Disc double-notch-shaped multifunctional metasurface sensor, application and preparation method

Abstract

The invention relates to the technical field of metasurface sensing, in particular to a disc double-notch-shaped multifunctional metasurface sensor and a preparation method thereof.The sensor comprises a quartz substrate and double-notch silicon nanometer discs arranged on the quartz substrate in a periodic array; the double-notch silicon nanodisk comprises a first notch and a second notch, the opening directions of the first notch and the second notch are opposite, and the included angle between the opening directions of the first notch and the second notch and the side length direction of the quartz substrate is 45 degrees; and the first gap and the second gap are different in geometric dimension and / or position, so that the double-gap silicon nano-disk forms an asymmetric structure for exciting Fano resonance of the magnetic dipole to realize a sensing function. The method has the advantages that the limitation of traditional single-parameter detection is broken through, multi-parameter synchronous measurement and multi-phase detection (gas and liquid) are realized, the practical application scene is greatly expanded, and the method can be widely applied to the fields of environmental monitoring, biomedical detection, optical switch control and the like.

Description

Technical Field

[0001] This invention relates to the field of metasurface sensing technology, and in particular to a disk-shaped double-notch multifunctional metasurface sensor, its applications, and its fabrication method. Background Technology

[0002] Artificial two-dimensional metamaterials (metasurfaces) have shown significant application potential in the field of optical sensing due to their unique electromagnetic manipulation capabilities. With breakthroughs in nanofabrication technology, various metasurface sensors have emerged and are widely used in environmental monitoring, biomedical detection, and other fields, particularly in refractive index sensors. Compared to traditional optical sensors, these devices possess compact subwavelength-scale structures and excellent optical field localization capabilities, offering significant advantages in on-chip integrated sensing systems and high-sensitivity detection.

[0003] The core of metasurface sensors lies in their carefully designed subwavelength structures, which generate strong near-field enhancement effects and excite characteristic optical resonance responses (including characteristic transmission valleys or absorption peaks). Among these, the magnetic dipole Fano resonance has attracted considerable attention due to its unique asymmetric spectral characteristics; this physical phenomenon originates from the quantum mechanical interference between discrete and continuous energy states. When the analyte undergoes near-field coupling with the metasurface nanostructure, it causes significant changes in the resonance characteristics, manifested as a shift in the resonance wavelength or a change in the peak amplitude. These measurable optical responses provide reliable evidence for material detection.

[0004] In practical applications, refractive index sensing has become a primary application area because optical sensing signals are usually closely related to the refractive index of the medium (e.g., the concentration of a solution has a deterministic relationship with its refractive index). All-dielectric metasurface sensing platforms, with their low optical loss characteristics, can achieve extremely high quality factors (Q factors) and performance indicators (FOM). However, current metasurface sensors are functionally limited, often restricted to single-parameter detection and lacking temperature compensation, and also suffer from insufficient compatibility with gaseous substances, thus failing to meet the diverse detection needs of complex environments. Summary of the Invention

[0005] Based on this, the present invention proposes a disk-shaped double-notch multifunctional metasurface sensor, its applications, and its fabrication method. By using a periodically arrayed double-notch silicon nanodiscs on a quartz substrate, the ohmic loss problem of traditional metallic metasurface sensors is overcome. While achieving a high quality factor, the practical application scenarios are greatly expanded, and it can be widely used in environmental monitoring, biomedical detection, and optical switch control, among other fields.

[0006] To achieve the above objectives, the technical solution of this invention is as follows: a disc-shaped multifunctional metasurface sensor, comprising: a quartz substrate, and a double-notched silicon nanodisc disposed on the quartz substrate in a periodic arrangement; the double-notched silicon nanodisc includes a first notch and a second notch, the openings of the first notch and the second notch are oriented in opposite directions, and both openings are oriented at a 45° angle to the side length direction of the quartz substrate; the first notch and the second notch have different geometric dimensions and / or positions, so that the double-notched silicon nanodisc forms an asymmetric structure for exciting Fano resonance based on magnetic dipoles to achieve sensing function.

[0007] Furthermore, the widths of the first notch and the second notch are not equal; and / or, the distances from the first notch and the second notch to the center of the double-notched silicon nanodisk are not equal.

[0008] A disk-shaped, double-notch, multifunctional metasurface sensor as described above is used to realize at least one of the following functions: gas-liquid compatible sensing, temperature sensing, wideband sensing, and polarization-type optical switching.

[0009] A gas volume fraction detection sensor includes a disk-shaped double-notch multifunctional metasurface sensor as described above, wherein a specific gas-sensitive thin film is disposed on the surface of the disk-shaped double-notch multifunctional metasurface sensor.

[0010] Furthermore, the specific gas-sensitive film is a cryptoalkyl A molecule methane gas-sensitive film or a palladium-tungsten oxide hydrogen gas-sensitive film.

[0011] A method for fabricating a disk-shaped double-notch multifunctional metasurface sensor, comprising the following steps: S1: Clean the quartz substrate; S2: Amorphous silicon film is deposited on a cleaned quartz substrate using plasma-enhanced chemical vapor deposition (PECVD). S3: A tackifier, a positive photoresist, and a conductive adhesive are sequentially coated onto a quartz substrate on which an amorphous silicon film has been deposited. S4: Define nanostructure patterns using electron beam lithography, and then develop and fix them; S5: The pattern is transferred to the silicon layer by inductively coupled plasma-reactive ion etching technology to form a periodic array of double-notch silicon nanodisks. S6: Remove residual photoresist and byproducts to obtain a disk-shaped double-notch multifunctional metasurface sensor.

[0012] A method for preparing the above-mentioned gas volume fraction detection sensor includes the following steps: A specific gas-sensitive thin film is coated onto the upper surface of a disc-shaped, double-notch, multifunctional metasurface sensor using a capillary dip-coating process.

[0013] The present invention achieves the following beneficial effects: the metasurface sensor proposed in this invention has advantages such as simple operation, low experimental requirements, and low fabrication cost. Its sensor structure can be fabricated with only a single etching process, greatly simplifying the process flow. Compared with traditional metal metasurface sensors, this scheme uses all-dielectric materials, significantly reducing optical loss and exhibiting higher sensitivity and a wider detection range in refractive index detection.

[0014] In terms of functional expansion, this invention breaks through the limitations of traditional single-parameter detection, realizing simultaneous measurement of multiple parameters and detection of multiple phases (gas and liquid), greatly expanding practical application scenarios and enabling its widespread application in fields such as environmental monitoring, biomedical detection, and optical switch control. Furthermore, this device possesses direct detection capabilities, eliminating the need for pretreatment of original samples (such as serum, buffer solutions, microbial cultures, etc.) such as dilution, centrifugation, and labeling, significantly improving detection efficiency and practicality. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a disk-shaped double-notch multifunctional metasurface sensor provided according to an embodiment of the present invention; Figure 2 This is a comparison of the transmission spectra of the symmetrical and asymmetrical structures of the double-notched silicon nanodiscs according to embodiments of the present invention; Figure 3 This is a schematic diagram of the electromagnetic field structure of the symmetrical and asymmetrical structures of the double-notched silicon nanodisk according to an embodiment of the present invention; Figure 4 This is a comparison diagram of the electric and magnetic field distributions of the double-notched silicon nanodisk symmetric structure provided in the embodiments of the present invention; Figure 5 This is a comparison diagram of the electric and magnetic field distributions of the asymmetric structure of the double-notched silicon nanodisk provided in the embodiments of the present invention; Figure 6 This is a graph showing the effect of changing the geometric parameters of a disk-shaped double-notch multifunctional metasurface sensor on the transmission spectrum, according to an embodiment of the present invention. Figure 7 This is a transmission spectrum and sensitivity fitting diagram of a disc-shaped double-notch multifunctional metasurface sensor for liquid sensing provided according to an embodiment of the present invention. Figure 8 This is a transmission spectrum and sensitivity fitting diagram of a disc-shaped double-notch multifunctional metasurface sensor for temperature sensing provided according to an embodiment of the present invention. Figure 9 This is a transmittance diagram of a disk-shaped double-notch multifunctional metasurface sensor provided according to an embodiment of the present invention under different polarization angles; Figure 10 This is a diagram illustrating the sensing effect of a disc-shaped double-notch multifunctional metasurface sensor for methane volume fraction according to an embodiment of the present invention. Figure 11 This is a diagram illustrating the sensing effect of a disc-shaped double-notch multifunctional metasurface sensor for hydrogen gas integrals, provided according to an embodiment of the present invention. Figure 12 This is a flowchart of a method for fabricating a disk-shaped, double-notch, multifunctional metasurface sensor according to an embodiment of the present invention.

[0016] The reference numerals in the attached figures include: 1, quartz substrate; 2, double-notched silicon nanodisk; 21, first notch; 22, second notch. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention 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 merely illustrative of the invention and do not constitute a limitation thereof.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The invention will now be described in detail with reference to specific embodiments.

[0022] like Figures 1 to 12 As shown in the figure, an embodiment of the present invention provides a disk-shaped multifunctional metasurface sensor, comprising: a quartz substrate 1, and an array of periodically arranged array units disposed on the quartz substrate, each array unit having a double-notched silicon nanodisk 2. The double-notched silicon nanodisk 2 includes a first notch 21 and a second notch 22, the first notch 21 and the second notch 22 facing opposite directions, and both openings forming a 45° angle with the side length direction of the quartz substrate 1. The first notch 21 and the second notch 22 have different geometric dimensions and / or positions, so that the double-notched silicon nanodisk 2 forms an asymmetric structure for exciting the Fano resonance of the magnetic dipole to achieve the sensing function.

[0023] An array cell refers to a structure on a quartz substrate, in which countless array cells are arranged periodically in a checkerboard pattern on a two-dimensional plane. Each array cell contains a double-notched silicon nanodisk. The two side lengths Px and Py of the array cell in the X and Y axes define the basic lattice of this arrangement, serving as a bridge between microscopic nanostructures and macroscopic optical functions.

[0024] The width of the first notch 21 is not equal to the width of the second notch 22; and / or, the distances from the first notch 21 and the second notch 22 to the center of the double-notch silicon nanodisk are not equal.

[0025] The disc-shaped double-notch multifunctional metasurface sensor of this invention is constructed from silicon with a refractive index of 3.45 and silicon dioxide (quartz) with a refractive index of 1.45. The metasurface sensor operates in an aqueous environment with a refractive index of 1.33. It is then excited by a laser beam that is vertically irradiated from top to bottom with a polarization direction of Y, and its optical response (transmission spectrum) is observed.

[0026] In this embodiment, the specific parameters for fabricating the disk-shaped double-notch multifunctional metasurface sensor are as follows: The two sides of the array unit have lengths Px=Py=950nm and a height H of 3000nm.

[0027] The radius of the double-notched silicon nanodisk 2 is R=300nm and the height h is 200nm.

[0028] The width m1 of the first notch 21 is 220nm, and the distance L1 from it to the center of the disk is 140nm.

[0029] The width m2 of the second gap 22 is 200nm, and the distance L2 from the center of the disk is 150nm.

[0030] This invention utilizes the asymmetry of the double-notched silicon nanodisk 2 to excite the Fano resonance of a magnetic dipole. Specifically, the ratio of the areas of the first notch 21 and the second notch 22 is defined as the asymmetry factor ∆. The rotational symmetry of the double-notched silicon nanodisk 2 is broken by reducing the area of ​​the second notch 22. Under the specific parameters set in this embodiment, the calculated asymmetry factor... .

[0031] like Figure 2 As shown in (a), when the two notches of the double-notched silicon nanodisk 2 are completely symmetrical, no obvious Fano resonance of the magnetic dipole is observed in the transmission spectrum curve of the metasurface sensor.

[0032] like Figure 2 As shown in (b), when the two notches of the double-notched silicon nanodisk 2 are asymmetrical, based on the continuous-domain bound state theory, this asymmetry causes energy leakage within the metasurface sensor structure, thereby transforming the BIC state (continuous-domain bound state) with an infinite quality factor into a quasi-BIC state (quasi-continuous-domain bound state). The resulting Fano resonance peak is located at a wavelength of 1617 nm. This resonance mode, dominated by magnetic dipole resonance, constitutes the physical basis for realizing high-sensitivity sensing.

[0033] like Figure 3 As shown, by calculating the electric field in the XY plane and the magnetic field strength and vector direction in the ZX plane of the metasurface sensor at the resonance wavelength λ=1617nm, the resonance mechanism generated by the Fano resonance of the magnetic dipole can be analyzed. Figure 3 The black arrows in the image indicate the direction of the electromagnetic field. At this time, symmetrical structures exhibit an electric dipole moment (ED) phenomenon. At this time, the introduction of asymmetry disrupts the original resonance mechanism, and the magnetic dipole (MD) becomes the main contributing pole. This resonance mode excited by the strong local field of the MD is one of the reasons why this metasurface sensor has an ultra-high quality factor response and high sensitivity.

[0034] like Figure 3 (a1) in the diagram is a schematic diagram of the electromagnetic field of the double-notched silicon nanodisk 2; as shown in Figure 2. Figure 3(a2) is a schematic diagram of the magnetic dipole of the double-notched silicon nanodisk 2; like Figure 4 (a1) in the text is a symmetrical structure. The electric field distribution in the XY plane is shown. This distribution was obtained at the center upper surface Z=100nm of the symmetrical double-notched silicon nanodisk 2, and its symmetry mode is consistent with the characteristics of electric dipole resonance.

[0035] like Figure 4 (a2) is a symmetrical structure. The magnetic field intensity distribution on the ZX plane. Figure 4 (a2) shows the magnetic field strength (usually represented by color depth) through the central vertical section of the double-notched silicon nanodisk 2 in the symmetrical case, and the magnetic field distribution pattern matches the electric dipole resonance.

[0036] like Figure 5 (a1) in the text is an asymmetric structure. The electric field distribution in the XY plane. This distribution was obtained at the center upper surface Z=100nm of the asymmetric double-notched silicon nanodisk 2. The electric field distribution is significantly changed due to the breaking of symmetry, no longer showing a regular symmetric pattern, but showing a clear toroidal loop direction.

[0037] like Figure 5 (a2) is an asymmetric structure. The magnetic field intensity distribution in the ZX plane. (e.g.) Figure 5 Figure (a2) shows the magnetic field distribution on a vertical cross-section passing through the center of the double-notched silicon nanodisk 2 in the asymmetric case. It can be observed that the magnetic field strength is highly localized within the double-notched silicon nanodisk 2. The black arrows in the figure clearly indicate the direction of the magnetic field vector. The observation that the magnetic field vector direction is from bottom to top indicates that magnetic dipoles are excited.

[0038] The resonant peak position (wavelength and transmittance) of metasurface sensors is significantly influenced by their key geometric parameters. For example... Figure 6 As shown, when the radius R and height h of the double-notched silicon nanodisk 2, or the side lengths Px and Py of the array unit 1 in the X and Y axes, increase, the resonance peaks in the transmission spectrum all undergo varying degrees of linear redshift. The sensitivity coefficients of each parameter to the resonance wavelength are obtained through linear fitting as follows: For every 1 nm increase in radius R, the resonant peak wavelength redshifts by approximately 1.885 nm.

[0039] For every 1 nm increase in height h, the resonant peak wavelength redshifts by approximately 1.306 nm.

[0040] For every 1 nm increase in the side length Px, the resonant peak wavelength redshifts by approximately 0.337 nm.

[0041] For every 1nm increase in the side length Py, the resonant peak wavelength redshifts by approximately 0.336nm.

[0042] The results show that the size (especially the radius R) of the double-notched silicon nanodisk 2 is the most important factor in tuning the resonant wavelength, while the side lengths Px and Py of the array units have a relatively weak influence. This analysis demonstrates that the metasurface sensor structure of the present invention has good tunability and provides an important reference for process tolerance and target wavelength design in actual fabrication.

[0043] The disc-shaped double-notch multifunctional metasurface sensor of this invention possesses high-precision dual sensing capabilities for refractive index and temperature. The refractive index sensing sensitivity of the disc-shaped double-notch multifunctional metasurface sensor is no less than 363.5 nm / RIU. As the refractive index of the analyte gradually increases from 1.0, the resonance peak undergoes a linear redshift. When the refractive index of the analyte exceeds 2.0, the resonance peak for sensing by the metasurface disappears. Therefore, the sensing refractive index range is 1.0 to 2.0, suitable for detecting gaseous and / or liquid substances. Simultaneously, the disc-shaped double-notch multifunctional metasurface sensor is also used for temperature sensing, with a temperature sensing sensitivity of no less than 51.96 pm / ℃ and a sensing temperature range of 20℃ to 80℃.

[0044] Even minute changes in the refractive index or temperature of the environment in which the metasurface sensor operates can cause corresponding alterations in the transmission spectrum, specifically manifested as varying degrees of redshift or blueshift. The refractive index sensitivity of the metasurface sensor can be defined as the change in the resonant wavelength Sn of the resonance peak caused by each unit change in refractive index, expressed as: .in, Indicates wavelength change. This indicates the change in refractive index.

[0045] The temperature sensitivity ST of a metasurface sensor can be defined as follows: . It indicates a change in temperature.

[0046] The refractive index sensitivity Sn and the temperature sensitivity ST can be obtained separately through... Figure 7 and Figure 8 The slope of the linear fit is calculated.

[0047] In practical applications, refractive index and temperature often change simultaneously, and there is a coupling effect between them (e.g., temperature changes cause changes in the material's refractive index). Therefore, the total change in resonant wavelength can be expressed as: ; in, This indicates the direct effect of changes in refractive index on wavelength; This indicates the direct effect of temperature change on wavelength; it also indicates the indirect effect of temperature on wavelength by changing the refractive index. express The thermo-optic coefficient of the substance to be tested.

[0048] The above discussion on refractive index and sensitivity is based on the bivariate variation of refractive index and temperature. However, in practical applications, refractive index and temperature often change simultaneously, and there is a coupling effect between them. For example, temperature changes can alter the refractive index of the sensor material and the surrounding medium through the thermo-optic effect. The relationship between the material's refractive index and temperature can be described by the thermo-optic effect, and its expression is: ; in, η The thermo-optic coefficient of the material is represented by n(T), and the refractive index of the material at the current temperature is represented by n(T). This represents the refractive index of the material at the reference temperature. The thermo-optical coefficients of water, silicon dioxide, and silicon are -1.02 × 10⁻⁶. -4 / K, 8.6×10 -6 / K, 1.84×10 -4 / K.

[0049] A disk-shaped, double-notch, multifunctional metasurface sensor is used for wide-band response. CST simulation verification shows that the sensor can excite significant Fano resonance phenomena in the spectral band from 900 nm to 2500 nm, indicating that it has excellent sensing capabilities in this wide band.

[0050] The disk-shaped double-notch multifunctional metasurface sensor is used as a polarization-type optical switch. By changing the polarization angle of the incident light, the transmission intensity of the magnetic dipole Fano resonance can be changed, thereby realizing the opening and closing of the optical path.

[0051] When the metasurface sensor of this invention is used as a polarization-modulated optical switch device, the incident light is gradually converted from Y-polarization to X-polarization (i.e., the polarization angle is increased from 0° to 90°). Figure 9 As shown, the resonance peak gradually decreases as the polarization angle increases within the range of 0° to 45°, and disappears completely at 45°. When the polarization angle continues to increase from 45° to 90°, the modulation depth of the resonance peak gradually increases again, and its transmission spectral characteristics are basically symmetrical to the trend when the angle is less than 45°. In summary, by changing the polarization state of the incident light, the generation and disappearance of the resonance peak can be controlled, thereby realizing the optical path switching function at a specific wavelength.

[0052] The surface of the double-notched silicon nanodisk 2 is provided with a specific gas-sensitive film for gas volume fraction detection. The specific gas-sensitive film is either a cryptoalkyl A molecule methane gas-sensitive film or a palladium-tungsten oxide hydrogen gas-sensitive film. When used for methane gas volume fraction detection, the sensitivity of the double-notched multifunctional metasurface sensor is no less than -1.53 ​​nm / %. When used for hydrogen gas integral fraction detection, the sensitivity is no less than -0.44 nm / .

[0053] To achieve volume fraction sensing of specific gases, a specific gas-sensitive thin film needs to be deposited on top of the existing double-layer dielectric metasurface sensor using capillary dip-coating technology. A cryptoethane A methane gas-sensitive film and a palladium-tungsten oxide hydrogen gas-sensitive film were employed. Figure 10 and Figure 11 As shown, both materials are insensitive to temperature and humidity, and their refractive index decreases linearly with increasing gas volume fraction (within the range of 0% to 3%), as shown in the following relationship: NCH4 = 1.4478 - 0.038 CCH4; NH2 = 1.995 - 0.00067 CH2; Where N is the effective refractive index of the gas-sensitive membrane; C is the gas volume fraction. The corresponding gas volume fraction value can be calculated by measuring the refractive index of the gas-sensitive membrane.

[0054] like Figure 12 As shown, a method for fabricating a disk-shaped double-notch multifunctional metasurface sensor includes the following steps: S1: The three-inch quartz substrate 1 is cleaned with acetone and deionized water and then dried with nitrogen.

[0055] S2: An amorphous silicon film is deposited on the cleaned quartz substrate 1 using plasma-enhanced chemical vapor deposition (PECVD). In this embodiment, an ellipsometry is used to measure the film thickness to ensure that the silicon film meets the design requirements.

[0056] S3: A tackifier, a positive photoresist, and a conductive adhesive are sequentially coated onto a quartz substrate 1 on which an amorphous silicon film has been deposited.

[0057] Specifically, firstly, hexamethyldisilazane (HMDS) is applied to enhance the adhesion between the photoresist and the substrate; secondly, ZEP520 positive photoresist is coated onto the sample surface using a spin coater at 3000 rpm; then, AR-PC conductive adhesive is applied to the photoresist surface to eliminate charge accumulation, and the sample is placed in the solution for drying. This step requires careful handling away from light.

[0058] S4: Define nanostructure patterns using electron beam lithography, and then develop and fix them.

[0059] Specifically, an electron beam exposure device is used to define the nanostructure patterns and regions. After exposure, the conductive adhesive is washed away with deionized water. The sample is developed with ZED-N50 developer and then fixed with deionized water. The sample chip is then dried with nitrogen gas.

[0060] S5: The pattern is transferred to the silicon layer by inductively coupled plasma-reactive ion etching (ICP-RIE) to form a periodic array of double-notched silicon nanodisks.

[0061] S6: Remove residual photoresist and byproducts to obtain a disk-shaped double-notch multifunctional metasurface sensor.

[0062] Residual photoresist and etching byproducts were removed by immersion in acetone followed by rinsing with deionized water. The resulting metasurface sensor, dried with nitrogen, can then be used for multi-parameter sensing applications of refractive index and temperature.

[0063] A method for fabricating a gas volume fraction detection sensor includes the following steps: coating a specific gas-sensitive thin film onto the upper surface of a disk-shaped double-notch multifunctional metasurface sensor using a capillary dip-coating process.

[0064] To achieve the gas volume sensing function of the metasurface, a specific gas-sensitive thin film is deposited on the surface of the double-notched silicon nanodisk 2 using capillary dip-coating technology for gas volume fraction detection.

[0065] To illustrate the technical effects of the metasurface sensor of this invention in detail, the following will verify and analyze its sensing performance using CST simulation software based on the finite-time integration method, in conjunction with the accompanying drawings and specific embodiments.

[0066] In the context of water's refractive index (1.33), based on Figure 7 The sensing performance of the designed metasurface sensor was evaluated in the refractive index range of 1.30 to 1.40. Calculations show that the sensor achieves a liquid sensitivity of 363.5 nm / RIU, and its theoretical maximum quality factor (Q factor) at the resonance peak can reach 1.6 × 10⁻⁶. 5 The theoretical maximum value of FOM can reach 36350.

[0067] Considering the feasibility of actual process preparation, the asymmetry factor was finally selected. The corresponding structural parameters are: the width of the first notch 21 is 220 nm and the distance to the center of the disk is 140 nm; the width of the second notch 22 is 200 nm and the distance to the center of the disk is 150 nm. Under these parameters, the quality factor of the metasurface sensor is 6253 and the quality factor (FOM) is 1403.

[0068] When the metasurface sensor of the present invention is used as a temperature sensor, assuming the substance to be measured is water, and considering the thermo-optic effects of the material of the quartz substrate 1 (silicon dioxide) and the material of the double-notched silicon nanodisk 2 (silicon), the functional relationship between the refractive index of the material and temperature can be expressed as: ; in, η The thermo-optic coefficient of the material is represented by n(T), and the refractive index of the material at the current temperature is represented by n(T). This represents the refractive index of the material at the reference temperature. The thermo-optical coefficients of water, silicon dioxide, and silicon are -1.02 × 10⁻⁶. -4 / K, 8.6×10 -6 / K, 1.84×10 -4 / K.

[0069] like Figure 8 This indicates that the temperature sensing performance of the metasurface of the present invention is such that, between 20°C and 80°C, the resonance peak redshifts by 3.03 nm from its initial position as the temperature increases. Its temperature sensing sensitivity can reach 51.96 pm / °C.

[0070] When the metasurface sensor of the present invention is used as a polarization-controlled optical switch device, the incident light is gradually changed from Y polarization to X polarization (i.e., the polarization angle is increased from 0° to 90°), as shown below. Figure 9 As shown, the resonance peak gradually decreases as the polarization angle increases within the range of 0° to 45°, and disappears completely at 45°. When the polarization angle continues to increase from 45° to 90°, the modulation depth of the resonance peak gradually increases again, and its transmission spectral characteristics are basically symmetrical to the trend when the angle is less than 45°. In summary, by changing the polarization state of the incident light, the generation and disappearance of the resonance peak can be controlled, thereby realizing the optical path switching function at a specific wavelength.

[0071] like Figure 10 and Figure 11 As shown, after coating the metasurface sensor with a corresponding gas-sensitive film (such as a methane gas-sensitive film or a palladium-tungsten oxide hydrogen gas-sensitive film), the transmission spectrum exhibits varying degrees of blue shift as the volume fraction of methane (or hydrogen) increases from 0% to 1%, 2%, and 3%. Fitting calculations show that the sensing sensitivity for methane volume fraction is -1.53 ​​nm / %, and the sensing sensitivity for hydrogen volume fraction is -0.44 nm / %.

[0072] Metasurfaces can be understood as specially designed subwavelength two-dimensional materials. By arranging and optimizing the micro- and nano-structures of the devices, reflection or transmission in a specific optical band can be achieved, thereby generating spectral resonance peaks. Different structural and dimensional designs, as well as different ways of breaking structural symmetry, result in different characteristics of the excited Fano resonance peaks, and thus different effects on mode coupling and electric field modulation.

[0073] The disk-shaped, double-notch, multifunctional metasurface sensor of this invention generates a peak sensing position at 1617 nm. By breaking the asymmetry between the first notch 21 and the second notch 22, a Fano resonance peak dominated by magnetic dipoles (MD) is excited. This resonance peak exhibits excellent refractive index sensing performance, with a refractive index sensing sensitivity of up to 363.5 nm / RIU, and also possesses polarization-type optical switching characteristics. Simultaneously, based on the inherent thermo-optical effect of silicon dioxide and silicon materials (the thermo-optical coefficients of silicon dioxide and silicon materials are 8.6 × 10⁻⁶ and 8.6 × 10⁻⁶ respectively), [further details about the sensor are needed to complete the translation]. -6 / K, 1.84×10 -4 / K。), this sensor achieves a temperature sensing value of 51.96 pm / ℃. Furthermore, by modifying the metasurface with a specific gas-sensitive thin film, the mechanism of refractive index change after physical adsorption of gas can be utilized to achieve sensitive detection of gases such as methane and hydrogen. In summary, as shown in Table 1, the sensor of this invention, with its high sensitivity, high quality factor, and multifunctional integration characteristics, successfully achieves multi-purpose sensing in a gas-liquid two-phase environment.

[0074] Table 1. Functional Comparison of the Circular Double-Notch Multifunctional Metasurface Sensor with Existing Sensors:

[0075] In summary, the metasurface sensor proposed in this invention has advantages such as simple operation, low experimental requirements, and low fabrication cost. Its sensor structure can be fabricated with only a single etching process, significantly simplifying the manufacturing process. Compared with traditional metal metasurface sensors, this approach uses all-dielectric materials, significantly reducing optical loss and exhibiting higher sensitivity and a wider detection range in refractive index detection.

[0076] In terms of functional expansion, this invention breaks through the limitations of traditional single-parameter detection, realizing simultaneous measurement of multiple parameters and detection of multiple phases (gas and liquid), greatly expanding practical application scenarios and enabling its widespread application in fields such as environmental monitoring, biomedical detection, and optical switch control. Furthermore, this device possesses direct detection capabilities, eliminating the need for pretreatment of original samples (such as serum, buffer solutions, microbial cultures, etc.) such as dilution, centrifugation, and labeling, significantly improving detection efficiency and practicality.

[0077] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A disk-shaped, double-notch, multifunctional metasurface sensor, characterized in that, include: A quartz substrate, and periodically arranged double-notched silicon nanodiscs disposed on the quartz substrate; The double-notched silicon nanodisk includes a first notch and a second notch, the openings of the first notch and the second notch are oriented in opposite directions, and both openings are oriented at a 45° angle to the side length direction of the quartz substrate. The first and second notches have different geometric dimensions and / or positions to enable the double-notched silicon nanodisk to form an asymmetric structure for exciting Fano resonance based on magnetic dipoles to achieve sensing functionality.

2. The disk-shaped double-notch multifunctional metasurface sensor according to claim 1, characterized in that, The width of the first notch is not equal to the width of the second notch; and / or, the distances from the first notch and the second notch to the center of the double-notch silicon nanodisk are not equal.

3. A disk-shaped double-notch multifunctional metasurface sensor as described in claim 1 or 2, characterized in that, It is used to realize at least one of the following functions: gas-liquid compatible sensing, temperature sensing, broadband sensing, and polarization-type optical switching.

4. A gas volume fraction detection sensor, characterized in that, Includes the disc-shaped double-notch multifunctional metasurface sensor as described in claim 1 or claim 2, wherein a specific gas-sensitive thin film is disposed on the surface of the disc-shaped double-notch multifunctional metasurface sensor.

5. The gas volume fraction detection sensor according to claim 4, characterized in that, The specific gas-sensitive film is a cryptoalkyl A molecule methane gas-sensitive film or a palladium-tungsten oxide hydrogen gas-sensitive film.

6. A method for fabricating a disk-shaped double-notch multifunctional metasurface sensor as described in claim 1 or 2, characterized in that, Includes the following steps: S1: Clean the quartz substrate; S2: Amorphous silicon film is deposited on a cleaned quartz substrate using plasma-enhanced chemical vapor deposition (PECVD). S3: A tackifier, a positive photoresist, and a conductive adhesive are sequentially coated onto a quartz substrate on which an amorphous silicon film has been deposited. S4: Define nanostructure patterns using electron beam lithography, and then develop and fix them; S5: The pattern is transferred to the silicon layer by inductively coupled plasma-reactive ion etching technology to form a periodic array of double-notch silicon nanodisks. S6: Remove residual photoresist and byproducts to obtain a disk-shaped double-notch multifunctional metasurface sensor.

7. A method for preparing a gas volume fraction detection sensor as described in claim 4 or 5, characterized in that, Includes the following steps: A specific gas-sensitive thin film is coated onto the upper surface of the disc-shaped double-notch multifunctional metasurface sensor using a capillary dip-coating process.

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