A dynamic modulation metasurface based on phase change material and a preparation method thereof

Abstract

The application discloses a kind of dynamic modulation metasurface based on phase change material and preparation method thereof.The metasurface is composed of unit arranged in two-dimensional square lattice, and the unit structure is multilayer film on the substrate, and there is composite nanocolumn on the multilayer film.By designing the number of layers and thickness of multilayer film and selecting appropriate unit structure period and the size of nanocolumn, the refractive index change generated in the material phase change process is used to realize the dynamic control of the transmittance and wavefront phase of the transmitted light beam.Using the refractive index change in the phase change process and the phase modulation difference of the long and short axes of the composite nanocolumn, the switching of the three polarization states of the outgoing light can be realized, and the transmittance can be reduced by about one order of magnitude synchronously.The application improves the control dimension of the optical modulation metasurface, reduces the size of the device, and improves the integrability of the device.

Description

Technical Field

[0001] This invention relates to beam shaping and spatial light field modulation technology, specifically to a dynamic modulation metasurface based on the light transmittance-wavefront phase-polarization state of phase change materials and its preparation method, which is applicable to dynamic light modulators with operating wavelengths of 2 to 6 μm. Background Technology

[0002] Artificial microstructure metasurfaces are two-dimensional surfaces composed of periodic or aperiodic subwavelength micro / nano arrays. Through the design of subwavelength structures, they allow for arbitrary modulation of electromagnetic wave amplitude, phase, polarization, and other dimensions, exhibiting powerful electromagnetic wave manipulation capabilities and leading to applications such as superlenses, anomalous reflections, and perfect absorption. Phase change materials, such as Ge₂Sb₂Te₅, can alter their refractive index by controlling conditions like temperature and voltage. Their inclusion expands the controllability of artificial microstructure metasurfaces, providing a feasible path for dynamic control. Artificial microstructure metasurfaces based on phase change materials can effectively solve the problems of large size, difficult debugging, and limited functionality in traditional optical devices. Their subwavelength characteristics enable dynamic control of light amplitude, phase, polarization, and other dimensions at the micro / nano scale, with significant applications in the miniaturization, integration, and multi-dimensional detection of photodetectors.

[0003] Currently, metasurface designs based on phase change materials can separately control the amplitude and phase of electromagnetic waves. However, metasurface designs capable of jointly manipulating multiple dimensions such as phase, amplitude, and polarization still face many challenges. Furthermore, previously reported dynamic metasurfaces based on phase change materials only control polarization states in two states: on and off, failing to fully utilize the intermediate states during phase transitions, thus limiting the number of controllable states. This invention addresses these problems with phase change material metasurfaces by proposing a multi-dimensional dynamic modulation metasurface based on light transmittance, wavefront phase, and polarization state, along with its fabrication method. This effectively increases the controllable dimensions and number of states of the optical modulation metasurface, reduces device size, and improves device integrability, with significant applications in enhancing detector dynamic range and multi-dimensional detection. Summary of the Invention

[0004] This invention addresses the problems of large size and limited functionality of traditional optical modulators by providing a dynamic modulation metasurface based on phase change materials and its preparation method.

[0005] The dynamically modulated metasurface is composed of units arranged in a two-dimensional square lattice, with the period P of the unit lattice being 1000nm to 3000nm.

[0006] The unit structure is as follows: a multilayer film 2 is on the substrate 3 and a composite material nanopillar 1 is on the multilayer film 2. The composite material nanopillar 1 is composed of elliptical nanopillar 1-2 and elliptical hollow nanopillar 1-1.

[0007] The substrate 3 is made of silicon dioxide, barium fluoride, magnesium fluoride, or sapphire.

[0008] The multilayer film structure 2 is composed of alternating growth of dielectric material and phase change material. The dielectric material is silicon or germanium, and the phase change material is Ge2Sb2Te5, Ge2Sb2Se1Te4 or Ge2Sb2Se3Te2. The thickness of each film layer is 30nm to 320nm, and the number of layers is 3 to 8.

[0009] The composite nanopillar 1 is composed of elliptical nanopillar 1-2 and elliptical hollow nanopillar 1-1. The elliptical nanopillar 1-2 is made of Ge2Sb2Te5, Ge2Sb2Se1Te4, or Ge2Sb2Se3Te2, and the elliptical hollow nanopillar 1-1 is made of silicon or germanium. The elliptical nanopillar 1-2 and the elliptical hollow nanopillar 1-1 have the same height, ranging from 800 nm to 3000 nm. The outer radius R of the composite nanopillar 1 and the elliptical hollow nanopillar 1-1 is... x and R y The wavelength range is 150 nm to 1400 nm, and the outer radius of the elliptical nanopillar 1-2 is r. x and r y Duty cycle r x / R x and r y / R y The value is 0.5 to 0.65, and the rotation angle α is 0 to π radians.

[0010] This invention provides a method for establishing a dynamically modulated metasurface based on phase change materials, comprising the following steps:

[0011] 1) Thin films are sequentially grown on substrate 3 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form multilayer films 2 with a thickness of 30 nm to 320 nm per layer;

[0012] 2) A dielectric material thin film is grown on the multilayer film 2 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a dielectric layer with a thickness of 800 nm to 3000 nm.

[0013] 3) Elliptical nanopore patterns arranged in a certain pattern are formed on the dielectric layer by pattern generation methods such as electron beam lithography, nanoimprinting or ultraviolet lithography;

[0014] 4) The exposed dielectric layer is etched using dry or wet etching methods to form a nanopore array without stripping the photoresist.

[0015] 5) Continue to grow phase change material films using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form phase change material films with a thickness of 800 nm to 3000 nm on the pores and photoresist;

[0016] 6) Peel off the photoresist and the phase change material film on the photoresist to form a dielectric layer with regularly arranged phase change material nanopillars embedded in it.

[0017] 7) A pattern of nanopillar arrays arranged in a certain pattern is formed on the dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography;

[0018] 8) The exposed dielectric layer is etched by dry etching or wet etching to form a composite nanopillar array.

[0019] After adopting the above technical solution, the present invention has the following beneficial effects: By using the method of combined phase and amplitude modulation, the light intensity at the focused spot can be continuously adjusted according to the phase transition rate. By utilizing the change in refractive index during the phase transition and the phase modulation difference of the long and short axes of the composite material nanopillars, the switching of the three polarization states of the emitted light can be achieved, and the transmittance can be synchronously adjusted to decrease by about one order of magnitude sequentially. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein,

[0021] Figure 1 This is a schematic diagram of the square lattice unit of the dynamically modulated metasurface based on phase change material in Examples 1, 2, 3, and 4 of this invention;

[0022] The numbers in the attached diagram are:

[0023] 1. Composite material nanopillars;

[0024] 1-2 are elliptical nanopillars;

[0025] 1-1 is an elliptical hollow nanopillar;

[0026] 2. Multilayer film;

[0027] 3. Substrate;

[0028] Figure 2 This is a top view of the square lattice unit of the dynamically modulated metasurface based on phase change material in embodiments 1, 2, 3, and 4 of this invention;

[0029] Figure 3 This is the transmission spectrum of incident light passing through the unit structure in Embodiment 1 of the present invention;

[0030] Figure 4This refers to the transmission phase of the incident light through the unit structure in Embodiment 1 of the present invention;

[0031] Figure 5 This refers to the changes in transmittance and focusing efficiency of the dynamically modulated metasurface as a function of phase transition rate in Example 1 of this invention.

[0032] Figure 6 This is the transmission spectrum of incident light passing through the unit structure in Embodiment 2 of the present invention;

[0033] Figure 7 This refers to the transmission phase of the incident light through the unit structure in Embodiment 2 of the present invention;

[0034] Figure 8 This refers to the changes in transmittance and focusing efficiency of the dynamically modulated metasurface as a function of phase transition rate in Example 2 of this invention.

[0035] Figure 9 This is the transmission spectrum of incident light passing through the unit structure in Embodiment 3 of the present invention;

[0036] Figure 10 This refers to the transmission phase of the incident light through the unit structure in Embodiment 3 of the present invention;

[0037] Figure 11 This refers to the changes in transmittance and focusing efficiency of the dynamically modulated metasurface as a function of phase transition rate in Example 3 of this invention.

[0038] Figure 12 The transmittance of x- and y-polarized light by the supercell in Embodiment 4 of this invention at different phase transition rates when the rotation angle is 0.

[0039] Figure 13 This refers to the transmission phase difference of x- and y-polarized light at different phase transition rates when the rotation angle is 0 in the super-unit of Embodiment 4 of the present invention. Detailed Implementation

[0040] Example 1

[0041] A dynamically modulated metasurface based on phase change materials is composed of 51*51 square lattice units, as shown in the schematic diagram of the unit. Figure 1 Each unit comprises a composite nanopillar 1, a multilayer film 2, and a substrate 3, with a working wavelength of 3.3 μm.

[0042] The composite nanopillar 1 consists of 1-1 and 1-2, where 1-2 is made of Ge₂Sb₂Te₅ and 1-1 is made of Si. The nanopillar unit has a period of 1.6 μm, a height of 2 μm, and a duty cycle r. x / R x and r y / R y The value is 0.5, and the nanopillar is cylindrical, i.e., rx =r y And R x = / R y The multilayer film is designed to achieve high transmittance when the phase transition material is in the amorphous state at a working wavelength of 3.3 μm, and low transmittance when it transitions to the crystalline state. After optimization of the number of layers and thickness, the multilayer film consists of three layers, with the materials and thicknesses from bottom to top being: Ge2Sb2Te5 (180 nm), Si (50 nm), and Ge2Sb2Te5 (160 nm). The substrate is sapphire. To achieve dynamic control of the emitted light from high transmittance and focusing to low transmittance and unfocusing during the phase transition from amorphous to crystalline state, based on the principle of equal optical path length, the phase difference that needs to be compensated in the amorphous composite nanopillar array is... satisfy:

[0043]

[0044] Where (x, y) are the center coordinates of the composite nanopillar, the focal length is f, and the working wavelength is λ. Figure 3 To achieve the desired working wavelength of 3.3 μm, the radius R of the composite nanopillars... x Transmittance change curves before and after phase transition. Figure 4 To achieve the desired working wavelength of 3.3 μm, the radius R of the composite nanopillars... x The phase change curves before and after the phase transition are shown. Based on the above focusing formula, the unit sizes that meet the phase requirements are selected and arranged into a 51*51 array. This metasurface can meet the requirement of dynamically controlling the incident light from high-transmission focusing to low-transmission non-focusing during the phase transition of the material from amorphous to crystalline state.

[0045] The above-mentioned method for establishing a dynamically modulated metasurface based on phase change materials includes the following steps:

[0046] 1) Thin films are sequentially grown on substrate 3 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a multilayer film 2 consisting of Ge2Sb2Te5 (180nm), Si (50nm) and Ge2Sb2Te5 (160nm) from bottom to top;

[0047] 2) A Si dielectric material thin film is grown on the multilayer film 2 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a dielectric layer with a thickness of 2000 nm.

[0048] 3) Elliptical nanopore patterns arranged in a certain pattern are formed on the dielectric layer by pattern generation methods such as electron beam lithography, nanoimprinting or ultraviolet lithography;

[0049] 4) The exposed dielectric layer is etched using dry or wet etching methods to form a nanopore array without stripping the photoresist.

[0050] 5) Ge2Sb2Te5 phase change material thin films were further grown using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form a 2000nm thick Ge2Sb2Te5 phase change material thin film on the holes and photoresist.

[0051] 6) Peel off the photoresist and the phase change material film on the photoresist to form a dielectric layer with regularly arranged phase change material nanopillars embedded in it.

[0052] 7) A pattern of nanopillar arrays arranged in a certain pattern is formed on the dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography;

[0053] 8) The exposed dielectric layer is etched by dry etching or wet etching to form a composite nanopillar array.

[0054] Figure 5 The changes in transmittance and focusing efficiency of the dynamically modulated metasurface with varying Ge2Sb2Te5 phase transition rate are shown. It can be seen that as the Ge2Sb2Te5 phase transition rate gradually increases, the light intensity on the focal plane gradually decreases, the transmittance gradually decreases, and the focusing efficiency gradually decreases. That is, Example 1 can achieve dynamic control of incident light from high transmittance focusing to low transmittance non-focusing at a focal depth of 3.3 μm.

[0055] Example 2

[0056] A dynamically modulated metasurface based on phase change materials is composed of 41*41 square lattice units, as shown in the schematic diagram of the unit. Figure 1 Each unit comprises a composite nanopillar 1, a multilayer film 2, and a substrate 3, with a working wavelength of 2μm.

[0057] The composite nanopillar 1 consists of 1-1 and 1-2, where 1-2 is made of Ge₂Sb₂Se₃Te₂ and 1-1 is made of Si. The period of each nanopillar unit is 1 μm, the height is 0.8 μm, and the duty cycle r is... x / R x and r y / R y The value is 0.5, and the nanopillar is cylindrical, i.e., r x =r y And R x = / R yThe multilayer film is designed to achieve high transmittance when the phase change material is in the amorphous state at a working wavelength of 2 μm, and low transmittance when it transitions to the crystalline state. After optimization of the number of layers and thickness, the multilayer film consists of three layers, with the materials and thicknesses from bottom to top being: Ge2Sb2Se3Te2 (110 nm), Si (30 nm), and Ge2Sb2Se3Te2 (100 nm). The substrate is SiO2. To achieve dynamic control of the emitted light from high transmittance focusing to low transmittance unfocusing during the phase transition from amorphous to crystalline state, based on the principle of equal optical path length, the phase difference that needs to be compensated in the amorphous composite nanopillar array is... satisfy:

[0058]

[0059] Where (x, y) are the center coordinates of the composite nanopillar, the focal length is f, and the working wavelength is λ. Figure 6 To achieve a working wavelength of 2 μm, the radius R of the composite nanopillars... x Transmittance change curves before and after phase transition. Figure 7 To achieve a working wavelength of 2 μm, the radius R of the composite nanopillars... x The phase change curves before and after the phase transition are shown. Based on the above focusing formula, the unit sizes that meet the phase requirements are selected and arranged into a 41*41 array. This metasurface can meet the requirement of dynamically controlling the incident light from high-transmission focusing to low-transmission non-focusing during the phase transition of the material from amorphous to crystalline state.

[0060] The above-mentioned method for establishing a dynamically modulated metasurface based on phase change materials includes the following steps:

[0061] 1) Thin films are sequentially grown on substrate 3 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a multilayer film 2 consisting of Ge2Sb2Se3Te2 (110nm), Si (30nm) and Ge2Sb2Se3Te2 (100nm) from bottom to top;

[0062] 2) A Si dielectric material thin film with a thickness of 800 nm is grown on the multilayer film 2 by plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering.

[0063] 3) Elliptical nanopore patterns arranged in a certain pattern are formed on the dielectric layer by pattern generation methods such as electron beam lithography, nanoimprinting or ultraviolet lithography;

[0064] 4) The exposed dielectric layer is etched using dry or wet etching methods to form a nanopore array without stripping the photoresist.

[0065] 5) Continue to grow Ge2Sb2Se3Te2 phase change material thin films using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form an 800nm ​​thick Ge2Sb2Se3Te2 phase change material thin film on the holes and photoresist;

[0066] 6) Peel off the photoresist and the phase change material film on the photoresist to form a dielectric layer with regularly arranged phase change material nanopillars embedded in it.

[0067] 7) A pattern of nanopillar arrays arranged in a certain pattern is formed on the dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography;

[0068] 8) The exposed dielectric layer is etched by dry etching or wet etching to form a composite nanopillar array.

[0069] Figure 8 The diagram shows the changes in transmittance and focusing efficiency of a dynamically modulated metasurface as the phase transition rate of Ge2Sb2Se3Te2 changes. It can be seen that as the phase transition rate of Ge2Sb2Se3Te2 gradually increases, the transmittance gradually decreases, while the focusing efficiency first increases and then decreases. That is, Example 2 can achieve dynamic control of incident light from high transmittance focusing to low transmittance non-focusing at a range of 2µm.

[0070] Example 3

[0071] A dynamically modulated metasurface based on phase change materials is composed of 41*41 square lattice units, as shown in the schematic diagram of the unit. Figure 1 Each unit comprises a composite nanopillar 1, a multilayer film 2, and a substrate 3, with a working wavelength of 6 μm.

[0072] The composite nanopillar 1 consists of 1-1 and 1-2, where 1-2 is made of Ge₂Sb₂Se₁Te₄ and 1-1 is made of Ge. The nanopillar unit has a period of 3 μm, a height of 3 μm, and a duty cycle r. x / R x and r y / R y The value is 0.65, and the nanopillar is cylindrical, i.e., r x =r yAnd Rx = / Ry. The multilayer film is designed to have high transmittance when the phase change material is in the amorphous state at the working wavelength of 6μm, and low transmittance when it transitions to the crystalline state. After optimization of the number of layers and thickness, the multilayer film consists of 8 layers, with the materials and thicknesses from bottom to top as follows: Ge2Sb2Se1Te4 (320nm), Ge (75nm), Ge2Sb2Se1Te4 (270nm), Ge (75nm), Ge2Sb2Se1Te4 (320nm), Ge (75nm), Ge2Sb2Se1Te4 (270nm), Ge (30nm). The substrate is BaF2. In order to achieve dynamic control of the emitted light from high transmittance focusing to low transmittance unfocusing during the phase transition from the amorphous to the crystalline state, based on the principle of equal optical path, the phase difference that needs to be compensated in the amorphous composite nanopillar array is... satisfy:

[0073]

[0074] Where (x, y) are the center coordinates of the composite nanopillar, the focal length is f, and the working wavelength is λ. Figure 9 To achieve the desired working wavelength of 6 μm, the radius R of the composite nanopillars... x Transmittance change curves before and after phase transition. Figure 10 To achieve the desired working wavelength of 6 μm, the radius R of the composite nanopillars... x The phase change curves before and after the phase transition are shown. Based on the above focusing formula, the unit sizes that meet the phase requirements are selected and arranged into a 41*41 array. This metasurface can meet the requirement of dynamically controlling the incident light from high-transmission focusing to low-transmission non-focusing during the phase transition of the material from amorphous to crystalline state.

[0075] The above-mentioned method for establishing a dynamically modulated metasurface based on phase change materials includes the following steps:

[0076] 1) Thin films are sequentially grown on substrate 3 using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form a multilayer film 2 consisting of Ge2Sb2Se1Te4 (320nm), Ge (75nm), Ge2Sb2Se1Te4 (270nm), Ge (75nm), Ge2Sb2Se1Te4 (320nm), Ge (75nm), Ge2Sb2Se1Te4 (270nm), and Ge (30nm) from bottom to top;

[0077] 2) A Ge dielectric material thin film is grown on the multilayer film 2 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a Ge dielectric layer with a thickness of 3000 nm.

[0078] 3) Elliptical nanopore patterns arranged in a certain pattern are formed on the dielectric layer by pattern generation methods such as electron beam lithography, nanoimprinting or ultraviolet lithography;

[0079] 4) The exposed dielectric layer is etched using dry or wet etching methods to form a nanopore array without stripping the photoresist.

[0080] 5) Ge2Sb2Se1Te4 phase change material thin films were further grown using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form a 3000nm thick phase change material thin film on the holes and photoresist.

[0081] 6) Peel off the photoresist and the phase change material film on the photoresist to form a dielectric layer with regularly arranged phase change material nanopillars embedded in it.

[0082] 7) A pattern of nanopillar arrays arranged in a certain pattern is formed on the dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography;

[0083] 8) The exposed dielectric layer is etched by dry etching or wet etching to form a composite nanopillar array.

[0084] Figure 11 The diagram shows the changes in transmittance and focusing efficiency of a dynamically modulated metasurface as the phase transition rate of Ge2Sb2Se1Te4 changes. It can be seen that as the phase transition rate of Ge2Sb2Se1Te4 gradually increases, the transmittance gradually decreases, and the focusing efficiency gradually decreases. That is, Example 3 can achieve dynamic control of incident light from high transmittance focusing to low transmittance non-focusing at a wavelength of 6µm.

[0085] Example 4

[0086] A dynamic modulation metasurface based on phase change materials is composed of 51*51 square lattice units, as shown in the schematic diagram of the unit. Figure 1 Each unit comprises a composite nanopillar 1, a multilayer film 2, and a substrate 3, with a working wavelength of 3.3 μm.

[0087] The composite nanopillar 1 consists of 1-1 and 1-2, with 1-2 made of Ge2Sb2Te5 and 1-1 made of Si. The period of each nanopillar unit is 1.6 μm, and the height is 2 μm. The radii of the two axes of the elliptical cylinder 1-1 are rx = 190 nm and ry = 170 nm, respectively, while the radii of the two axes of the hollow elliptical cylinder 1-2 are Rx = 370 nm and Ry = 280 nm, respectively. The multilayer film is designed to have high transmittance when the phase change material is in the amorphous state at the working wavelength of 3.3 μm, and low transmittance when it transitions to the crystalline state. After optimization of the number of layers and thickness, the multilayer film consists of three layers, with the materials and thicknesses from bottom to top being: Ge2Sb2Te5 (180 nm), Si (50 nm), and Ge2Sb2Te5 (160 nm). The substrate is sapphire.

[0088] Figure 12 and Figure 13 For different phase transition rates, the transmittance and transmission phase difference of the superunit in Example 4 for x- and y-polarized light at a rotation angle of 0 are shown. It can be seen that when the phase transition rate is 0, 0.4, and 1, the transmittance of the superunit for x- and y-polarized light is almost the same, but the phases differ by π / 2, π, and 0, respectively. That is, after arranging this superunit into a 51*51 array according to the vortex phase, when subjected to left-handed or right-handed circularly polarized incident light, three types of light can be emitted: a vortex beam with a linear polarization vector, a cross-polarized vortex beam, and a co-polarized parallel beam, with the transmittance gradually decreasing by approximately one order of magnitude. When the topological charge of the emitted vortex light is 4, the phase difference that the composite nanopillar array needs to compensate for is... satisfy:

[0089]

[0090] in, The unit is degrees, (x, y) is the center coordinate of the composite nanopillar, and θ is its corresponding azimuth angle. When the phase transition rate is 0.4, the superelement satisfies the geometric phase condition, and the rotation angle α of the nanopillar, according to geometric phase theory, satisfies the following equation:

[0091]

[0092] The vortex array is arranged according to the geometric phase theory, and the rotation angle of each nanopillar is determined by its azimuth angle θ.

[0093] This invention provides a method for establishing the above-mentioned dynamically modulated metasurface based on phase change materials, comprising the following steps:

[0094] 1) A thin film is grown on the substrate 3 by plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering, forming a multilayer film 2 of Ge2Sb2Te5 (180nm), Si (50nm) and Ge2Sb2Te5 (160nm) sequentially from bottom to top;

[0095] 2) A Si dielectric material thin film is grown on the multilayer film 2 using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a dielectric layer with a thickness of 2000 nm.

[0096] 3) A pattern of nanopores arranged in a certain pattern is formed on the Si dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography.

[0097] 4) The exposed dielectric layer is etched using dry or wet etching methods to form a nanopore array without stripping the photoresist.

[0098] 5) Ge2Sb2Te5 phase change material thin films were further grown using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form a 2000nm thick Ge2Sb2Te5 phase change material thin film on the holes and photoresist.

[0099] 6) Peel off the photoresist and the Ge2Sb2Te5 phase change material film on the photoresist to form a dielectric layer with regularly arranged Ge2Sb2Te5 phase change material nanopillars embedded in it.

[0100] 7) A pattern of nanopillar arrays arranged in a certain pattern is formed on the Si dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography.

[0101] 8) The exposed Si dielectric layer is etched by dry etching or wet etching to form a nanopillar array of composite material.

[0102] When right-handed light is incident on the above array, at a phase transition rate of 0, the left-handed component of the far-field outgoing beam is about an order of magnitude smaller than the right-handed component, and the outgoing polarization state is a linearly polarized, well-fit vortex beam. At a phase transition rate of 0.4, the left-handed and right-handed components are on the same order of magnitude, and a portion of the right-handed component is converted into left-handed vortex light. At a phase transition rate of 1, the left-handed component is about three orders of magnitude smaller than the right-handed component, meaning the outgoing light is parallel light with its original polarization. At phase transition rates of 0 and 0.4, a vortex phase distribution with a topological charge of 4 can be observed in the far-field phase, proving the generation of vortex beams.

Claims

1. A dynamically modulated metasurface based on phase change materials, characterized in that: The dynamically modulated metasurface is composed of units arranged in a two-dimensional square lattice, with the period P of the unit lattice being 1000nm to 3000nm. The unit structure is as follows: a multilayer film (2) is on the substrate (3) and a composite material nanopillar (1) is on the multilayer film (2), wherein the composite material nanopillar (1) is composed of elliptical nanopillar (1-2) and elliptical hollow nanopillar (1-1); The substrate (3) is silicon dioxide, barium fluoride or sapphire; The multilayer film structure is composed of alternating growth of dielectric material and phase change material. The dielectric material is silicon or germanium, and the phase change material is Ge2Sb2Te5, Ge2Sb2Se1Te4 or Ge2Sb2Se3Te2. The thickness of each film layer is 30nm to 320nm, and the number of layers is 3 to 8. The composite nanopillar (1) consists of elliptical nanopillars (1-2) and elliptical hollow nanopillars (1-1). The elliptical nanopillars (1-2) are made of Ge2Sb2Te5, Ge2Sb2Se1Te4, or Ge2Sb2Se3Te2, and the elliptical hollow nanopillars (1-1) are made of silicon or germanium. The elliptical nanopillars (1-2) and elliptical hollow nanopillars (1-1) have the same height, ranging from 800 nm to 3000 nm. The outer radius R of the composite nanopillars (1) and elliptical hollow nanopillars (1-1) is... x and R y The wavelength range is 150 nm to 1400 nm, and the outer radius of the elliptical nanopillar (1-2) is r. x and r y Duty cycle r x / R x and r y / R y The value is 0.5 to 0.65, and the rotation angle α is 0 to π radians.

2. A method for preparing a dynamically modulated metasurface based on a phase change material as described in claim 1, characterized in that... Includes the following steps: 1) Thin films are grown sequentially on the substrate (3) using plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form multilayer films with a thickness of 30 nm to 320 nm per layer (2); 2) A dielectric material thin film is grown on the multilayer film (2) by plasma-enhanced chemical vapor deposition, electron beam evaporation or magnetron sputtering to form a dielectric layer with a thickness of 800 nm to 3000 nm. 3) Elliptical nanopore patterns arranged in a certain pattern are formed on the dielectric layer by pattern generation methods such as electron beam lithography, nanoimprinting or ultraviolet lithography; 4) The exposed dielectric layer is etched using dry or wet etching methods to form a nanopore array without stripping the photoresist. 5) Continue to grow phase change material films using plasma-enhanced chemical vapor deposition, electron beam evaporation, or magnetron sputtering to form phase change material films with a thickness of 800 nm to 3000 nm on the pores and photoresist; 6) Peel off the photoresist and the phase change material film on the photoresist to form a dielectric layer with regularly arranged phase change material nanopillars embedded in it. 7) A pattern of nanopillar arrays arranged in a certain pattern is formed on the dielectric layer by patterning methods such as electron beam lithography, nanoimprint lithography or ultraviolet lithography; 8) The exposed dielectric layer is etched by dry etching or wet etching to form a composite nanopillar (1) array.

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