A composite resonant cavity structure based on fano resonance of MDM nanocavity coupled two-dimensional transition metal sulfide and a preparation method thereof

Abstract

The application belongs to the technical field of photoelectric regulation, and particularly relates to a composite resonant cavity structure of MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance and a preparation method thereof. The application provides a composite resonant cavity structure of MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance, in the MDM nanocavity, the material of the dielectric layer comprises one or more of hexagonal boron nitride and indium tin oxide, and the two-dimensional transition metal sulfide comprises tungsten disulfide. The MDM nanocavity comprises, in sequence, a metal layer a, a hexagonal boron nitride layer, an indium tin oxide layer and a metal layer b; and the material of the metal layer comprises one or more of silver, titanium, chromium and gold. The application adopts the optical film system design idea and the efficient preparation method of the MDM nanocavity coupled TMD atomic layer, and produces a multi-path tunable optical reflection spectrum Fano resonance. The quality factor and intensity of the Fano resonance of the application are far ahead of those of other similar structures.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optoelectronic regulation, and particularly relates to a composite resonant cavity structure of MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance and a preparation method thereof. BACKGROUND

[0002] In optical reflectivity, Fano resonance is a phenomenon of asymmetric spectral line shape caused by interference between discrete states and continuous states. This phenomenon appears in optical reflectivity as a reflection peak with specific asymmetry when light waves interact with specific structures such as photonic crystals, waveguides, or nanostructures due to interference between resonance modes. This asymmetry is caused by the coupling between discrete states (narrow-band localization) and continuous states (wide-band background), resulting in sharp, asymmetric reflectivity changes near the resonance frequency.

[0003] MDM cavity, i.e. Metal-Dielectric-Metal cavity, is an optical resonance structure composed of two metal layers and a dielectric layer sandwiched in between. MDM cavity exhibits strong optical resonance characteristics, mainly due to the excitation of surface plasmon polaritons (SPPs) in its structure. The unique optical properties of SPPs make the Fano resonance effect produced by MDM cavity extremely sensitive to environmental changes. Further, tunable spectral Fano resonance can be achieved by changing one or more structural properties. For example, HUA LU et al. disclosed in "Exciton-induced Fano resonance in metallic nanocavity with tungsten disulfide atomic layer" (Optics Express, 2023, 31(13), 20761-20768) that weak coupling Fano resonance and asymmetric spectral response appear when ultra-thin MDM cavity is integrated with two-dimensional ultra-thin nanometer transition metal sulfide material (TMDs), and the resonance wavelength of the MDM nanocavity can be controlled by adjusting the thickness of the dielectric layer.

[0004] However, this method still has the following disadvantages: the tunable range of Fano resonance is too narrow, because the structure is not suitable for applying an external electric field to perform band regulation engineering on TMDs; and the thickness and optical properties of the metal layer and the dielectric layer are relatively fixed after the device is prepared, so the background reflection spectrum of the MDM cavity is relatively fixed after the device is prepared, and it is difficult to achieve good tuning of the coupling strength of Fano resonance; in addition, the resonance strength produced by the above-mentioned reference method is relatively small, which cannot be well applied in practical applications. SUMMARY

[0005] In view of the existing problems, the application provides a new method for optical device design, a composite device structure based on multi-path tunable Fano resonance is prepared by using MDM nanocavity coupled TMDs atomic layer, and a Fano resonance reflection spectrum is generated, so that a metamaterial and a metasurface structure with specific optical characteristics, such as an optical switch, a bio-chemical sensor and the like, can be designed.

[0006] In order to solve the above technical problems, the application provides the following technical scheme:

[0007] The application provides a composite resonant cavity structure of MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance, the MDM nanocavity comprises a dielectric layer and a metal layer; the material of the dielectric layer comprises one or more of hexagonal boron nitride and indium tin oxide; the two-dimensional transition metal sulfide comprises tungsten disulfide.

[0008] Further, the MDM nanocavity comprises, in sequence, a metal layer a, a hexagonal boron nitride layer, an indium tin oxide layer, and a metal layer b; the material of the hexagonal boron nitride layer comprises hexagonal boron nitride; the material of the indium tin oxide layer comprises indium tin oxide; the material of the metal layer a comprises one or more of silver, titanium, chromium and gold; and the material of the metal layer b comprises one or more of silver, titanium, chromium and gold.

[0009] Further, the composite resonant cavity structure comprises, in sequence, a silver layer a, the hexagonal boron nitride layer, a tungsten disulfide layer, the indium tin oxide layer, and a silver layer b; the material of the tungsten disulfide layer comprises tungsten disulfide; and the materials of the silver layer a and the silver layer b both comprise silver.

[0010] Further, the thickness of the silver layer a comprises 5-15 nm, the thickness of the hexagonal boron nitride layer comprises 25-75 nm, the thickness of the tungsten disulfide layer comprises 0.7-10 nm, the thickness of the indium tin oxide layer comprises 8-20 nm, and the thickness of the silver layer b comprises 20-50 nm.

[0011] Preferably, the thickness of the hexagonal boron nitride layer comprises 30-60 nm.

[0012] Preferably, the tungsten disulfide layer comprises three layers of WS2 atomic layers.

[0013] Preferably, the thickness of the silver layer a comprises 8.5 nm.

[0014] Further, the composite resonant cavity structure further comprises a silicon wafer substrate; the silicon wafer substrate comprises a SiO2 layer attached to one side of a Si layer; and the silicon wafer substrate is attached to the outer side of the silver layer b by the SiO2 layer.

[0015] Accordingly, the present invention also provides a method for preparing the above-mentioned composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides, comprising the following steps:

[0016] S1. The silver layer b is grown using a vacuum evaporation deposition method;

[0017] S2. The indium tin oxide layer is grown on the surface of the silver layer b using magnetron sputtering deposition.

[0018] S3. Prepare the tungsten disulfide layer on the surface of the indium tin oxide layer using a mechanical stripping method;

[0019] S4. Prepare the hexagonal boron nitride layer on the surface of the tungsten disulfide layer using a mechanical stripping method;

[0020] S5. The silver layer a is grown on the surface of the hexagonal boron nitride layer by vacuum evaporation deposition to obtain the composite resonant cavity structure.

[0021] Furthermore,

[0022] Step S3 includes the following steps:

[0023] S3-1. Prepare two-dimensional tungsten disulfide sheets on the surface of PDMS film.

[0024] S3-2. Transfer the two-dimensional tungsten disulfide sheet to the surface of the indium tin oxide layer to obtain the tungsten disulfide layer;

[0025] Step S4 includes the following steps:

[0026] S4-1. Two-dimensional hexagonal boron nitride sheets are prepared on the surface of PDMS thin film.

[0027] S4-2. Transfer the two-dimensional hexagonal boron nitride sheet to the surface of the tungsten disulfide layer to obtain the hexagonal boron nitride layer.

[0028] Furthermore,

[0029] Step S3-1 specifically involves: placing the tungsten disulfide block onto the adhesive material, repeatedly adhering and peeling it off to obtain a tungsten disulfide layered sheet; then attaching the tungsten disulfide layered sheet onto the PDMS film, peeling off the adhesive material to obtain a two-dimensional tungsten disulfide sheet;

[0030] Step S3-2 specifically involves: attaching the PDMS film to the surface of the indium tin oxide layer, so that the two-dimensional tungsten disulfide sheet is attached to the indium tin oxide layer; heating the entire structure when the PDMS film is completely attached to the surface of the indium tin oxide layer; and then peeling off the PDMS film to obtain the tungsten disulfide layer.

[0031] The step S4-1 is specifically: placing the hexagonal boron nitride bulk on an adhesive material, repeatedly pasting and peeling, and obtaining a hexagonal boron nitride layered sheet; then attaching the hexagonal boron nitride layered sheet to a PDMS film, peeling off the adhesive material, and obtaining a two-dimensional hexagonal boron nitride sheet.

[0032] The step S4-2 is specifically: attaching the PDMS film to the surface of the tungsten disulfide layer, attaching the two-dimensional hexagonal boron nitride sheet to the tungsten disulfide layer, and heating the whole when the PDMS film is completely attached to the surface of the tungsten disulfide layer; then peeling off the PDMS film, and obtaining the hexagonal boron nitride layer.

[0033] Further, in the step S3-2 or the step S4-2, the temperature of the whole heating is 60℃, and the time of the whole heating is 5 min.

[0034] Further, in the step S1, the growing device is a vacuum evaporation film coating device; in the step S5, the growing device is a vacuum evaporation film coating device; in the step S1, the growing rate is less than 0.5 nm / s, and the vacuum degree of the growing is less than 10 -5 Pa; in the step S5, the growing rate is less than 0.5 nm / s, and the vacuum degree of the growing is less than 10 -5 Pa.

[0035] In the step S2, the growing device is a magnetron sputtering film coating device; in the step S2, the growing conditions include: the atmosphere is pure argon, the vacuum degree is less than 10 -4 Pa, the temperature is 295℃, the sputtering voltage is 40V, and the target material is indium tin oxide; the purity of the target material is 99.99%; and the doping ratio of the target material is In2O3: SnO2=9:1.

[0036] Further, in the step S1, the silver layer b is grown on a silicon wafer substrate; the thickness of the SiO2 includes 250-350 nm; and before the step S1, the silicon wafer substrate is subjected to surface cleaning.

[0037] Further, the above silicon wafer substrate is single-sidedly oxidized, the thickness of the SiO2 (oxidation layer) is 285±5 nm, and the thickness of the silicon single crystal is 1 mm.

[0038] Further, in the step S3-1 or the step S4-1, the adhesive material includes a blue film.

[0039] Further, in the step S3-1 or the step S4-1, peeling off the adhesive material includes slowly peeling off the adhesive material.

[0040] Further, the adhesion rate / peeling rate of the PDMS film in step S3-2 or step S4-2 is lower than 5 microns per second, so as to improve the success rate of mechanical transfer.

[0041] Further, the silicon wafer substrate is a single-side silicon oxide wafer (SiO2 / Si), and the structure is that a 285±5nm oxide layer (SiO2) is attached on a single crystal silicon (Si) layer (Si).

[0042] Further, the flatness of the surface (SiO2 air contact surface) of the silicon wafer substrate is about 2nm.

[0043] The application adopts the optical film system design idea and efficient preparation method of MDM nanocavity coupled TMDs atomic layer, and produces a multi-path tunable optical reflection spectrum Fano resonance.

[0044] In the optical nanoresonator, the coupling effect of photons and excitons has been a research hotspot in the field, which has important application value and industrialization prospect in spectrum control. The composite resonant cavity structure of the application is based on two-dimensional ultrathin nanometer transition metal sulfide material (TMDs) coupled metal-dielectric-metal (MDM) nanocavity. The composite resonant cavity structure produces reflection spectrum Fano resonance. The MDM cavity structure used in the application is silver (Ag)-indium tin oxide (ITO)-hexagonal boron nitride (h-BN)-silver (Ag).

[0045] The application develops a brand new method of integrating MDM with TMDs. In the method, the dielectric material in the MDM cavity is replaced with a tunable dielectric layer, such as a temperature phase change material, to solve the technical problem that the background reflection spectrum is difficult to tune. If the dielectric material in the MDM cavity is all replaced with a material with good conductivity as the dielectric layer, the structure is completely conductive, and the optical properties such as spectrum background cannot be controlled.

[0046] The dielectric layer in the MDM cavity of the application uses h-BN, which has high optical transmittance and high chemical and physical stability. However, using traditional coating methods will cause different degrees of damage to the atomic layer TMDs exciton absorption effect due to various physical and chemical reasons (high temperature, gas pollution, breakdown, etc.), which can completely disable the TMDs. The dry mechanical transfer method used in the application is non-invasive and does not require external conditions, so the damage to the TMDs material is almost negligible.

[0047] The dielectric layer in the MDM cavity of the composite resonant cavity structure uses ITO / h-BN two-layer material, and the structure is ITO / TMDs / h-BN after coupling with TMDs, compared with the coupling structure of ITO / TMDs / ITO, the present application realizes more complex functions and better performance by changing the uniformity and continuity of the metal layer and the dielectric layer, including Fano resonance spectral intensity, quality factor, resonance line width, and also including flexibility such as realizing multi-physical field (electric, magnetic, temperature) regulation. On this basis, the scene applicability / economy / stability / performance of the structure can be further improved through experiments and theoretical simulation.

[0048] The following aspects are considered in the selection of TMDs and structure design: TMDs have atomic-level flatness and thickness; TMDs have strong exciton effect at room temperature - large exciton binding energy to produce strong enough absorption peaks to produce Fano resonance through coupling MDM cavity; after coupling, the electronic band structure is tunable - by changing the temperature / chemical composition, or applying an external electric field, the energy band structure can be adjusted and the electronic and optical properties can be changed to produce tunable Fano resonance; the layer-dependent optical and electronic properties provide a certain degree of flexibility for device design and optimization.

[0049] Regarding the preparation aspect: the intensity of the prior art Fano resonance does not reach a very high level, because the TMDs have not reached the ideal exciton absorption intensity, the present application finds a more optimal preparation process through experiments and simulation; the ITO layer of the present application is prepared by magnetron sputtering, and the surface flatness is between 2-5 nanometers, which makes the step of transferring atomic layer TMDs to the ITO layer difficult to implement, the present application solves this problem by optimizing the parameters and performance of the magnetron sputtering equipment; the complexity of the overall device preparation is high, because the preparation and integration process of the ultrathin nanometer multilayer structure is complex, the present application solves this problem by optimizing the preparation and integration process and optimizing the device structure.

[0050] In summary, in view of the above problems in the field of nanophotonics, the present application proposes an innovative spectrum regulation scheme. The present application creatively designs a new type of optical resonant cavity device structure, integrates atomically thin tungsten disulfide (WS2) in a metal-dielectric-metal (MDM) nanocavity, and successfully realizes precise regulation of Fano resonance. The high consistency of experimental results and numerical simulation confirms the existence of tunable asymmetric Fano resonance spectrum, which fully meets the theoretical prediction.

[0051] Compared with the prior art, the implementation of the present application has the following beneficial effects:

[0052] 1. The quality factor and intensity of Fano resonance in the reflection spectrum generated by the composite resonant cavity structure of the MDM nanocavity coupled with two-dimensional transition metal sulfide based on Fano resonance of the application are superior to those of other similar structures.

[0053] 2. On the basis of the discovery that the resonance wavelength, line width and quality factor (q factor) can be accurately controlled by temperature or MDM cavity medium layer thickness, the application realizes accurate control of Fano resonance by controlling the medium layer thickness; at the same time, the two-dimensional atomic layer TMDs coupled with the MDM cavity multi-physical field spectrum simulation under different conditions further confirms that the composite resonant cavity structure of the MDM nanocavity coupled with two-dimensional transition metal sulfide based on Fano resonance of the application has excellent scalability, laying a solid foundation for future industrial application.

[0054] 3. The real-time tunability of Fano resonance under the composite resonant cavity structure of the MDM nanocavity coupled with two-dimensional transition metal sulfide based on Fano resonance of the application is creatively proposed, which opens up a new way for optical adjustable Fano resonance. The application integrates various materials with adjustable optical properties, creating a new way for the integration of more complex and miniaturized Fano resonance multi-field tuning systems.

[0055] 4. The total thickness of the composite resonant cavity structure of the MDM nanocavity coupled with two-dimensional transition metal sulfide based on Fano resonance of the application is at the level of 100 nanometers. At this nanometer scale level, the integrable characteristics of the device are effectively utilized, and the performance of the device is optimized through longitudinal (vertical stacking) and transverse (horizontal integration) expansion, achieving better performance parameter indicators and flexibility.

[0056] 5. The Fano resonance generated by the composite resonant cavity structure of the MDM nanocavity coupled with two-dimensional transition metal sulfide based on Fano resonance of the application can improve spectral resolution and sensing sensitivity, and plays an important role in the fields of optical modulation, filtering, enhanced spectrum, optical non-reciprocal transmission, etc.

[0057] 6. The application has high integration with the prior art. The sample preparation process of the composite resonant cavity structure technology of the application can be standardized and streamlined, which is more convenient for technicians to prepare. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The preparation process and test analysis flowchart of the composite resonant cavity structure of the application;

[0059] Figure 2 The preparation process and flowchart of each layer of the composite resonant cavity structure of the application;

[0060] Figure 3A three-dimensional structural diagram of the composite resonant cavity structure of the present application;

[0061] Figure 4 A schematic diagram of the atomic layer TMDs coupled nano MDM optical cavity structure of the composite resonant cavity structure of the present application;

[0062] Figure 5 A schematic diagram of the spectrum response measurement system of the present application;

[0063] Figure 6 A temperature-dependent reflection spectrum test diagram of the composite resonant cavity structure (Si / SiO2 / Ag / ITO / WS2 / h-BN / Ag) of the present application;

[0064] Figure 7 A reflection spectrum Fano resonance under temperature tuning and its theoretical fitting observed in the effect example experiment of the present application;

[0065] Figure 8 An exciton absorption model diagram in the WS2 atomic layer coupled MDM cavity of the present application;

[0066] Figure 9 An optical microscopic image of the composite resonant cavity structure of the present application;

[0067] Figure 10 A simulation experiment and theoretical fitting of the Fano resonance multi-field tuning characteristics generated by the composite resonant cavity structure of the present application;

[0068] Figure 11 A two-dimensional material exfoliation schematic diagram;

[0069] Figure 12 A two-dimensional material transfer system schematic diagram. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with specific embodiments and drawings. Unless specifically stated, the reagents and materials used below are commercially available products.

[0071] In the following examples, the preparation process and test analysis flowchart of the composite resonant cavity structure of the MDM nano cavity coupled two-dimensional transition metal sulfide based on Fano resonance are shown in Figure 1 , and the preparation flowchart of each layer is shown in Figure 2 .

[0072] Example 1

[0073] The silicon wafer substrate is surface cleaned, and the silicon wafer substrate includes a two-layer structure: the thickness of the oxide layer, i.e., the SiO2 layer, is 285 ± 5 nm; and the thickness of the silicon single crystal, i.e., the Si layer, is 1 mm (single-side oxidation). The specific implementation steps are as follows: the silicon wafer substrate is placed in anhydrous ethanol for ultrasonic cleaning for 10 min; then placed in an acetone solution for ultrasonic cleaning for 5 min; then the silicon wafer substrate is soaked in an isopropyl alcohol solution for 2 min; and finally, the surface of the silicon wafer substrate is dried and cleaned by using high-pressure nitrogen flushing.

[0074] Example 2

[0075] A vacuum evaporation film coating device is used to evaporate and grow an Ag thin film with a thickness of 31.5 nm on the SiO2 layer surface of the silicon wafer substrate processed in Example 1, to obtain a silver layer b. The preparation conditions are as follows: the growth rate should be kept stable, the growth rate should be less than 0.5 nm / s, and the atmosphere environment in which the silicon wafer substrate is placed during growth should have a vacuum degree less than 10 -5 Pa.

[0076] Example 3

[0077] A magnetron sputtering film coating device is used to sputter and grow an indium tin oxide (ITO) thin film with a thickness of 12.5 nm on the silver layer b obtained in Example 2, to obtain an indium tin oxide layer. The sputtering conditions are as follows: pure argon atmosphere, vacuum degree less than 10 -4 Pa, temperature 295°C (degrees Celsius), sputtering voltage 40 volts (V), and target material selected: ITO; purity 99.99%; doping ratio: In2O3: SnO2 = 9:1.

[0078] Example 4

[0079] (1) As shown in Figure 11 , a two-dimensional material, i.e., a tungsten disulfide (WS2) layered sheet, is prepared using a mechanical exfoliation method. The specific implementation steps are as follows: a blocky two-dimensional material, tungsten disulfide, is placed on a mechanical exfoliation special adhesive tape blue film; the blocky material is repeatedly pasted and peeled off; the blocky material is changed into a layered sheet; the layered sheet on the adhesive tape is transferred to a flexible substrate PDMS (polydimethylsiloxane) film, and after standing for a period of time, the blue film is slowly peeled off from above the PDMS film, so that the target sample remains on the surface of the PDMS film.

[0080] (2) The WS2 atomic layer is transferred to the surface of the indium tin oxide layer to prepare a tungsten disulfide layer. The specific implementation steps are as follows: an optical microscope is used to find the target sample on the surface of the PDMS film and to perform physicochemical characterization; a high-precision electromechanical integrated three-axis displacement table is used in cooperation with a metallographic optical microscope to position and observe the transfer of the target sample to the surface of the ITO film obtained in Example 3 (see Figure 12) ; the adhesion / peeling rate of the PDMS film should be as low as possible, less than 5 microns per second to improve the success rate of mechanical transfer; when the surface of the PDMS film containing the target material is completely attached to the surface of the ITO film, the whole is heated to 60 degrees Celsius for 5 minutes to improve the success rate of transfer and the surface flatness of the WS2 atomic layer. Finally, a WS2 layer is obtained as 3 layers of WS2 atomic layers.

[0081] Example 5

[0082] (1) As shown in Figure 11 , a two-dimensional material, i.e. a hexagonal boron nitride (h-BN) layered sheet, is prepared using a mechanical exfoliation method and attached and retained on the surface of a PDMS film.

[0083] (2) The hexagonal boron nitride layered sheet is transferred and completely covers the surface of the tungsten disulfide layer in Example 4 (see Figure 12 for a schematic diagram of positioning and transferring the target sample), forming a coupling region to prepare a hexagonal boron nitride layer. Finally, the thickness of the obtained hexagonal boron nitride layer is 30-55 nm.

[0084] The material used in this example is a bulk two-dimensional material, hexagonal boron nitride, and the target layer for transfer is a tungsten disulfide layer. The rest of the preparation method is the same as that for the preparation of the tungsten disulfide layer in Example 4.

[0085] Example 6

[0086] In this example, an 8.5 nm thick Ag film is evaporated and grown on the hexagonal boron nitride layer obtained in Example 5, and the rest of the preparation method and preparation conditions are the same as those in Example 2, to obtain a silver layer a, and finally the whole obtains a composite resonant cavity structure of MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance (Si / SiO2 / Ag / ITO / WS2 / h-BN / Ag).

[0087] The three-dimensional structure diagram of the composite resonant cavity structure of MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance is shown in Figure 3 ; wherein d1 / d2 / dw / d3 / d4 / d5 respectively represent Ag / h-BN / WS2 / ITO / Ag / SiO2, and the actual thicknesses of d1 / d2 / dw / d3 / d4 / d5 are 8.5 / 55 / 2.4 / 12.5 / 31.5 / 285 nm respectively; the color arrows represent the incidence and emission of the mixed wavelength beam. Figure 4 is a schematic diagram of an atomic layer TMDs coupled nanometer MDM optical cavity structure, and the relationship between the metal layer, the dielectric layer and the TMDs is shown in Figure 4 .

[0088] Test Example

[0089] Take the MDM nanocavity coupled two-dimensional transition metal sulfide based on Fano resonance in Example 6 as the test sample, and perform spectral measurement analysis on the sample, and further perform temperature tuning spectral measurement analysis, electric field regulation spectral measurement analysis, etc.

[0090] The spectral response measurement system is shown in FIG. 1. Figure 5 The optical response system is composed of a light source, an optical fiber, an optical pinhole, an optical lens, a mirror, a beam splitter, a microscope objective, and a spectrometer. The low-temperature sample cavity complex system includes a liquid nitrogen Dewar, a gas pressure driven flow device, a three-axis displacement table, a low-temperature sample cavity, a temperature controller, and a pinhole molecular pump. The optical response signal acquisition module includes a fiber spectrometer and a focusing assembly. The sample real-time monitoring and observation system is composed of a CCD camera and a monitor.

[0091] Firstly, the entire spectral response measurement system is as follows:

[0092] Module 1 is a spatial optical path. The broadband light signal generated by the broadband light source is first transmitted through the optical fiber, then shaped by the optical pinhole, and then collimated by the optical lens to form a high-quality parallel light beam. This parallel light beam is accurately guided by the mirrors M1 and M2 and transmitted to the beam splitter BS-1, where it is split. In the split optical path, one beam is focused on the sample surface by the microscope objective, and the other beam is used as a reference light for calibration. The reflected light beam from the sample surface is collimated by the microscope objective and then passes through the second beam splitter BS-2. Part of the light is directed to the CCD camera connected to the monitor to realize real-time monitoring of the sample surface, and the other part is accurately reflected by the mirrors M3 and M4 and then enters the spectrometer for real-time spectral analysis. In addition, this optical path configuration ensures the accurate alignment of the incident light and the reflected light, so that the high-precision spectral response measurement based on the original design can be completed.

[0093] Module 2 is a low-temperature sample cavity system. In order to ensure the stability and controllability of the measurement environment under low-temperature conditions, the system is equipped with a reasonable system architecture. The liquid nitrogen Dewar is used as the main refrigeration source, and is combined with the self-made gas pressure driven flow device, the programmable temperature controller, and the sample heating stage in the sample cavity to realize accurate temperature regulation; the three-axis displacement table ensures micron-level accurate positioning of the sample position; the molecular pump system maintains a high vacuum environment in the sample cavity, and the self-made molecular pump shock absorber can effectively isolate external interference factors.

[0094] Module 3 is a real-time monitoring and observation system, consisting of a CCD camera and a monitor. This system integrates optical microscopy imaging with real-time measurement of optical response. Through the CCD camera and monitor system, operators can observe and precisely locate the two-dimensional planar position of the measurement spot on the sample surface in real time. Simultaneously, the high-performance spectrometer configuration enables the system to perform spectral analysis over a wide wavelength range. This integrated design not only significantly improves the accuracy and repeatability of measurements but also provides the system with the flexibility to adapt to diverse sample measurement needs. Particularly in temperature-dependent studies, the equipped low-temperature sample chamber system greatly expands the experimental exploration range, providing a reliable experimental platform for studying the evolution of the optical properties of two-dimensional materials under different temperature conditions.

[0095] Secondly, the optical response measurement principle of this system is as follows: The system uses the silver mirror reflection method to measure sample reflectivity. This method has self-calibration characteristics, effectively eliminating system errors. The entire optical path design fully considers the requirements of beam quality and measurement accuracy. The parameter selection and spatial layout of optical components have been optimized to minimize the influence of stray light. In the specific implementation of the silver mirror reflectivity measurement, the system adopts a standard comparison measurement scheme. The specific process is as follows: First, a standard silver mirror is placed at the sample position to measure the reflectance spectrum and obtain the reference spectrum I0(λ); then, the sample to be tested is replaced in the same position for measurement to obtain the sample reflectance spectrum I(λ). Based on the known absolute reflectance R0(λ) of the standard silver mirror, the absolute reflectance of the sample can be obtained through ratio calculation: R(λ)=R0(λ)×[I(λ) / I0(λ)]. The design of this system fully meets the actual testing requirements of this invention.

[0096] The temperature-dependent reflectance spectrum of the composite resonant cavity structure (Si / SiO2 / Ag / ITO / WS2 / h-BN / Ag) obtained in this invention is shown in the figure. Figure 6 . Figure 6 In the diagram, the horizontal axis represents photon energy (unit: eV), the vertical axis represents reflectance, and the color gradient represents the ambient temperature at which the device is being tested. Figure 6 In the diagram, C1 / C2 / C3 represent the thicknesses of the h-BN dielectric layer as 30 / 40 / 55 nm, respectively, and are marked with orange / blue / red colors in that order.

[0097] The experimental observations of the Fano resonance in the temperature-tuned reflectance spectrum of this example and its theoretical fitting are shown in [link to example]. Figure 7 The region is 40nm h-BN(C2, in Figure 9 (Represented by a blue closed line). Figure 7Fig. 1 shows the experimental results of the present application, (a) is the fitting curve of the experimental measured reflection spectrum of the device structure with temperature variation and Fano theory, (b) is a three-dimensional schematic diagram of the resonant cavity structure, (c) is the temperature dependence curve of the Fano quality factor q, (d) is the temperature dependence curve of the Fano resonance center wavelength E0, (e) is the temperature dependence curve of the Fano resonance line width Γ. The quality factor represents the sharpness, that is, the larger the Fano line type is, the sharper the spectrum intensity represents the size of the normalized reflection spectrum.

[0098] Fig. 2 shows the model diagram of the exciton absorption in the WS2 atomic layer coupled MDM cavity. Figure 8 . Figure 8 In Fig. 3, C1 / C2 / C3 respectively represent the thickness of the dielectric layer h-BN layer is 30 / 40 / 55nm, and the color of the mark is orange / blue / red in turn.

[0099] Fig. 4 shows the optical micrograph of the composite resonant cavity structure of the present application. Figure 9 . Figure 9 In Fig. 4, (a) is a structural schematic diagram of the Si / SiO2 / Ag / ITO / WS2 / h-BN / Ag multilayer nanometer resonant device and test principle; (b) is the optical micrograph of the Si / SiO2 / Ag / ITO / 3L-WS2 / h-BN / Ag multilayer nanometer resonant device of the present application, and the closed curves of different colors represent four different thicknesses of the h-BN layer, which are marked as C1 / C2 / C3 / C4, and the thicknesses are 30nm / 40nm / 55nm / 0nm in turn, and the colors of the closed curves are orange / blue / red / green in turn.

[0100] Fig. 5 shows the simulation experiment and theoretical fitting of the Fano resonance multi-field tuning characteristics generated by the composite resonant cavity structure of the present application. Figure 10 . Figure 10 In Fig. 6, (a) is the Y-axis offset simulation reflection spectrum of the Si / SiO2 / Ag / ITO / WS2 / h-BN / Ag structure, (b) is the thickness-dependent reflection spectrum of the dielectric layer (h-BN) of the MDM cavity coupled with a single layer of WS2, (c) is the temperature-thickness-dependent reflection spectrum of the MDM cavity coupled with a single layer of WS2, (d) (e) (f) are respectively the temperature-dependent Fano resonance parameter curves extracted by theoretical fitting, and the ordinate is the resonance line width Γ, the resonance energy center wavelength E0 and the resonance quality factor q in turn.

[0101] In the optical nanometer resonator, the coupling of photons and excitons is concerned due to its innovative application potential in spectrum control. The present application designs an optical resonator, which integrates atomically thin tungsten disulfide (WS2) in a metal-dielectric-metal (MDM) nanometer cavity, aiming at manipulating the Fano resonance in photonics.

[0102] Therefore, in combination with Figure 6 , Figure 7 andFigure 10 Data and references Figure 8 , Figure 9 The diagram is analyzed as follows:

[0103] This example demonstrates the effectiveness of a temperature-dependent reflection spectrum obtained through a self-designed micro / nano-scale low-temperature reflectance spectrometer. This observation confirms the theoretical performance of the composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides, as described in this invention. The experimentally measured spectra exhibit the asymmetric spectral response characteristic of the Fano resonance line. Figure 6 Both experimental and numerical simulations confirmed the tunability of these tunable asymmetric Fano resonance spectra, consistent with theoretical predictions. Furthermore, experiments also showed that the resonant wavelength and quality factor (q-factor) of the composite resonant cavity structure of the present invention, based on Fano resonance and coupled with two-dimensional transition metal sulfides, can be tuned by temperature or the thickness of the MDM cavity dielectric layer. Figure 6 , Figure 7 Multiphysics spectral simulations of two-dimensional atomic-layer TMDs coupled to MDM cavities under different conditions also demonstrated the stretching properties of this structure. Figure 10 ).

[0104] To analyze the formation mechanism of the Fano resonance in this structure, a theoretical model of a multilayer electromagnetic medium transport matrix was constructed. Theoretical analysis shows that the Fano resonance originates from the coupling between resonant photons in the nanoresonator and excitons in the WS2 layer.

[0105] In summary, the innovation and reliability of the composite resonant cavity structure of the MDM nanocavity coupled with two-dimensional transition metal sulfides based on Fano resonance in this invention have been fully verified by systematic experiments: using a micro-nano-scale low-temperature reflectance spectroscopy measurement system, a Fano linear reflectance spectrum with significant temperature dependence characteristics was obtained, and for the first time, the tunable asymmetric response characteristics of the Fano resonance in the reflectance spectrum were experimentally confirmed. This invention opens up new technical pathways for atomic-level spectral manipulation and exciton-induced Fano resonance modulation, and has significant scientific and application value.

[0106] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides using MDM nanocavities, characterized in that, The composite resonant cavity structure comprises, in sequence, a metal layer a, a hexagonal boron nitride layer, a tungsten disulfide layer, an indium tin oxide layer, and a metal layer b; The material of the hexagonal boron nitride layer includes hexagonal boron nitride; the material of the indium tin oxide layer includes indium tin oxide; the material of the tungsten disulfide layer includes tungsten disulfide; the material of metal layer a includes one or more of silver, titanium, chromium, and gold; the material of metal layer b includes one or more of silver, titanium, chromium, and gold.

2. The composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 1, characterized in that, The metal layer a is silver layer a, and the metal layer b is silver layer b; the materials of both the silver layer a and the silver layer b include silver.

3. The composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 2, characterized in that, The thickness of the silver layer a is 5-15 nm, the thickness of the hexagonal boron nitride layer is 25-75 nm, the thickness of the tungsten disulfide layer is 0.7-10 nm, the thickness of the indium tin oxide layer is 8-20 nm, and the thickness of the silver layer b is 20-50 nm.

4. The composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 2, characterized in that, The composite resonant cavity structure further includes a silicon wafer substrate; the silicon wafer substrate includes a SiO2 layer attached to one side of the Si layer; the silicon wafer substrate has the SiO2 layer attached to the outer side of the silver layer b.

5. A method for preparing a composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 2, characterized in that, Includes the following steps: S1. The silver layer b is grown using a vacuum evaporation deposition method; S2. The indium tin oxide layer is grown on the surface of the silver layer b using magnetron sputtering deposition. S3. Prepare the tungsten disulfide layer on the surface of the indium tin oxide layer using a mechanical stripping method; S4. Prepare the hexagonal boron nitride layer on the surface of the tungsten disulfide layer using a mechanical stripping method; S5. The silver layer a is grown on the surface of the hexagonal boron nitride layer by vacuum evaporation deposition to obtain the composite resonant cavity structure.

6. The method for preparing the composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 5, characterized in that, Step S3 includes the following steps: S3-1. Prepare two-dimensional tungsten disulfide sheets on the surface of PDMS film. S3-2. Transfer the two-dimensional tungsten disulfide sheet to the surface of the indium tin oxide layer to obtain the tungsten disulfide layer; Step S4 includes the following steps: S4-1. Two-dimensional hexagonal boron nitride sheets are prepared on the surface of PDMS thin film. S4-2. Transfer the two-dimensional hexagonal boron nitride sheet to the surface of the tungsten disulfide layer to obtain the hexagonal boron nitride layer.

7. The method for preparing the composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 6, characterized in that, Step S3-1 specifically involves: placing the tungsten disulfide block onto the adhesive material, repeatedly adhering and peeling it off to obtain a tungsten disulfide layered sheet; then attaching the tungsten disulfide layered sheet onto the PDMS film, peeling off the adhesive material to obtain a two-dimensional tungsten disulfide sheet; Step S3-2 specifically involves: attaching the PDMS film to the surface of the indium tin oxide layer, so that the two-dimensional tungsten disulfide sheet is attached to the indium tin oxide layer; heating the entire structure when the PDMS film is completely attached to the surface of the indium tin oxide layer; and then peeling off the PDMS film to obtain the tungsten disulfide layer. Step S4-1 specifically involves: placing the hexagonal boron nitride block on an adhesive material, repeatedly adhering and peeling it off to obtain a hexagonal boron nitride layered sheet; then attaching the hexagonal boron nitride layered sheet to a PDMS film, peeling off the adhesive material to obtain a two-dimensional hexagonal boron nitride sheet; Step S4-2 specifically involves: attaching the PDMS film to the surface of the tungsten disulfide layer, so that the two-dimensional hexagonal boron nitride sheet is attached to the tungsten disulfide layer; heating the entire structure when the PDMS film is completely attached to the surface of the tungsten disulfide layer; and then peeling off the PDMS film to obtain the hexagonal boron nitride layer.

8. The method for fabricating a composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 5, characterized in that, In step S1, the growth equipment is a vacuum evaporation coating equipment; in step S5, the growth equipment is a vacuum evaporation coating equipment; in step S1, the growth rate is less than 0.5 nm / s, and the growth vacuum degree is less than 10. -5 Pa; In step S5, the growth rate is less than 0.5 nm / s, and the growth vacuum degree is less than 10. -5 Pa; In step S2, the growth equipment is a magnetron sputtering coating equipment; In step S2, the growth conditions include: a pure argon atmosphere and a vacuum degree of less than 10. -4 The sputtering conditions are: Pa, temperature 295℃, sputtering voltage 40V, and target material is indium tin oxide; the purity of the target material is 99.99%; the doping ratio of the target material is In2O3:SnO2 = 9:

1.

9. The method for preparing the composite resonant cavity structure based on Fano resonance and coupled with two-dimensional transition metal sulfides according to claim 5, characterized in that, In step S1, the silver layer b is grown on a silicon wafer substrate; the silicon wafer substrate includes a SiO2 layer attached to one side of the Si layer; the silicon wafer substrate is attached to the outer side of the silver layer b by the SiO2 layer; the thickness of the SiO2 layer includes 250-350 nm; before step S1, the silicon wafer substrate is surface cleaned.

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