Non-linear optical switch based on low-temperature phase variation structure and preparation method of non-linear optical switch

Abstract

The invention discloses a nonlinear optical switch based on a low-temperature phase change material structure and a preparation method thereof, the device comprises a two-dimensional multilayer semiconductor, a vanadium dioxide phase change film and a substrate, and the vanadium dioxide phase change film has a low-temperature insulator-metal reversible phase change characteristic. The two-dimensional multi-layer semiconductor has intrinsic or artificially designed reversal symmetry breaking characteristics. According to the nonlinear optical switch based on the low-temperature phase change mass structure, dynamic regulation and control of nonlinear optical response of a two-dimensional multi-layer semiconductor are achieved through low-temperature phase change of the vanadium dioxide thin film, reversible nonlinear optical switch characteristics are presented, and meanwhile, a universal physical model with interface light field superposition is constructed; the nonlinear optical signal intensity and the switching ratio of the low-temperature phase variation structure of the two-dimensional multilayer semiconductor / VO2 in a metal state and an insulation state are quantitatively calculated by comprehensively considering nonlinear optical field generation of each layer in the two-dimensional multilayer semiconductor, propagation and corner superposition between layers and multiple reflection and interference effects; and the specific structure parameter design of the low-temperature phase-change variable-mass-structure nonlinear optical switch with high switching ratio and wide spectrum response is realized.

Description

Technical Field

[0001] The invention relates to the technical field of nonlinear optical switch devices, and in particular to a nonlinear optical switch based on a low-temperature phase-shifting structure and a preparation method thereof. Background Art

[0002] Nonlinear optical switches are at the core of all-optical computing and all-optical communications. Facing the dual challenges of miniaturization and integration of micro-nano devices, the development of nonlinear optical switches that are easy to integrate on-chip and super-compact has become an urgent problem to be solved. Two-dimensional multilayer semiconductors have extremely large second-order nonlinear polarizability and no dangling bonds between layers, making them very easy to integrate on-chip, and are expected to achieve breakthroughs in the field of on-chip nonlinear optical switches. Existing research focuses on improving the nonlinear conversion efficiency of two-dimensional multilayer semiconductors, while the dynamic regulation of their second-order nonlinearity and even the design of optical switches have not yet been carried out. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a nonlinear optical switch based on a low-temperature phase change heterostructure and a preparation method thereof, and to realize a nonlinear optical switch regulated by a low-temperature phase change by constructing a two-dimensional multilayer semiconductor / vanadium dioxide heterostructure. In the low-temperature phase change heterostructure, the two-dimensional multilayer semiconductor is used as a response layer to generate nonlinear optical signals, and the vanadium dioxide film is used as a control layer to realize the maximum modulation of the fundamental frequency light field by utilizing its low-temperature insulator-metal phase change, thereby presenting a reversible nonlinear optical switch characteristic.

[0004] Technical solution: To achieve the above-mentioned purpose, the nonlinear optical switch based on a low-temperature phase heterostructure described in the present invention includes, from top to bottom, a two-dimensional multilayer semiconductor, a vanadium dioxide thin film, and a substrate. The two-dimensional multilayer semiconductor is a natural multilayer or artificially stacked van der Waals heterojunction, and each layer has an intrinsic or artificially designed inversion symmetry breaking characteristic. The nonlinear optical signal intensity of the two-dimensional multilayer semiconductor exhibits coherent enhancement as the thickness of the two-dimensional multilayer semiconductor increases.

[0005] The substrate material includes a transparent substrate and a non-transparent substrate, wherein the transparent substrate includes sapphire Al2O3, and the non-transparent substrate includes silicon dioxide SiO2.

[0006] Among them, the two-dimensional multilayer semiconductor is a III-VI compound with broken intrinsic inversion symmetry, including indium selenide InSe, gallium selenide GaSe, or 3R phase transition metal chalcogenide, including 3R-MoS2, or rhombohedral boron nitride rBN, or artificially stacked corner van der Waals heterojunction.

[0007] The wavelength corresponding to the band gap of the two-dimensional multilayer semiconductor is smaller than the central wavelength of the fundamental frequency light of the nonlinear effect, and the two-dimensional multilayer semiconductor has a high nonlinear polarizability at the wavelength of the fundamental frequency light.

[0008] Among them, a physical model of interface light field superposition was constructed, and the nonlinear optical signal intensity and switching ratio of the nonlinear optical switch regulated by low-temperature phase change were quantitatively calculated.

[0009] The calculation formula of the superposition electric field strength of the nonlinear optical signal is:

[0010]

[0011] Among them, air is medium 0, two-dimensional multilayer semiconductor is medium 1, vanadium dioxide film is medium 2, R ij and T ij are the reflection coefficient and transmission coefficient of the nonlinear frequency-doubled optical signal incident from medium i to medium j; r ij and t ij is the reflection coefficient and transmission coefficient of the nonlinear fundamental frequency optical signal incident from medium i to medium j; l is the number of layers of the two-dimensional multilayer semiconductor; d1 is the thickness of a single layer in the two-dimensional multilayer semiconductor, is the propagation phase delay and rotation phase delay of the nonlinear frequency-doubled optical signal of a single layer. For intrinsic natural multilayers, Φ1 = 0; It is the phase delay caused by the thickness d1 of a layer of fundamental frequency light propagating; this formula can fully describe the relationship between the superposition electric field intensity of nonlinear optical signals and the wavelength of fundamental frequency light and the thickness of two-dimensional semiconductor.

[0012] Wherein, the switch ratio calculation formula is:

[0013]

[0014] Among them, the denominator represents the intensity of the nonlinear frequency-doubled light signal in the insulating state before the phase transition of the vanadium dioxide film, and the numerator represents the intensity of the nonlinear frequency-doubled light signal in the metallic state after the phase transition of the vanadium dioxide film. This formula can fully describe the relationship between the switching ratio of the nonlinear optical switch and the wavelength of the fundamental frequency light and the thickness of the two-dimensional semiconductor.

[0015] The present invention provides a method for preparing a nonlinear optical switch based on a low-temperature phase heteromorphic structure, comprising:

[0016] (1) A vanadium dioxide film is prepared on a substrate, and the wavelength modulation range of the low-temperature phase transition is obtained by temperature-dependent transmission spectrum testing;

[0017] (2) Using the physical model of the interface optical field superposition, the optimal thickness of the two-dimensional multilayer semiconductor layer required for a nonlinear optical switch based on a low-temperature phase heterostructure with a high switching ratio at a specific wavelength is calculated.

[0018] (3) Prepare two-dimensional multilayer semiconductors by mechanical exfoliation or chemical vapor deposition, or prepare corner-stacked van der Waals heterojunctions using micro-nano transfer to obtain two-dimensional multilayer semiconductors with broken inversion symmetry; obtain band gap information of the two-dimensional multilayer semiconductor by measuring the photoluminescence spectrum or absorption spectrum of the two-dimensional multilayer semiconductor to determine the applicable fundamental frequency wavelength range; obtain thickness information of the two-dimensional multilayer semiconductor by using a step profiler or atomic force microscope to determine that the prepared sample has an optimal thickness;

[0019] (4) Using a micro-nano transfer platform, the two-dimensional multilayer semiconductor with the optimal thickness in the prepared sample is aligned and transferred to the vanadium dioxide film to construct a nonlinear optical switch of the two-dimensional multilayer semiconductor / vanadium dioxide film / substrate.

[0020] Beneficial effects: The present invention has the following advantages: 1. The nonlinear optical switch based on the low-temperature phase heteromorphic structure of the present invention realizes the dynamic regulation of the nonlinear optical response of the two-dimensional multilayer semiconductor through the low-temperature phase change of the vanadium dioxide film, and based on the proposed physical model, presents a nonlinear optical switch characteristic with a high switching ratio;

[0021] 2. The present invention constructs a universal physical model of interface light field superposition, comprehensively considers the nonlinear light field generation of each layer in the two-dimensional multilayer semiconductor, the propagation and angle superposition between layers, and multiple reflection and interference effects, and quantitatively calculates the nonlinear light signal intensity and switching ratio of the low-temperature heterophase heterostructure of the two-dimensional multilayer semiconductor layer / VO2 in the metallic state and the insulating state, thereby realizing the specific structural parameter design of the nonlinear optical switch of the low-temperature heterophase heterostructure with high switching ratio and wide spectrum response;

[0022] 3. The nonlinear optical switch based on low-temperature phase heterostructure provides a new approach for the development of on-chip frequency conversion devices and optical modulation devices based on two-dimensional layered semiconductors. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a hierarchical structure of a nonlinear optical switch based on a low-temperature phase heteromorphic structure;

[0024] Figure 2 (a) is the temperature-dependent resistance hysteresis curve of the vanadium dioxide film, and (b) is the wavelength-dependent optical transmittance spectrum of the vanadium dioxide film in the insulating state and the metallic state;

[0025] Figure 3 (a)(b) are the switching test diagrams of the nonlinear second harmonic signal of the two-dimensional multilayer semiconductor / vanadium dioxide heterostructure during the heating and cooling process;

[0026] Figure 4(a)(b) are the physical model schematic diagram and light field superposition diagram of the interface light field superposition of the two-dimensional multilayer semiconductor / insulating vanadium dioxide heterostructure; Figure 4 (c)(d) Schematic diagram of the physical model and light field superposition diagram of the interface light field superposition of a two-dimensional multilayer semiconductor / metallic vanadium dioxide heterostructure;

[0027] Figure 5 (a) Thickness dependence of the nonlinear optical signal intensity of a two-dimensional multilayer semiconductor based on the interface light field superposition physics model; Figure 5 (b) Thickness dependence of the switching ratio of a two-dimensional multilayer semiconductor nonlinear optical switch based on the interface light field superposition physics model. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below in conjunction with the embodiments and drawings.

[0029] like Figure 1 As shown, the present invention uses aluminum oxide (Al2O3) as a substrate to provide a method for preparing a nonlinear optical switch of an indium selenide (InSe) / vanadium dioxide (VO2) heterostructure, comprising:

[0030] (1) A vanadium dioxide film with a thickness of 25 nm was prepared on a substrate by magnetron sputtering, chemical vapor deposition or molecular beam epitaxy, and the wavelength modulation range of the low-temperature phase transition was obtained by variable temperature transmission spectrum testing.

[0031] like Figure 2 Shown are the temperature-dependent resistance hysteresis curve of the vanadium dioxide film and the wavelength-dependent optical transmittance spectra of the vanadium dioxide film in the insulating state and the metallic state. Figure 2 In (a), the resistance of the vanadium dioxide film changes with temperature during heating and cooling, indicating that vanadium dioxide undergoes a sharp transition from the insulating state to the metallic state (IMT). Figure 2 In (b), the transmission spectra of the vanadium dioxide film in the insulating state (black solid line) and the metallic state (black solid line) are almost the same in the visible light band, but show great differences in the infrared wavelength region, where the transmittance of the vanadium dioxide film in the metallic state is greatly reduced.

[0032] (2) Use a mechanical stripping method to peel off multiple layers of InSe from the InSe material; obtain its band gap information by measuring the photoluminescence spectrum or absorption spectrum of the multilayer InSe to determine the applicable fundamental frequency wavelength range; use a step profiler or atomic force microscope to obtain the thickness information of the multilayer InSe;

[0033] (3) Using a micro-nano transfer platform, the prepared multilayer InSe is aligned and transferred to the vanadium dioxide film to construct a nonlinear optical switch of multilayer InSe / VO2 film / Al2O3 substrate.

[0034] Furthermore, the switching of the nonlinear second harmonic signal of the prepared nonlinear optical switch during the heating and cooling process was tested, such as Figure 3 The test conditions include: selecting a fixed fundamental power of 6.6mW, heating and cooling the vanadium dioxide film to the insulating state (40℃, 55℃), the transition from the insulating state to the metallic state (64℃, 68℃ and 72℃), and the metallic state (80℃, 90℃ and 100℃). Figure 3 (a) is the heating process. When the vanadium dioxide film is in the insulating state, the second harmonic signal of the nonlinear optical switch is weak. When the vanadium dioxide film changes from the insulating state to the metallic state, the second harmonic signal jumps and maintains a high second harmonic signal. Figure 3 (b) is the cooling process. When the vanadium dioxide film is in the metallic state and when it changes from the insulating state to the metallic state, the nonlinear optical switch maintains a high second harmonic signal. In the insulating state, the second harmonic signal is weak.

[0035] The test results show that the nonlinear optical switch based on the low-temperature phase heteromorphic structure can dynamically control the nonlinear optical response of two-dimensional multilayer semiconductors through the low-temperature phase transition of vanadium dioxide thin films, and presents reversible nonlinear optical switching characteristics. The experimentally measured switching ratio of the nonlinear optical switch is 4 (the average value of the second harmonic signal intensity maintained higher divided by the average value of the second harmonic signal intensity weaker in the figure).

[0036] Furthermore, an interface optical field superposition model of a multilayer InSe / vanadium dioxide heterostructure is constructed. The physical model of the interface optical field superposition can quantitatively calculate the nonlinear optical signal intensity and the switching ratio of the nonlinear optical switch regulated by the low-temperature phase change, and fully describes the relationship between the superposition electric field intensity of the nonlinear optical signal and the wavelength of the fundamental frequency light and the thickness of the two-dimensional semiconductor, as well as the relationship between the switching ratio of the nonlinear optical switch and the wavelength of the fundamental frequency light and the thickness of the two-dimensional semiconductor. Figure 4 As shown, Figure 4 (a)(b) are the physical model schematic diagram and light field superposition diagram of the interface light field superposition of multilayer InSe / insulating vanadium dioxide heterostructure; Figure 4 (c)(d) Schematic diagram of the physical model of the interface light field superposition of the multilayer InSe / metallic vanadium dioxide heterostructure and the light field superposition diagram. It can be seen from the figure that compared with the insulating state, the second harmonic signal of the multilayer InSe / vanadium dioxide heterostructure is significantly enhanced in the metallic state of vanadium dioxide. At the Air-MLs and MLs-VO2 interfaces, both the fundamental frequency light and the doubled frequency light signals are reflected and transmitted (the red arrow indicates the electric field of the fundamental frequency light ω, the green arrow indicates the second harmonic signal caused by the incident fundamental frequency light, and the blue arrow indicates the second harmonic signal caused by the reflected fundamental frequency light).

[0037] Furthermore, the interface light field superposition physical model is used to calculate the thickness dependence of the two-dimensional multilayer semiconductor nonlinear optical signal intensity and the thickness dependence of the two-dimensional multilayer semiconductor nonlinear optical switch ratio. The calculation results are as follows: Figure 5 shown.

[0038] Among them, the calculation formula for the superposition electric field strength of nonlinear optical signals is:

[0039]

[0040] In the formula, air is medium 0, two-dimensional multilayer semiconductor is medium 1, vanadium dioxide film is medium 2, R ij and T ij are the reflection coefficient and transmission coefficient of the nonlinear frequency-doubled optical signal incident from medium i to medium j; r ij and t ij is the reflection coefficient and transmission coefficient of the nonlinear fundamental frequency optical signal incident from medium i to medium j; l is the number of layers of the two-dimensional multilayer semiconductor; d1 is the thickness of a single layer in the two-dimensional multilayer semiconductor, is the propagation phase delay and rotation phase delay of the nonlinear frequency-doubled optical signal of a single layer, and for intrinsic natural multilayers, φ1 = 0; It is the phase delay caused by the fundamental frequency light propagating through a layer of thickness d1.

[0041] The on / off ratio is calculated as:

[0042]

[0043] Wherein, the denominator represents the intensity of the nonlinear frequency-doubled optical signal in the insulating state before the phase transition of the vanadium dioxide film, and the numerator represents the intensity of the nonlinear frequency-doubled optical signal in the metallic state after the phase transition of the vanadium dioxide film.

[0044] in, Figure 5 (a) is the second harmonic signal intensity of multilayer InSe calculated by the interface light field superposition model under different multilayer InSe thicknesses (the thickness of the multilayer InSe ranges from 10nm to 1000nm, with an interval of 2nm, and the inset is a local enlarged view of the area <100nm). It can be seen that when vanadium dioxide is in the metallic state, the second harmonic signal of multilayer InSe is significantly enhanced. Figure 5 (b) The switching ratio of multilayer InSe calculated by the interface light field superposition model shows a fluctuating oscillation as the sample thickness changes, which may be related to multiple reflections and interference effects in light propagation; in the shaded area of ​​the figure, the SHG switching ratio of multilayer InSe is about 5, which is very close to the results measured by the experiment above.

[0045] The results show that the physical model of interface light field superposition constructed by the present invention comprehensively considers the nonlinear light field generation of each layer in the two-dimensional multilayer semiconductor, the propagation and angle superposition between layers, and multiple reflection and interference effects, etc., and can quantitatively calculate the nonlinear light signal intensity and switching ratio of the low-temperature phase heterostructure of the two-dimensional multilayer semiconductor layer / VO2 in the metallic state and the insulating state, and realize the specific structural parameter design of the low-temperature phase heterostructure nonlinear optical switch with high switching ratio and wide spectrum response.

[0046] The present invention further provides a physical model of the interface light field superposition and a working principle of the interface light field superposition model, which is specifically described as follows:

[0047] When the nonlinear optical switch is illuminated by an ultrafast laser with fundamental frequency light ω, the two-dimensional multilayer semiconductor will generate second harmonic photons with doubled frequency 2ω in the same direction as the fundamental frequency light, and the second harmonic electric field is expressed as:

[0048]

[0049] where χ (2) is the second-order polarizability, E ω is the electric field of the fundamental frequency light.

[0050] Since the inversion symmetry of two-dimensional multilayer semiconductors is always broken, there will be a phase-delayed second harmonic signal between each layer. In addition, the two-dimensional multilayer semiconductor is located on the vanadium dioxide film to form a three-medium (Air, MLs (such as multilayer InSe) and VO2) structure, in which the refractive index at the Air-MLs and MLs-VO2 interfaces is different, and the multiple reflection and interference effects of ω and 2ω should be considered at the same time.

[0051] Due to the low frequency doubling conversion efficiency, the fundamental frequency light amplitude E of each layer in the two-dimensional multilayer semiconductor is ω Basically, it remains constant. For the incidence of fundamental frequency light, the first layer starting from the top generates a second harmonic electric field. The second layer generates a second harmonic electric field When the number of layers is l, the corresponding second harmonic electric field is

[0052] When the distance between the two-dimensional multilayer semiconductor layers is d1, the superposition of these second harmonic electric fields will cause an additional phase delay of Φ. These second harmonic electric fields are reflected multiple times in the Air-MLs-VO2 structure, and considering the interference effect, the first superposition total electric field caused by the fundamental frequency light incident can be obtained. It can be expressed as:

[0053]

[0054] The reflected fundamental frequency light at the InSe-VO2 interface interacts with the two-dimensional multilayer semiconductor again, thereby generating another sequence of second harmonic signals, whose electric fields are as follows from bottom to top: and There is a phase delay between each layer. These electric fields are affected by multiple reflections and interference effects at the interface. The first superposition total electric field caused by the reflection of the fundamental frequency light It can be expressed as:

[0055]

[0056] Since the fundamental frequency light also has multiple reflections in the Air-MLs-VO2 structure, the fundamental frequency light signal reflected at the Air-MLs interface will repeat the above two processes and induce the electric field caused by the fundamental frequency light incident. and the electric field caused by the reflection of the fundamental frequency light Superposition state of all second harmonic electric fields It can be given by the following formula. It can be seen that the electric field strength is completely determined by the complex refractive index.

[0057]

[0058] When the nonlinear optical switch sample is heated, the VO2 insulating-metallic transition (IMT) causes a specific change in the complex refractive index of the two-dimensional multilayer semiconductor, which leads to an increase in the reflectivity of the fundamental and doubled frequency light at the MLs-VO2 interface, thereby increasing and The amplitude of the oscillation is finally realized through the insulating-metallic transition of VO2 to realize the switching of the second harmonic response of the two-dimensional multilayer semiconductor.

Claims

1. A nonlinear optical switch based on a low-temperature phase-variant structure, characterized in that: From top to bottom, it includes a two-dimensional multilayer semiconductor, a vanadium dioxide thin film, and a substrate. The two-dimensional multilayer semiconductor is a natural multilayer or artificially stacked van der Waals heterojunction, and each layer has an intrinsic or artificially designed inversion symmetry breaking characteristic. The nonlinear optical signal intensity of the two-dimensional multilayer semiconductor exhibits coherent enhancement as the thickness of the two-dimensional multilayer semiconductor increases.

2. The nonlinear optical switch of the low-temperature phase heterogeneous structure according to claim 1, characterized in that: The substrate material includes a transparent substrate and a non-transparent substrate, wherein the transparent substrate includes sapphire Al2O3, and the non-transparent substrate includes silicon dioxide SiO2.

3. The nonlinear optical switch based on low temperature phase heterogeneous structure according to claim 1, characterized in that: The two-dimensional multilayer semiconductor is a III-VI compound with broken intrinsic inversion symmetry, including indium selenide InSe, gallium selenide GaSe, or 3R phase transition metal chalcogenide, including 3R-MoS2, or rhombohedral boron nitride rBN, or an artificially stacked corner van der Waals heterojunction.

4. The nonlinear optical switch based on low temperature phase heterogeneous structure according to claim 1, characterized in that: The wavelength corresponding to the band gap of the two-dimensional multilayer semiconductor is smaller than the central wavelength of the fundamental frequency light of the nonlinear effect, and the two-dimensional multilayer semiconductor has a high nonlinear polarizability at the wavelength of the fundamental frequency light.

5. The nonlinear optical switch based on low temperature phase heterogeneous structure according to claim 1, characterized in that: A physical model of interface light field superposition was constructed, and the nonlinear optical signal intensity and switching ratio of the nonlinear optical switch regulated by low-temperature phase change were quantitatively calculated.

6. The nonlinear optical switch based on low-temperature phase heterostructure according to claim 5, characterized in that: The calculation formula of the superposition electric field strength of the nonlinear optical signal is: In the example, air is medium 0, two-dimensional multilayer semiconductor is medium 1, vanadium dioxide film is medium 2, R ij and T ij are the reflection coefficient and transmission coefficient of the nonlinear frequency-doubled optical signal incident from medium i to medium j; r ij and t ij is the reflection coefficient and transmission coefficient of the nonlinear fundamental frequency optical signal incident from medium i to medium j; l is the number of layers of the two-dimensional multilayer semiconductor; d1 is the thickness of a single layer in the two-dimensional multilayer semiconductor, is the propagation phase delay and rotation phase delay of the nonlinear frequency-doubled optical signal of a single layer. For the intrinsic natural multilayer It is the phase delay caused by the fundamental frequency light propagating through a layer of thickness d1; The superposition electric field intensity calculation formula of the nonlinear optical signal can establish the relationship between the superposition electric field intensity of the nonlinear optical signal and the wavelength of the fundamental frequency light and the thickness of the two-dimensional multilayer semiconductor.

7. The nonlinear optical switch based on low-temperature phase heterostructure according to claim 5, characterized in that: The switch ratio calculation formula is: The denominator represents the intensity of the nonlinear frequency-doubled optical signal in the insulating state before the phase transition of the vanadium dioxide film, and the numerator represents the intensity of the nonlinear frequency-doubled optical signal in the metallic state after the phase transition of the vanadium dioxide film. The switch ratio calculation formula can establish the relationship between the switch ratio of the nonlinear optical switch and the wavelength of the fundamental frequency light and the thickness of the two-dimensional multilayer semiconductor.

8. A method for preparing a nonlinear optical switch based on a low-temperature phase heteromorphic structure as claimed in claim 5, characterized in that: include: (1) A vanadium dioxide film is prepared on a substrate, and the wavelength modulation range of the low-temperature phase transition is obtained by temperature-dependent transmission spectrum testing; (2) Using the physical model of interface optical field superposition, calculate the optimal thickness of two-dimensional multilayer semiconductors required for nonlinear optical switches based on low-temperature phase heterostructures with high switching ratios at specific wavelengths; (3) preparing a two-dimensional multilayer semiconductor by mechanical exfoliation or chemical vapor deposition, or preparing a corner-stacked van der Waals heterojunction by micro-nano transfer, to obtain a two-dimensional multilayer semiconductor with broken inversion symmetry; obtaining band gap information of the two-dimensional multilayer semiconductor by measuring the photoluminescence spectrum or absorption spectrum of the two-dimensional multilayer semiconductor, which is used to determine the applicable fundamental frequency wavelength range; obtaining thickness information of the two-dimensional multilayer semiconductor by using a step profiler or atomic force microscope to determine that the prepared sample has an optimal thickness; (4) Using a micro-nano transfer platform, the two-dimensional multilayer semiconductor with the optimal thickness in the prepared sample is aligned and transferred to the vanadium dioxide film to construct a nonlinear optical switch of the two-dimensional multilayer semiconductor / vanadium dioxide film / substrate.

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