Verification method of thermo-optical control of optical spin Hall effect based on VO2 thin film

Abstract

The present invention discloses a verification method for thermo-optically regulated optical spin Hall effect based on VO2 thin film, which belongs to the field of optical spin Hall effect regulation, and includes the following steps: S1, simulation experiment verification: S11, preparation of VO2 thin film sample; S12, solution of sample reflection coefficient; S13, solution of lateral displacement value of optical spin Hall effect on the surface of VO2 thin film sample before and after phase change; S2, experimental verification: S21, construction of experimental platform; S22, after preheating, setting the center of mass position of the light spot at this time as the initial position; S23, plotting the curve of the center of mass position of the light spot changing with temperature; S3, cross-validation: judging the feasibility of using temperature to regulate the optical spin Hall effect of VO2 thin film. The present invention adopts the above-mentioned verification method for thermo-optically regulated optical spin Hall effect based on VO2 thin film, and cross-validates the thermo-optically regulated optical spin Hall effect through simulation and experiment, which provides a new way to regulate optical properties using thermo-induced phase change materials.

Description

Technical Field

[0001] The present invention relates to the technical field of photo-spin Hall effect regulation, and in particular to a verification method of photo-spin Hall effect regulated by thermo-optical means based on VO2 thin films. Background Art

[0002] With the continuous advancement of science and technology, society's demand for smart materials is increasing. Smart materials have the ability to respond to external stimuli and exhibit special properties, so they have attracted much attention. Among many smart materials, thermochromic materials have attracted extensive research due to their unique properties. These materials can undergo structural or property changes when stimulated by temperature changes, thereby exhibiting different electrical or optical properties. This property makes thermochromic materials have potential application prospects in fields such as smart windows, temperature sensors, and optical switches.

[0003] Vanadium is a multivalent transition metal element that can form a variety of different oxides. Among them, VO2 has a variety of crystal forms, and the crystal forms of VO2 can be transformed into each other under the conditions of electric field, laser, stress and temperature. Morin published a paper in 1959 showing that VO2 will undergo a metal-insulator transition (MIT) after exceeding 68°C, and this change is reversible. VO2 has since received widespread attention. The MIT change time of VO2 is very short, usually within 10-12s, and after VO2 undergoes MIT, not only the crystal structure changes, but also its optical and electrical properties will change dramatically.

[0004] Specifically, when the ambient temperature of VO2 is higher than the critical temperature of phase transition, its crystal structure is tetragonal rutile phase, i.e. R phase. At this time, in an octahedral unit structure, the body center and vertex positions are V 4+ Atom, each V 4+ Atom and 6 surrounding O 2- Ionic bonding, the distance between the nearest adjacent VV atoms is about In this state, all metal V atoms share the d orbital electrons in the V atom, and the conductivity is about 10 -6 Ω·m, showing metallic state.

[0005] When the ambient temperature of VO2 is lower than the critical temperature of phase transition, its crystal structure is monoclinic phase, namely M phase. At this time, the length of the crystal axis of VO2 becomes longer, the V atoms deviate from the vertex position, and the crystal structure changes from a highly symmetric tetragonal structure to a low-symmetry monoclinic structure. Macroscopically, it manifests as a distorted rutile crystal structure, and the unit cell volume of M phase VO2 is twice that of R phase. In this case, the secondary polymerization between V atoms causes VV atoms to form a long and short alternating zigzag structure, and the VV distances between the closest V atoms are respectively and The d-orbital electrons are bound in the dimer, and the resistivity is about 0.1Ω·m, making VO2(M) exhibit insulating properties.

[0006] VO2 has attracted much attention due to its unique thermoinduced phase change properties. Since its phase change temperature is about 68°C, this property allows VO2 to undergo phase change at a relatively low temperature, making it one of the most widely studied thermoinduced phase change materials. It also makes it possible to thermo-optically control the optical spin Hall effect based on VO2 thin films.

[0007] At the same time, as a typical optical phenomenon, the optical spin Hall effect is very sensitive to changes in the optical properties of materials. Thermo-optical optical spin Hall effect uses the thermo-optical effect of materials to change their optical properties such as dielectric constant by changing the temperature, so as to achieve the regulation of the optical spin Hall effect displacement. However, there is currently a lack of research reports on thermo-optical regulation of optical spin Hall effect based on VO2 thin films. Summary of the invention

[0008] To solve the above problems, the present invention provides a verification method for thermo-optical regulation of optical spin Hall effect based on VO2 thin film. The thermo-optical regulation of optical spin Hall effect is cross-verified through simulation and experimental verification, providing a new way to regulate optical properties using thermoinduced phase change materials.

[0009] To achieve the above object, the present invention provides a verification method for thermo-optically regulated optical spin Hall effect based on VO2 thin film, comprising the following steps:

[0010] S1. Simulation experiment verification:

[0011] S11, preparing VO2 thin film samples;

[0012] S12. According to Snell's law, a propagation model of the light beam in the medium is established to solve the reflection coefficient of the VO2 thin film sample;

[0013] S13. Based on the principle of geometric optics, the lateral shift value of the optical spin Hall effect on the surface of the VO2 thin film sample before and after the phase change is solved;

[0014] S2. Experimental verification:

[0015] S21. Build an experimental platform: Arrange He-Ne laser, half-wave plate, short-focus lens, first Glan laser polarizer, VO2 thin film sample, second Glan laser polarizer, long-focus lens, CCD camera in sequence along the direction of light propagation, install a heater at the bottom of the VO2 thin film sample, and connect the CCD camera to the computer;

[0016] S22, after preheating, setting the centroid position of the light spot at this time as the initial position;

[0017] S23. A heating experiment was conducted on the VO2 thin film sample using a heater, and a curve of the change of the center of mass position of the light spot with temperature was plotted, and the movement of the center of mass of the light spot was used as the lateral displacement value of the optical spin Hall effect;

[0018] S3. Cross-validation: Compare the results of step S13 and step S23 to determine the feasibility of using temperature to control the optical spin Hall effect of VO2 thin film.

[0019] Preferably, the VO2 thin film sample described in step S11 includes a VO2 thin film and a sapphire substrate located at the bottom of the VO2 thin film.

[0020] Preferably, step S12 specifically includes the following steps:

[0021] S121. The incident wavelength of the laser beam is set to 633 nm. According to Snell's law, the Fresnel reflection coefficients of the s-wave and p-wave are expressed as:

[0022]

[0023] In the formula, It represents the Fresnel reflection coefficient of s-polarized light at the interface between air and VO2 film; It represents the Fresnel reflection coefficient of p-polarized light at the interface between air and VO2 film; It represents the Fresnel reflection coefficient of s-polarized light at the interface between VO2 film and sapphire substrate; represents the Fresnel reflection coefficient of p-polarized light at the interface between VO2 film and sapphire substrate; n1 represents the refractive index of air; n2 represents the refractive index of VO2 film; n3 represents the refractive index of sapphire substrate; θ j (j=1,2,3) respectively represent the angles of the light beam when it enters different dielectric layers;

[0024] S122. Derivation of the Fresnel reflection coefficient r of s-polarized light of VO2 thin film sample s and the Fresnel reflection coefficient r of p-polarized light p :

[0025]

[0026] In the formula, δ represents the optical path difference caused by the light beam passing through the VO2 film:

[0027]

[0028] Where λ0 represents the free space wavelength and d represents the VO2 film thickness.

[0029] Preferably, in step S13, the lateral displacement δ of the light beam spin component is established by using the principle of geometric optics. wNumerical calculation model of:

[0030]

[0031] Where Δ represents the magnification angle; k0 represents the incident light wave vector; z r represents the Rayleigh distance.

[0032] Preferably, the heater described in step S21 is a heating electrode fixed on a solid prism.

[0033] Preferably, step S22 specifically includes the following steps:

[0034] S221. Before the experiment begins, the VO2 thin film sample is preheated, the heater temperature is adjusted to 30°C, and maintained at this state for 10 minutes, so that the temperature of the VO2 thin film sample is kept at 30°C to maintain a relatively stable state;

[0035] S222, turn on the He-Ne laser light source to emit a 632.8 nm laser beam;

[0036] S223. Adjust the half-wave plate to make the light intensity reach the set requirement, and then adjust the first Glan laser polarizer and the second Glan laser polarizer until two evenly distributed light spots are observed on the computer screen connected to the CCD. When the light spots are evenly distributed, the center of mass of the entire light field is equal to the center of mass of the light spot distribution. The position of the light spot at this time is defined as the initial state, and the lateral shift value of the optical spin Hall effect is set to 0. The movement of the center of mass position is used as the lateral shift value of the optical spin Hall effect. On this basis, a heating experiment is carried out.

[0037] Preferably, step S23 specifically includes the following steps:

[0038] S231, heating at intervals of 10°C, and when the heater shows that it has reached the set temperature, wait for 5 minutes, and measure the surface temperature of the VO2 film sample with a temperature gun, and record the centroid position of the light spot;

[0039] S232. When the surface temperature of the VO2 film sample reaches 60°C, the heating interval can be adjusted to 2°C. Whenever the heater displays that it has reached the set temperature, wait for 5 minutes and measure the surface temperature of the VO2 film sample with a temperature gun, while recording the centroid position of the light spot.

[0040] S233, when the phase transition temperature is reached, continue heating, and record the centroid position of the light spot;

[0041] S234. After reaching the set heating temperature, stop heating to make the VO2 thin film sample, and record the center of mass position of the light spot during the cooling process.

[0042] The present invention has the following beneficial effects:

[0043] 1. The thermo-optical control of optical spin Hall effect was verified through simulation and experiment, providing a new way to control optical properties using thermo-induced phase change materials;

[0044] 2. The optical spin Hall effect is regulated by using the change of the complex refractive index before and after the phase change of the VO2 film. The spin shift of the light beam changes significantly before and after the phase change. At the same time, the spin shift will also change during the temperature change process, effectively realizing the temperature regulation of the optical spin Hall effect;

[0045] 3. The change of light spin transverse shift can be used to characterize the phase change of materials, which can be used as a new type of optical detection method without direct contact and with high sensitivity.

[0046] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flow chart of the verification method of the thermo-optical control of the optical spin Hall effect based on VO2 thin film of the present invention;

[0048] Figure 2 A structural diagram of a VO2 thin film for verifying the thermo-optical control of the optical spin Hall effect based on a VO2 thin film according to the present invention;

[0049] Figure 3 : is a reflection coefficient curve diagram of the VO2 thin film before and after phase change of Example 1 of the present invention; wherein Figure 3 (a) is the reflection coefficient r of VO2 thin film before phase transition s and r p Change curve; Figure 3 (b) is the reflection coefficient r of VO2 thin film after phase change s and r p Change curve;

[0050] Figure 4 1 is the PSHE displacement curve before and after the VO2 phase transition of Example 1 of the present invention;

[0051] Figure 5 This is a structural diagram of an experimental platform according to Embodiment 2 of the present invention;

[0052] Figure 6 is a graph showing the relationship between the beam centroid displacement and temperature according to Example 2 of the present invention;

[0053] Figure 7 This is a diagram of the intensity distribution of split light after being magnified by the experimental platform in Example 2 of the present invention.

[0054] Among them, 1. He-Ne laser; 2. half-wave plate; 3. short-focus lens; 4. first Glan laser polarizer; 5. VO2 thin film sample; 51. VO2 thin film; 52. sapphire substrate; 6. second Glan laser polarizer; 7. long focal length lens; 8. CCD camera. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0056] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0057] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0058] At room temperature, VO2 thin film can be induced to undergo phase change by electric heating, laser heating and other methods. As the temperature rises, the critical temperature of VO2 phase change is gradually reached. After VO2 undergoes phase change, the conductivity changes by several orders of magnitude, from an insulating state to a metallic state. Its optical properties also undergo great changes, which are specifically manifested as a change in the dielectric constant, from high transmittance to high reflectivity. By analyzing its dielectric constant matrix, the change in its complex refractive index can be obtained. And the refractive index gradient is one of the effective methods to regulate the optical spin Hall effect, so it can be foreseen that the phase change of VO2 thin film can effectively regulate the optical spin Hall effect.

[0059] Based on the above analysis, the present invention is designed as follows: Figure 1 and Figure 2 As shown, the verification method of the thermo-optical control of the optical spin Hall effect based on VO2 film includes the following steps:

[0060] S1. Simulation experiment verification:

[0061] S11, preparing VO2 thin film sample 5;

[0062] The VO2 thin film sample 5 described in step S11 includes a VO2 thin film 51 and a sapphire substrate 52 located at the bottom of the VO2 thin film.

[0063] S12. According to Snell's law, a propagation model of the light beam in the medium is established to solve the reflection coefficient of the VO2 thin film sample;

[0064] Step S12 specifically includes the following steps:

[0065] S121. The incident wavelength of the laser beam is set to 633 nm. According to Snell's law, the Fresnel reflection coefficients of the s-wave and p-wave are expressed as:

[0066]

[0067] In the formula, It represents the Fresnel reflection coefficient of s-polarized light at the interface between air and VO2 film; It represents the Fresnel reflection coefficient of p-polarized light at the interface between air and VO2 film; It represents the Fresnel reflection coefficient of s-polarized light at the interface between VO2 film and sapphire substrate; represents the Fresnel reflection coefficient of p-polarized light at the interface between VO2 film and sapphire substrate; n1 represents the refractive index of air; n2 represents the refractive index of VO2 film; n3 represents the refractive index of sapphire substrate; θ j (j=1,2,3) respectively represent the angles of the light beam when it enters different dielectric layers;

[0068] S122. Derived and obtained the Fresnel reflection coefficient r of s-polarized light of VO2 thin film sample 5 s and the Fresnel reflection coefficient r of p-polarized light p :

[0069]

[0070] In the formula, δ represents the optical path difference caused by the light beam passing through the VO2 film:

[0071]

[0072] Where λ0 represents the free space wavelength and d represents the VO2 film thickness.

[0073] 4. The verification method of the thermo-optical control of optical spin Hall effect based on VO2 thin film according to claim 3 is characterized in that: in step S13, the lateral displacement δ of the spin component of the light beam is established by using the principle of geometric optics. w Numerical calculation model of:

[0074]

[0075] Where Δ represents the magnification angle; k0 represents the incident light wave vector; z r represents the Rayleigh distance.

[0076] Example 1

[0077] like Figure 3 As shown, before VO2 undergoes phase transition, r s With r p The difference is small and the change is relatively gentle; until the temperature reaches 68℃, VO2 undergoes phase transition, r s With r p The difference increases significantly. This significant change shows that the reflection characteristics of the VO2 film after phase change for s-polarized light and p-polarized light are significantly different. And from the polarization effect, it can be seen that the optical spin Hall effect shift depends on the difference in the reflection coefficients of s-polarized light and p-polarized light. s With r p When the difference is large, the photo-spin Hall effect is more obvious.

[0078] like Figure 4 As shown in the figure, at an incident angle of θ = 72.7°, before the VO2 phase transition, the optical spin Hall effect exists but is very weak. As the temperature rises to the critical temperature of the phase transition, VO2 changes from an insulating state to a metallic state, and its conductivity and refractive index change significantly, which significantly enhances the optical spin Hall effect and significantly increases the splitting value to 88.1μm, which is about 67μm higher than before the phase transition, realizing the thermo-optical control of the optical spin Hall effect.

[0079] At the same time, from the intensity distribution of the split light spot before and after the simulated phase change, compared with the uniformly distributed light spot intensity before the phase change, it can be seen that the light spot undergoes polarization shift after the phase change, and the intensity of the split light spot on the upper side is significantly greater than that on the lower side. This can more intuitively show the regulatory effect of temperature on the optical spin Hall effect.

[0080] S2. Experimental verification:

[0081] S21. Build the experimental platform: Figure 5As shown, He-Ne laser 1, half-wave plate 2, short-focus lens 3, first Glan laser polarizer 4, VO2 film sample 5, second Glan laser polarizer 6, long focal length lens 7, CCD camera 8 are arranged in sequence along the direction of light propagation; because the dielectric constant of VO2 changes during the phase change process, its own complex refractive index changes accordingly, and its optical properties change. After the light beam is irradiated on the film surface, the spin component of the reflected light beam changes rapidly, causing the spin transverse shift to change. In order to observe this change intuitively, it is necessary to change the temperature of the sample to realize the thermo-optical control of the optical spin Hall effect. Therefore, a heater is installed at the bottom of the VO2 film sample 5 using thermal conductive glue and placed on a turntable bracket. At the same time, the CCD camera 8 is connected to the computer;

[0082] Among them, the function of the half-wave plate 2 is to adjust the light intensity so as not to exceed the load of the CCD camera 8 and cause damage to the lens; the function of the short-focus lens 3 is to focus the light beam; the first Glan laser polarizer 4 is used to adjust the polarization direction of the light so that the adjusted light beam presents a Gaussian distribution. The light beam adjusted by the first Glan laser polarizer 4 is irradiated on the surface of the VO2 thin film sample 5, and the optical spin Hall effect occurs on the surface of the VO2 thin film sample 5, and the light beam is transversely split in the vertical direction. However, since the transverse shift of the light beam is very small, the wave functions of different spin eigenstates will overlap to a large extent, so the light beam reflected from the surface of the VO2 thin film sample 5 needs to pass through the second Glan laser polarizer 6. The second Glan laser polarizer 6 is perpendicular to the first Glan laser polarizer 4, and the two spin components of the light beam are coherent, and the transverse shift of the light beam is significantly increased. The amplified light beam is collimated by the long focal length lens 7, and the intensity and displacement of the two split light beams are finally collected by the CCD camera 8 to observe the final spin transverse shift position change.

[0083] The heater described in step S21 is a heating electrode fixed on the solid prism.

[0084] S22, after preheating, setting the centroid position of the light spot at this time as the initial position;

[0085] Step S22 specifically includes the following steps:

[0086] S221. Before the experiment begins, the VO2 thin film sample 5 is preheated, the heater temperature is adjusted to 30°C, and maintained at this state for 10 minutes, so that the temperature of the VO2 thin film sample 5 is maintained at 30°C to maintain a relatively stable state;

[0087] At the beginning of the experiment, the temperature of the VO2 thin film sample 5 is maintained at 30°C, and the half-wave plate 2, the first Glan laser polarizer 4 and the second Glan laser polarizer 6 are adjusted to make the energy distribution of the two light spots uniform. The center of mass position of the light spot at this time is set as the initial position. On this basis, the movement of the center of mass position can be used as a pointer to the movement of the size of the optical spin Hall effect beam splitting.

[0088] S222, turn on the He-Ne laser light source 1 to emit a 632.8 nm laser beam. It should be noted that in order to avoid excessive beam intensity that exceeds the load of the CCD camera 8 and damages the lens, the lens of the CCD camera 8 should be properly shielded before adjusting the optical path;

[0089] S223, adjust the half-wave plate 3 to make the light intensity reach the set requirement, and then adjust the first Glan laser polarizer 4 and the second Glan laser polarizer 6 until two evenly distributed light spots are observed on the computer screen connected to the CCD camera 8. When the light spots are evenly distributed, the center of mass of the entire light field is equal to the center of mass of the light spot distribution. The light spot position at this time is defined as the initial state, and the lateral displacement value of the optical spin Hall effect is set to 0. The movement of the center of mass position is used as the lateral displacement value of the optical spin Hall effect. On this basis, a heating experiment is carried out.

[0090] S23, using a heater to conduct a heating experiment on the VO2 thin film sample 5, plotting a curve of the change of the center of mass position of the light spot with temperature, and taking the movement of the center of mass of the light spot as the lateral displacement value of the optical spin Hall effect;

[0091] Step S23 specifically includes the following steps:

[0092] S231, heating at intervals of 10°C, and when the heater shows that it has reached the set temperature, wait for 5 minutes, and measure the surface temperature of the VO2 film sample 5 with a temperature gun, and record the centroid position of the light spot;

[0093] S232. When the surface temperature of the VO2 film sample 5 reaches 60°C, the temperature rise interval can be adjusted to 2°C. Whenever the heater displays that the set temperature has been reached, wait for 5 minutes and measure the surface temperature of the VO2 film sample 5 with a temperature gun, while recording the centroid position of the light spot.

[0094] S233, when the phase transition temperature is reached, continue heating, and record the centroid position of the light spot;

[0095] S234. After reaching the set heating temperature, stop heating to make the VO2 thin film sample 5, and record the center of mass position of the light spot during the cooling process.

[0096] Example 2

[0097] like Figure 6As shown in the figure, as the temperature increases, the center of mass position of the light spot gradually moves. When the temperature is low, the movement speed is relatively slow, but when the temperature approaches the critical temperature of the VO2 phase transition, the change of the center of mass position is significantly intensified, reaching 400μm. This phenomenon shows that the movement of the center of mass of the light spot is affected by the temperature as the temperature gradually increases. When the temperature exceeds the phase transition temperature, the change of the center of mass position becomes flat again, suggesting that after the phase transition occurs, the optical properties of the VO2 film have changed dramatically, causing the optical spin Hall effect on the surface of the sample to change.

[0098] The explanation for this phenomenon involves the phase change behavior of VO2. At low temperatures, the structure of the VO2 film is relatively stable, so the position of the center of mass of the light spot changes slowly. As the temperature rises, the lattice structure inside the material changes, which causes significant changes in the properties of the material, which in turn affects the movement of the center of mass of the light spot. When approaching the phase change temperature, the complex refractive index of the VO2 film changes dramatically, and the optical spin Hall effect on the surface of the sample becomes stronger, resulting in a rapid change in the position of the center of mass of the light spot. Once the phase change is completed, the properties of the material tend to stabilize, and the movement of the center of mass of the light spot will become smooth again.

[0099] At the beginning of the experiment, the optical spin Hall effect occurs on the surface of the VO2 film, and the incident light is split into two circularly polarized lights. After being amplified by the experimental platform, they appear as two light spots with uniform energy distribution. As the temperature rises, the energy distribution of the light spots is no longer uniform. The energy of the upper light spot is gradually higher than that of the lower light spot, and the center of mass of the light spot also moves upward. This is because the properties of the sample surface change slightly with the increase of temperature during the heating process, such as Figure 7 As shown in the figure, the energy distribution diagram of the light spot at 70℃ has changed significantly. The energy of the upper light spot is higher, while the energy of the lower light spot is close to disappearing, which means that after exceeding 68℃, VO2 has undergone a phase change, the complex refractive index has changed, and the conductivity has changed by several orders of magnitude, from an insulating state to a metallic state on a macroscopic scale. The optical spin Hall effect on its surface has also changed due to the existence of the refractive index gradient. The spin transverse shift of the two split circularly polarized lights has increased significantly, effectively realizing the thermal-optical regulation of the optical spin Hall effect.

[0100] S3. Cross-validation: Compare the results of step S13 and step S23 to determine the feasibility of using temperature to control the optical spin Hall effect of VO2 thin film.

[0101] It can be seen from the results obtained in Example 1 and Example 2 that the two show similar trends, which verifies that the photo-spin Hall effect can be regulated by temperature. There is a certain quantitative relationship between the PSHE shift and temperature, which verifies the feasibility of thermo-optical regulation of the photo-spin Hall effect and provides a new way to control the photo-spin Hall effect.

[0102] Therefore, the present invention adopts the above-mentioned verification method of thermo-optical regulation of optical spin Hall effect based on VO2 thin film, and cross-verifies the thermo-optical regulation of optical spin Hall effect through simulation and experimental cross-verification, providing a new way to use thermotropic phase change materials to regulate optical properties.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A verification method for the thermo-optical control of the optical spin Hall effect based on VO2 thin film, characterized by: The following steps are involved: S1. Simulation experiment verification: S11, preparing VO2 thin film samples; The VO2 thin film sample described in step S11 includes a VO2 thin film and a sapphire substrate located at the bottom of the VO2 thin film; S12. According to Snell's law, a propagation model of the light beam in the medium is established to solve the reflection coefficient of the VO2 thin film sample; Step S12 specifically includes the following steps: S121. Assuming the incident wavelength of the laser beam to be 633 nm, according to Snell's law, the Fresnel reflection coefficients of the s-wave and p-wave are expressed as: (1) In the formula, Indicates air and Fresnel reflection coefficient of s-polarized light at the film interface; Indicates air and Fresnel reflection coefficient of p-polarized light at the film interface; express Fresnel reflection coefficient of s-polarized light at the interface between the film and the sapphire substrate; express Fresnel reflection coefficient of p-polarized light at the interface between the film and the sapphire substrate; represents the refractive index of air; represents the refractive index of VO2 thin film; represents the refractive index of the sapphire substrate; They represent the angles of the light beam when it enters different dielectric layers; S122. Derivation of the Fresnel reflection coefficient of s-polarized light of VO2 thin film samples and p-polarized light Fresnel reflectance : (2) In the formula, It represents the optical path difference caused by the light beam passing through the VO2 film: (3) In the formula, represents the free space wavelength, Indicates the thickness of VO2 film; S13. Based on the principle of geometric optics, the lateral shift value of the optical spin Hall effect on the surface of the VO2 thin film sample before and after the phase change is solved; In step S13, the lateral displacement of the spin component of the beam is established by using the principle of geometric optics. Numerical calculation model of: (4) In the formula, Indicates the magnification angle; represents the incident light wave vector; represents the Rayleigh distance; S2. Experimental verification: S21. Build an experimental platform: Arrange He-Ne laser, half-wave plate, short-focus lens, first Glan laser polarizer, VO2 thin film sample, second Glan laser polarizer, long-focus lens, CCD camera in sequence along the direction of light propagation, install a heater at the bottom of the VO2 thin film sample, and connect the CCD camera to the computer; S22, after preheating, setting the centroid position of the light spot at this time as the initial position; S23. A heating experiment was conducted on the VO2 thin film sample using a heater, and a curve of the change of the center of mass position of the light spot with temperature was plotted, and the movement of the center of mass of the light spot was used as the lateral displacement value of the optical spin Hall effect; Step S23 specifically includes the following steps: S231, heating at intervals of 10°C, and when the heater shows that it has reached the set temperature, wait for 5 minutes, and measure the surface temperature of the VO2 film sample with a temperature gun, and record the centroid position of the light spot; S232. When the surface temperature of the VO2 film sample reaches 60°C, the heating interval can be adjusted to 2°C. Whenever the heater displays that it has reached the set temperature, wait for 5 minutes and measure the surface temperature of the VO2 film sample with a temperature gun, while recording the centroid position of the light spot. S233, when the phase transition temperature is reached, continue heating, and record the centroid position of the light spot; S234, after reaching the set heating temperature, stop heating to make the VO2 thin film sample, and record the centroid position of the light spot during the cooling process; S3. Cross-validation: Compare the results of step S13 and step S23 to determine the feasibility of using temperature to control the optical spin Hall effect of VO2 thin film.

2. The verification method of the thermo-optically controlled optical spin Hall effect based on VO2 thin film according to claim 1 is characterized in that: The heater described in step S21 is a heating electrode fixed on the solid prism.

3. The verification method of the thermo-optically controlled optical spin Hall effect based on VO2 thin film according to claim 2 is characterized in that: Step S22 specifically includes the following steps: S221. Before the experiment begins, preheat the VO2 film sample, adjust the heater temperature to 30°C, and maintain it at this state for 10 minutes to keep the VO2 film sample temperature at 30°C to maintain a relatively stable state; S222, turn on the He-Ne laser light source to emit a 632.8 nm laser beam; S223. Adjust the half-wave plate to make the light intensity reach the set requirement, and then adjust the first Glan laser polarizer and the second Glan laser polarizer until two evenly distributed light spots are observed on the computer screen connected to the CCD. When the light spots are evenly distributed, the center of mass of the entire light field is equal to the center of mass of the light spot distribution. The position of the light spot at this time is defined as the initial state, and the lateral shift value of the optical spin Hall effect is set to 0. The movement of the center of mass position is used as the lateral shift value of the optical spin Hall effect. On this basis, a heating experiment is carried out.

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