested in an embodiment of this application; Figure 3 This is a top view schematic diagram of a preferred fingerprint detection unit after coating the sample to be tested in an embodiment of this application; Figure 4 This is a side view schematic diagram of a preferred fingerprint detection unit after coating the sample to be tested in an embodiment of this application; Figure 5 This is a coupling state curve diagram exemplified in the embodiments of this application; Figure 6 This is a schematic diagram of the electric field distribution at the resonance peak frequencies (frequency f=1.938THz, frequency f=1.976THz, frequency f=1.930THz) and at frequencies f=1.600THz and f=2.400THz under different coupling states in the embodiments of this application. Figure 7 This is a schematic diagram of the performance curve of the terahertz molecular fingerprint sensor when the sample to be tested is ε-HNIW in the embodiments of this application; Figure 8 This is a schematic diagram of the performance curve of the terahertz molecular fingerprint sensor when the sample to be tested is sucralose in the embodiments of this application. Detailed Implementation

[0021] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this application, and are merely some embodiments of this application, not all embodiments, and are not intended to limit this application.

[0022] Terahertz waves lie between the microwave and infrared regions of the electromagnetic spectrum, with a frequency range of approximately 0.1–10 THz. Many biochemical molecules exhibit characteristic rotational and vibrational modes in the terahertz band, allowing for non-destructive and specific "fingerprint" identification of molecules through their absorption spectra in this frequency range. This characteristic gives terahertz molecular fingerprint spectroscopy broad application prospects in fields such as biomedicine, food safety, environmental monitoring, and public safety.

[0023] However, the size of trace molecules is usually much smaller than the terahertz wavelength, making the interaction between light and matter extremely weak. This results in traditional terahertz spectroscopy having low sensitivity and poor resolution in trace detection, making it difficult to directly observe the absorption characteristics of the target.

[0024] The inventors discovered that, in order to improve the coupling efficiency between terahertz waves and trace samples, researchers have introduced metasurface structures (such as metal open rings, metal antennas, and dielectric gratings) to excite different electromagnetic resonance modes, including Fano resonance, guided mode resonance, ring dipole resonance, and quasi-bound states in the continuum (q-BIC). These resonance modes can significantly enhance the spectral signal of the target sample through a local near-field enhancement mechanism, thereby achieving highly sensitive trace substance detection.

[0025] The inventors further discovered that various enhancement strategies have been proposed to address the aforementioned problems, mainly categorized into broadband enhancement technology and narrowband enhancement technology. Among these, the main representative solutions for broadband enhancement technology include the following: 1) By utilizing a low-loss dielectric grating structure with a flat upper surface, a series of guided mode resonance modes are excited by terahertz waves incident from different angles below, generating an evanescent wave field on the upper surface, thereby achieving broadband absorption enhancement of trace samples such as lactose and tyrosine.

[0026] 2) By integrating the metal layer, polymer dielectric layer and periodic grating structure, and combining it with angle scanning technology, multi-angle response detection of various target substances (such as lactose, explosive molecules, etc.) is realized, thereby enabling the identification of different absorption peaks on a single structure.

[0027] 3) Introducing an upper and lower layer structure, the adjustable distance between the metallic metamaterial and the dielectric grating creates different coupling strengths, thereby changing the electric field distribution and achieving broadband transmission envelope control.

[0028] 4) Combining dual cross-aperture units of different sizes into multiple pixel arrays, with each pixel covering a specific terahertz frequency band, the combination enables coverage recognition of multi-molecule mixed signals.

[0029] 5) Introduce length gradient variations in the metal rod array to obtain continuously distributed high-density resonant modes and extend the bandwidth of the terahertz signal response.

[0030] However, the inventors discovered that the angle reuse method in the first technical solution above requires the introduction of a relatively complex detection device, making the detection process cumbersome. Furthermore, the enhancement effects between different angles are inconsistent, making accurate quantitative analysis impossible. Similarly, in the second technical solution, the angle reuse method requires the introduction of a relatively complex detection device, making the detection process cumbersome. Moreover, the enhancement effects between different angles are inconsistent, making accurate quantitative analysis impossible.

[0031] While the third technical solution improves the coverage of absorption peaks, it requires dynamic adjustment of the structural layer spacing, making operation complex and system integration difficult. Furthermore, the enhancement effects between different structures are inconsistent, hindering accurate quantitative analysis. The fourth technical solution requires a large number of reused structural pixels, making preparation complex and limiting detection speed. It is unsuitable for high-throughput real-time monitoring scenarios, and the enhancement effects between different pixels are also inconsistent, preventing accurate quantitative analysis. Although the fifth technical solution excels in broadband absorption enhancement, the uneven enhancement between different structures makes it difficult to achieve a uniform broadband enhancement effect, thus preventing accurate quantitative analysis.

[0032] For refractive index sensors that achieve high-sensitivity quantitative analysis based on narrowband enhancement technology, the main representative solutions include the following: 1) Utilizing an asymmetric capacitive-inductive coupled resonator to excite q-BIC resonance, achieving terahertz resonance. Q It exhibits an ultra-narrowband resonance response with values ​​exceeding 1000. This structure is extremely sensitive to biological samples at the nanomolar and even picomolar levels, significantly enhancing sensing sensitivity and facilitating the detection and differentiation of minute frequency shifts, thereby enabling highly sensitive quantitative analysis.

[0033] 2) A multi-resonance absorption structure was constructed using a metal split ring, achieving high absorption rates (96%+) and relatively high [missing information] at 1.1THz, 2.26THz, and 2.64THz. Q With a resonance peak value (up to 528), it can monitor refractive index changes at multiple frequency points, and is suitable for qualitative comparison and concentration analysis of different substances.

[0034] 3) By introducing a layer of polyimide onto a high-resistivity silicon substrate, the electromagnetic coupling capability of the metal structure is effectively improved, forming a single narrowband resonance peak at 0.704 THz. Q The value increased from 9.6 without polyimide to 15.2, and the sensitivity increased from 5.6 GHz / RIU to 12.9 GHz / RIU, demonstrating the effectiveness of fundamental mode enhancement in the low-frequency band.

[0035] However, the inventors discovered that in the first technical solution, because its sensor only supports narrowband resonant response, it is difficult to identify complex broadband fingerprint features and cannot directly perform qualitative analysis on trace samples. In the second technical solution, because each resonant response linewidth is extremely narrow, it is difficult to take into account the complex broadband fingerprint features of different substances, thus the device lacks specificity and versatility. In the third technical solution, because its sensor only supports narrowband resonant response, it is difficult to identify complex broadband fingerprint features and cannot directly perform qualitative analysis on trace samples.

[0036] Therefore, current research on terahertz metasurface trace detection mainly focuses on two strategies: one is broadband molecular fingerprint sensing based on multiplexing broadband enhancement. Due to the non-uniform enhancement between multiplexed signals, accurate quantitative analysis is difficult to achieve, so it is mainly used for qualitative analysis; the other is refractive index sensing based on narrowband enhanced resonance. Limited by the narrowband resonance characteristics, it cannot effectively identify broadband molecular fingerprint features, so it is mainly used for quantitative analysis. Both strategies have limitations in qualitative and quantitative analysis, making it difficult to simultaneously detect trace molecules qualitatively and quantitatively, which greatly restricts the practical application of terahertz metasurface sensing technology in the field of trace detection.

[0037] To address the aforementioned problems, the inventors, through extensive research, have creatively proposed a terahertz molecular fingerprint sensor and electronic device based on an overcoupled metasurface, as described in this application. The technical solution of this application is explained and described in detail below.

[0038] This application discloses a terahertz molecular fingerprint sensor based on an overcoupled metasurface, comprising: an array of fingerprint detection units of the same structure arranged periodically; and a reference... Figure 1 The diagram shows a modular design for each fingerprint detection unit, which includes a substrate layer, a first metal layer, and a raised structure.

[0039] The first metal layer is disposed above the substrate layer, and both have equal cross-sectional areas. The protruding structure is disposed above the first metal layer, and its cross-sectional area is smaller than that of the first metal layer. When the terahertz molecular fingerprint sensor detects the sample to be tested, the sample to be tested is coated on the target position of the first metal layer and the upper surface of the protruding structure. The target position refers to the position on the upper surface of the first metal layer that is not occupied by the protruding structure. After the sample to be tested is coated, the terahertz wave is set to be perpendicularly incident on the coupling metasurface. By adjusting the volume of the protruding structure, the coupling state between the terahertz wave and the metasurface can be changed, thereby enabling qualitative and quantitative detection of the sample to be tested.

[0040] The terahertz molecular fingerprint sensor proposed in this application, based on the traditional MIM resonator structure, alters the coupling state between the terahertz wave and the metasurface by adjusting the volume of the protruding structure. Specifically, it excites an overcoupling effect by precisely controlling the ratio of radiation loss to absorption loss in the resonant system. The overcoupling effect refers to a situation where the radiation loss of the resonant cavity is much greater than the absorption loss. In this case, the system response exhibits a wide-bandwidth, near-flat-top absorption characteristic, significantly enhancing the near-field intensity at non-resonant frequencies and achieving broadband absorption enhancement. Under vertically incident terahertz wave excitation, based on the broadband-enhanced resonant absorption peak, simultaneous qualitative and quantitative detection of trace samples is achieved. The entire terahertz molecular fingerprint sensor requires only a single resonant signal to achieve broadband enhanced sensing. This not only facilitates simultaneous qualitative and quantitative detection of trace samples but also simplifies optical path configuration and structural complexity, significantly improving detection efficiency.

[0041] In one embodiment of this application, the protrusion structure preferably includes: a dielectric layer and a second metal layer. (See also...) Figure 2 The diagram shown is a three-dimensional structural schematic of a fingerprint detection unit after coating the sample to be tested. (Refer to...) Figure 3 The diagram shows a top view of a preferred fingerprint detection unit after coating the sample to be tested, and a reference. Figure 4 The diagram shows a side view of a preferred fingerprint detection unit after coating the sample to be tested.

[0042] A preferred fingerprint detection unit after coating the sample to be tested includes: a sample layer 1, a second metal layer 2, a dielectric layer 3, a sample layer 4, a first metal layer 5, and a substrate layer 6. The dielectric layer 3 is disposed above the first metal layer 5, and the second metal layer 2 is disposed above the dielectric layer 2; the dielectric layer 3 and the second metal layer 2 form a raised structure. When the terahertz molecular fingerprint sensor detects the sample to be tested, the sample is coated on the upper surface of the second metal layer 5, that is, sample layer 1 is located above the second metal layer 5, and sample layer 2 is located above the first metal layer 5. It is understood that the space occupied by the dielectric layer 3 on the upper surface of the first metal layer 5 cannot be coated with the sample to be tested.

[0043] In one embodiment of this application, the coupling state between the terahertz wave and the metasurface is preferably changed by adjusting the volume of the protrusion structure. When adjusting the volume of the protrusion structure, the thickness of the dielectric layer 3 is preferentially changed, while the length and width of the dielectric layer 3 and the dimensions of the second metal layer 2 remain unchanged. For example: Figure 3 As shown, L Indicates the length of dielectric layer 3, W Indicates the width of dielectric layer 3, such as Figure 4 As shown, t 1 indicates the thickness of dielectric layer 3. When it is necessary to change the volume of the protrusion structure, the thickness of dielectric layer 3 should be changed first. t 1. Maintain the length of dielectric layer 3L ,width W . Figure 4 middle t s Indicates the thickness of the sample layer, t au Indicates the thickness of the metal layer. t 2 indicates the thickness of the substrate layer.

[0044] If the thickness of dielectric layer 3 is changed t 1. If the requirement to change the coupling state between the terahertz wave and the metasurface cannot be met, then the lengths of the dielectric layer 3 and the second metal layer 2 can be further changed. L ,width W Maintain the thickness of the second metal layer 2 t au The length remains unchanged. Since the second metal layer 2 is disposed above the dielectric layer 3, and its cross-sectional area is the same as that of the dielectric layer 3, the length of the dielectric layer 3 can be changed. L ,width W This is equivalent to changing the length of the second metal layer 2. L ,width W .

[0045] By adjusting the volume of the protruding structure, the coupling state between the terahertz wave and the metasurface is changed, so that the coupling state between the two changes from undercoupling to critical coupling and then to overcoupling, thereby stimulating the overcoupling effect and thus enabling qualitative and quantitative detection of the sample to be tested.

[0046] In one embodiment of this application, the shape of the protrusion structure can be arbitrary, but a cross shape is preferred. For example... Figure 2 , 3 The shape shown in Figure 4 is a cross shape. Of course, it can also be any other shape, as long as its cross-sectional area is smaller than the cross-sectional area of ​​the first metal layer 5. It is understandable that the shape of the substrate layer 6 can also be arbitrary. Figure 2 , 3 Section 4 uses a cuboid as an example only.

[0047] In one embodiment of this application, the materials of the substrate layer, the first metal layer, the second metal layer, and the dielectric layer can be various, with a preferred choice being: the substrate layer is made of silicon dioxide; the first metal layer and the second metal layer are made of gold; and the dielectric layer is made of resin.

[0048] In one embodiment of this application, the conductivity of gold (Au) in the terahertz band is 5.96 × 10⁻⁶. 7 S / m, the refractive index range of silicon dioxide (SiO2) is 1.92-1.97, and the refractive index range of resin (Resin) is 1.659-1.665.

[0049] Overcoupled metasurface structures are defined by the following parameters: substrate periodicity P ( Figure 3 (as shown in the figure), substrate thickness t 2. Metal layer thickness t au Dielectric layer thickness t 1. Dielectric layer length L Dielectric layer width W Sample layer thickness t s The specific values ​​of the substrate period, the thickness, length, and width of the dielectric layer, and the coating thickness of the sample can be determined by the frequency range of the fingerprint spectrum of the sample.

[0050] The preferred options are: a substrate period ranging from 75 μm to 110 μm; a substrate thickness of 200 μm; and a substrate period of... P The resonant frequency is determined by the following parameters: the thickness of the first and second metal layers is the same, both 200 nm; the thickness of the dielectric layer ranges from 1 μm to 40 μm, the length ranges from 70 μm to 100 μm, and the width ranges from 1 μm to 5 μm; the thickness of the sample coating ranges from 1 μm to 5 μm. It should be noted that the thickness of the sample layer may be greater than, less than, or equal to the thickness of the dielectric layer, depending on the frequency range of the fingerprint spectrum of the sample. Figure 4 For the sake of simplicity, the illustration shows that the thickness of sample layer 4 is less than the thickness of dielectric layer 3, but this does not mean that the thickness of the sample layer can only be less than the thickness of the dielectric layer.

[0051] The terahertz molecular fingerprint sensor based on an overcoupled enhanced terahertz metasurface proposed in this application achieves this by setting the terahertz wave to be perpendicularly incident on the overcoupled metasurface and adjusting the volume of the protruding structure to change the coupling state between the terahertz wave and the metasurface. This allows for precise control of the ratio of radiation loss to absorption loss, generating overcoupled resonance. Compared to traditional narrowband high-resolution sensors... Q Resonance, without the need for multiplexing or additional control mechanisms, enables broadband fingerprint signal enhancement based on a single resonance. The entire terahertz molecular fingerprint sensor, based on a single metasurface device, achieves simultaneous qualitative and quantitative analysis of trace substances, solving the problem of existing sensing mechanisms requiring separate detection by different sensors. Therefore, the terahertz molecular fingerprint sensor of this application has a wide range of applications and excellent scalability. It can be applied to the identification and detection of various small molecules such as explosives and sugars, involving multiple scenarios including national defense security and biomedicine, with a broad application market and strong application scenario expansion.

[0052] To better verify the effectiveness of the terahertz molecular fingerprint sensor proposed in this application, the sample to be tested was used as... ε -HNIW ( ε For example, actual tests were conducted using hexanitrohexaazaisowulzane and sucralose.

[0053] First, the sample to be tested is not coated. The parameters are: substrate period... P The substrate thickness is 60 μm. t 2 is 200μm, metal layer thickness t au The dielectric layer length is 200 nm. L The dielectric layer width is 55 μm. W The sample layer thickness is 5 μm. t s We will test with a value of 0 as an example.

[0054] When a terahertz wave is incident perpendicularly through a coupled metasurface, the thickness of the dielectric layer can be changed. t 1. Modify the coupling state between terahertz waves and metasurfaces to achieve a transition from undercoupling to critical coupling and then to overcoupling. See also Figure 5 The coupling state curve shown has the horizontal axis representing frequency (THz) and the vertical axis representing absorption.

[0055] when t When 1 = 2 μm, the metasurface is in an undercoupled state, the resonance is sharp, and the absorption rate does not reach 1; when t When 1 = 3 μm, the metasurface is in a critical coupling state, exhibiting a sharp resonance and an absorption rate of 1; when t When 1 = 10 μm, the metasurface is in an overcoupled state, the resonance becomes approximately flat-topped, and the absorption in the broadband range outside the resonance frequency is slightly increased compared to the previous two. This experiment, along with subsequent changes in the dielectric layer length, demonstrates this. L ,width W Tests show that by adjusting the thickness of the dielectric layer... t 1. Length L ,width W Both can effectively control the resonant frequency and coupling state. The period P determines the resonant frequency, and the parameter selection has good versatility and adjustability.

[0056] Reference Figure 6 The resonant peak frequencies (frequency) shown under different coupling states f =1.938THz, frequency f =1.976THz, frequency f =1.930THz) and frequency f =1.600THz and fThis is a schematic diagram of the electric field distribution at 2.400 THz. To better and more intuitively display the electric field distribution, a colorless view is insufficient to accurately represent it. Therefore... Figure 6 Presented in color. The electric field distribution diagram shows that the electric field intensity at different frequencies in the undercoupled state is weaker compared to the critically coupled and overcoupled states; while in the critically coupled state, only the resonant frequency is present. f The electric field strength is relatively strong at 1.976 THz, while the electric field strength at the other two locations far from the resonance peak frequency is very weak; in contrast, under overcoupling conditions, except for the resonance peak frequency... f Beyond 1.930THz, f =1.600THz and f The electric field intensity at 2.400 THz also exhibits a relatively strong electric field intensity, showing an electric field enhancement effect at different frequencies within a wide bandwidth.

[0057] This also verifies that overcoupled metasurfaces can regulate the ratio of radiation loss to absorption loss by changing structural parameters, thereby stimulating the overcoupling effect and enabling strong near-field enhancement at different frequency positions across a wide bandwidth. Therefore, in practical testing, when a sample is placed above the metasurface structure, it can significantly enhance the absorption of terahertz waves across a wide frequency range, thus achieving broadband molecular fingerprint-specific identification and detection of trace samples. Furthermore, this structure does not rely on multiplexing technology, avoiding complex fabrication processes and uneven enhancement performance between different structures. It also simplifies testing conditions, allowing for simultaneous qualitative and quantitative detection of trace molecules using a single device.

[0058] To further verify the effectiveness of qualitative and quantitative detection of the test sample, the above-mentioned overcoupled metasurface terahertz molecular fingerprint sensor was coated with the test sample. ε -HNIW and sucralose, from ε - The frequency range of the fingerprint spectra of HNIW and sucralose determines each parameter.

[0059] When the sample to be tested is ε During -HNIW, the period P The dielectric layer thickness is 75 μm. t 1 is 25μm, dielectric layer length L 70μm, width W 5μm, substrate thickness t 2 is 200μm, metal layer thickness t au The sample layer thickness is 200 nm. t s It is 1μm.

[0060] Reference Figure 7The sample to be tested shown is ε A schematic diagram of the performance curve of the -HNIW terahertz molecular fingerprint sensor, showing the unloaded signal (metasurface unloaded) when no sample is loaded. ε The absorption spectrum at -HNIW (within the HNIW range) exhibits a near-flat-topped single-peak signal. After loading the sample, the terahertz wave is incident perpendicularly on the overcoupled metasurface, changing the coupling state between the terahertz wave and the metasurface to enter the overcoupled state. The loaded signal (with a 1μm thick layer of material loaded on the metasurface) is obtained. ε The absorption spectrum at -HNIW showed significant changes compared to the unloaded signal, exhibiting markedly enhanced absorption peaks near 1.312 THz and 1.424 THz, respectively. Subtracting the unloaded signal from the loaded signal yields the enhanced sample signal. Figure 7 In the second curve from top to bottom, the black solid line represents the sample signal obtained by subtracting the loaded signal from the unloaded signal, and the signal composed of dots represents the pure sample signal, i.e., the signal at a thickness of 1 μm. ε -HNIW's own absorption signal).

[0061] Due to the principle of broadband enhancement caused by overcoupling effect, ε The fingerprint peak characteristics of -HNIW at 1.312 THz and 1.424 THz were enhanced, and the enhanced sample signal was similar to... ε -HNIW's own optical parameters k Value curve ( Figure 7 The topmost curve, that is ε -HNIW fingerprint features, with the corresponding ordinate representing optical parameters. k It exhibits consistency, reproducing the molecular fingerprint characteristics of the sample under test, and achieving broadband molecular fingerprint detection. Next, it... ε The absorption enhancement of the -HNIW sample in the broadband terahertz frequency range was evaluated, compared with that of a 1 μm thick sample. ε The reference absorption of the HNIW pure sample revealed that the overcoupled metasurface produced a broadband absorption enhancement on the sample, with the maximum peak enhancement reaching 19.9 times.

[0062] When the sample to be tested is sucralose, the cycle P The dielectric layer thickness is 100 μm. t 1 is 25μm, dielectric layer length L 90μm, width W The sample layer thickness is 5 μm. t s The substrate thickness is 5 μm. t 2 is 200μm, metal layer thickness t au It is 200nm.

[0063] Reference Figure 8The diagram shows the performance curve of the terahertz molecular fingerprint sensor with sucralose as the test sample. When no sample is loaded, the unloaded signal (absorption spectrum of the metasurface without sucralose) exhibits a slowly rising single-peak signal. After loading the sample, the terahertz wave is incident perpendicularly on the overcoupled metasurface, changing the coupling state between the terahertz wave and the metasurface to an overcoupled state. The loaded signal (absorption spectrum of the metasurface with a 1 μm thick sucralose layer) shows a significant change compared to the unloaded signal, exhibiting enhanced absorption peaks near 0.950 THz and 1.158 THz, respectively. Subtracting the unloaded signal from the loaded signal yields the enhanced sample signal. Figure 8 In the second curve from top to bottom, the solid black line represents the sample signal obtained by subtracting the loaded signal from the unloaded signal, and the signal composed of dots represents the pure sample signal, which is the absorption signal of sucralose itself at a thickness of 1 μm.

[0064] Due to the broadband enhancement principle of overcoupling, the fingerprint peak characteristics of sucralose at 0.950 THz and 1.158 THz are enhanced. The enhanced sample signal is consistent with the optical parameters of sucralose itself. k Value curve ( Figure 8 The topmost curve, representing the fingerprint characteristics of sucralose, has its vertical axis corresponding to optical parameters. k The method exhibits consistency, reproducing the molecular fingerprint characteristics of the sample and achieving broadband molecular fingerprint detection. Next, the absorption enhancement of the sucralose sample in the broadband terahertz frequency range was evaluated. By comparing the absorption with the reference absorption of a 1 μm thick pure sucralose sample, it was found that the overcoupled metasurface produced broadband absorption enhancement in the sample, with a maximum peak enhancement reaching 26.8 times.

[0065] The above actual tests show that the overcoupled metasurface terahertz molecular fingerprint sensor achieves overcoupled resonance by adjusting structural parameters, realizing near-field enhancement in a wide range and improving the absorption signal of trace samples. It only requires a single device and a single incident signal for single detection, which can realize broadband fingerprint detection of trace samples. The whole process only requires loading the sample onto the sensor, without the need for additional sample processing. The detection method is convenient and has little impact on the sample.

[0066] Based on the above-mentioned terahertz molecular fingerprint sensor, this application embodiment also provides an electronic device, the electronic device comprising: a terahertz molecular fingerprint sensor based on an overcoupled metasurface as described in any of the preceding claims.

[0067] In summary, the terahertz molecular fingerprint sensor based on an overcoupled metasurface proposed in this application includes: a plurality of fingerprint detection units periodically arranged; each fingerprint detection unit includes: a substrate layer, a first metal layer, and a protrusion structure. The first metal layer is disposed above the substrate layer, and the two have equal cross-sectional areas; the protrusion structure is disposed above the first metal layer, and its cross-sectional area is smaller than that of the first metal layer.

[0068] In this process, when a terahertz molecular fingerprint sensor detects a sample, the sample is coated onto a target location on the first metal layer and the upper surface of the raised structure. The target location refers to a position on the upper surface of the first metal layer that is not occupied by the raised structure; that is, the area where the raised structure connects to the first metal layer cannot be coated with the sample. By setting the terahertz wave to be perpendicularly incident on the overcoupled metasurface and adjusting the volume of the raised structure, the coupling state between the terahertz wave and the metasurface can be changed, thus enabling qualitative and quantitative detection of the sample.

[0069] This application creatively proposes a novel overcoupled metasurface terahertz molecular fingerprint sensor based on the traditional metal-insulator-metal (MIM) resonator. By finely controlling the ratio of radiation loss to absorption loss in the resonant system to excite the overcoupling effect, a broadband enhanced resonant absorption peak can be formed with only a vertically incident terahertz wave excitation, thereby detecting broadband molecular fingerprint spectra under a single resonant signal.

[0070] A terahertz molecular fingerprint sensor, formed by multiple periodically arranged fingerprint detection units, features a top metal array, a dielectric modulation layer, a bottom continuous metal layer, and a sample capping layer, creating a stable and controllable radiation-dominated resonant cavity system that effectively supports the generation of overcoupled states. This structural layout, as the fundamental configuration for realizing overcoupled states, represents a key innovation that distinguishes it from traditional technologies in its combination and parameter control mechanisms.

[0071] Overcoupling resonance is generated by finely controlling the ratio of radiation loss to absorption loss, resulting in low... Q The high-value, high-intensity, and broadband response of the quasi-flat-top resonant state significantly enhances the electromagnetic field enhancement effect of the sample at multiple absorption frequencies, i.e., it utilizes an overcoupling mechanism to achieve broadband enhanced response. Compared to traditional narrowband high-intensity resonant states, this significantly improves the electromagnetic field enhancement effect of the sample at multiple absorption frequencies. Q Resonance, without the need for multiplexing or additional control mechanisms, can achieve broadband fingerprint signal enhancement based on a single resonance. It also establishes the control relationship between metal layer thickness, dielectric layer length, periodic parameters, and the resonance state, and provides device design rules for stably generating overcoupled states, adaptable to broad-spectrum sensing needs across multiple frequency bands and different dielectric types.

[0072] The entire terahertz molecular fingerprint sensor, based on a single metasurface device, enables simultaneous qualitative and quantitative analysis of trace substances. It is the first to achieve collaborative operation of both qualitative and quantitative functions within a single structure / single channel. Unlike traditional multi-pixel or angle-multiplexing schemes, it covers the broadband absorption of target molecules through a single resonant state coupling platform, while also possessing frequency shift response capabilities, enabling simultaneous qualitative identification and quantitative detection of trace molecules. This solves the problem of existing sensing mechanisms requiring separate detection by different sensors.

[0073] The terahertz molecular fingerprint sensor of this application requires only a single device and performs a single detection using a single incident signal to achieve broadband fingerprint detection of trace samples. The entire process only requires loading the sample onto the terahertz molecular fingerprint sensor, without the need for additional sample processing. The detection method is convenient and has minimal impact on the sample. It enables simultaneous qualitative and quantitative detection of various trace samples, overcoming the performance incompatibility between existing broadband and narrowband solutions. It achieves "dual detection with one device" for trace samples, and has a wide range of applications and excellent scalability. It can be applied to the identification and detection of various small molecules such as explosives and sugars, involving multiple scenarios such as national defense security and biomedicine. It has a broad application market, strong application scenario scalability, and high practicality.

[0074] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0075] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0076] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims. All of these forms are within the protection scope of this application.

Claims

1. A terahertz molecular fingerprint sensor based on an overcoupled metasurface, characterized in that, include: A fingerprint detection unit array with the same structure deployed periodically; Each of the fingerprint detection units includes: a substrate layer, a first metal layer, and a raised structure; The first metal layer is disposed above the substrate layer, and the two have equal cross-sectional areas; The protruding structure is arranged above the first metal layer, and its cross-sectional area is smaller than that of the first metal layer. When the terahertz molecular fingerprint sensor detects the sample to be tested, the sample to be tested is coated on the target position of the first metal layer and the upper surface of the protrusion structure. The target position refers to the position on the upper surface of the first metal layer that is not occupied by the protrusion structure. By setting a terahertz wave to be incident perpendicularly on the overcoupled metasurface and adjusting the volume of the protrusion structure to change the coupling state between the terahertz wave and the metasurface, the sample to be tested can be qualitatively and quantitatively detected.

2. The terahertz molecular fingerprint sensor according to claim 1, characterized in that, The protrusion structure includes: a dielectric layer and a second metal layer; The dielectric layer is disposed above the first metal layer, and the second metal layer is disposed above the dielectric layer; When the terahertz molecular fingerprint sensor detects the sample to be tested, the sample to be tested is coated on the upper surface of the second metal layer.

3. The terahertz molecular fingerprint sensor according to claim 2, characterized in that, When adjusting the volume of the protrusion structure, the thickness of the dielectric layer is changed first, while the length and width of the dielectric layer and the size of the second metal layer remain unchanged; If changing the thickness of the dielectric layer cannot achieve the desired change in the coupling state, then the length and width of the dielectric layer and the second metal layer are further changed while keeping the thickness of the second metal layer constant.

4. The terahertz molecular fingerprint sensor according to claim 1, characterized in that, The shape of the protrusion can be arbitrary, but a cross shape is preferred.

5. The terahertz molecular fingerprint sensor according to claim 1, characterized in that, By adjusting the volume of the protruding structure, the coupling state between the terahertz wave and the metasurface is changed, so that the coupling state between the two changes from undercoupling to critical coupling and then to overcoupling, thereby stimulating the overcoupling effect and performing qualitative and quantitative detection on the sample to be tested.

6. The terahertz molecular fingerprint sensor according to claim 1, characterized in that, The substrate layer is made of silicon dioxide; The material of the first metal layer includes: gold.

7. The terahertz molecular fingerprint sensor according to claim 2, characterized in that, The material of the second metal layer includes: gold; The material of the dielectric layer includes: resin.

8. The terahertz molecular fingerprint sensor according to claim 2, characterized in that, The period of the substrate layer ranges from 75μm to 110μm; the thickness of the substrate layer is 200μm; the period of the substrate layer determines the resonant frequency. The first metal layer and the second metal layer have the same thickness, both being 200 nm. The thickness of the dielectric layer ranges from 1 μm to 40 μm, the length of the dielectric layer ranges from 70 μm to 100 μm, and the width of the dielectric layer ranges from 1 μm to 5 μm. The thickness of the coating on the sample to be tested ranges from 1 μm to 5 μm.

9. The terahertz molecular fingerprint sensor according to claim 8, characterized in that, The specific values ​​of the period of the substrate layer, the specific values ​​of the thickness, length, and width of the dielectric layer, and the specific value of the coating thickness of the sample under test are determined by the frequency range of the fingerprint spectrum of the sample under test.

10. An electronic device, characterized in that, The electronic device includes: a terahertz molecular fingerprint sensor based on an overcoupled metasurface as described in any one of claims 1-9.

Images