A chalcogenide phase-change super-structured surface device with light field phase modulation

Abstract

The present application relates to a kind of chalcogenide phase change super-structure surface devices with light field phase modulation.It includes successively from bottom to top: dielectric substrate, reflective layer, dielectric isolation layer, chalcogenide phase change microstructure and dielectric protective layer;By adjusting the geometric parameter of chalcogenide phase change super-structure surface device, the resonance center wavelength of the dielectric resonance mode supported when the chalcogenide phase change microstructure is amorphous is close to target wavelength, the absorption of chalcogenide phase change microstructure after crystallization at target wavelength is reduced, to improve the spatial light field phase modulation efficiency of chalcogenide phase change super-structure surface device.The chalcogenide phase change super-structure surface device provided in the present application reduces the absorption of chalcogenide phase change microstructure after crystallization at target wavelength on the basis of ensuring certain phase modulation depth, improves the minimum reflectivity of chalcogenide phase change super-structure in the phase change process of chalcogenide phase change material, to improve the efficiency of spatial light field phase modulation of chalcogenide phase change super-structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light field modulation, and more particularly to a chalcogenide phase-change super-structured surface device with light field phase modulation. BACKGROUND

[0002] Most of the conventional spatial light modulators use liquid crystals as active materials. Due to the response speed of liquid crystal molecules, the modulation rate of the conventional spatial light modulators is difficult to break through 10 kHz. In addition, the refractive index variation range of liquid crystals is small, which leads to a large volume of the conventional spatial light modulators and a large number of pixel points, making it difficult to realize large-scale high-density integration on a chip and unable to meet the needs of large-scale high-density integrated optoelectronic systems in the fields of consumer electronics, medical detection and aerospace. Super-structured surface is a kind of ultra-thin two-dimensional structure array composed of anisotropic or isotropic artificial scatterers with subwavelength size arranged on a substrate at subwavelength intervals, which is considered as the third generation of new optical devices after the first generation of catadioptric optical elements and the second generation of diffractive optical elements. According to the generalized Snell law, by changing the geometric parameters of micro-nano structures and the refractive index contrast between them and the environment medium, the phase, transmittance and reflectance parameters can be introduced at the interface, and then almost all electromagnetic wave parameters can be arbitrarily controlled, which provides a new idea for large-scale high-density integrated spatial light modulators.

[0003] In recent years, many scholars have combined different active materials with super-structured surfaces to construct dynamic super-structured surfaces that can be actively controlled. By exciting the active materials through external conditions such as electricity, heat, light and mechanical stretching, and changing various physical properties of the active materials, the originally fixed and uncontrolled static super-structured surfaces have adjustable and reconfigurable characteristics, enhancing the flexibility of super-structured surface devices and expanding their application scenarios. Common active materials include transparent conductive oxides, liquid crystal materials and semiconductor materials, etc.

[0004] Chalcogenide phase change material is a material that can reversibly switch between crystalline and amorphous states at high speed, and each state is non-volatile. Due to the significant changes in optical, electrical and thermal properties during the phase change, it is widely used as an active material to control various super-structured surface devices at high speed. Chalcogenide phase change material has many advantages, such as fast phase change speed, low phase change power consumption, high cycle number, no static power consumption and compatibility with CMOS process, etc. It is a mature and promising active material. However, the extinction coefficient of the amorphous state of chalcogenide phase change material is generally small, but the extinction coefficient of the crystalline state is not negligible. With the increase of crystallization rate, the extinction coefficient gradually increases, and in the completely crystalline state, the extinction coefficient reaches the maximum. At the same time, as an active material, chalcogenide phase change material is often located at the position where the light field localization of the active super-structured surface is the strongest, and the weak extinction coefficient will also cause great loss. This inherent disadvantage makes chalcogenide phase change super-structured surface devices mostly used for amplitude modulation of spatial light field, and the efficiency of phase modulation of spatial light field is low. SUMMARY

[0005] The present application is to overcome the defect that the efficiency of phase modulation of spatial light field is low in the prior art, and provides a chalcogenide phase change super-structured surface device with light field phase modulation, which improves the efficiency of phase modulation of spatial light field of the chalcogenide phase change super-structured surface device.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A chalcogenide phase change super-structured surface device with light field phase modulation comprises, from bottom to top, a dielectric substrate, a reflective layer, a dielectric isolation layer, a chalcogenide phase change microstructure and a dielectric protective layer. By adjusting the geometric parameters of the chalcogenide phase change super-structured surface device, the resonance center wavelength of the dielectric resonance mode supported by the chalcogenide phase change microstructure in the amorphous state is close to the target wavelength, the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength is reduced, and the efficiency of phase modulation of spatial light field of the chalcogenide phase change super-structured surface device is improved.

[0008] According to the above technical means, in order to improve the efficiency of phase modulation of spatial light field of the chalcogenide phase change super-structured surface, the geometric parameters of the super-structured surface unit structure are reasonably adjusted, so that the resonance center wavelength of the dielectric resonance mode supported by the chalcogenide phase change microstructure in the amorphous state is close to the target wavelength, the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength is reduced on the basis of ensuring a certain phase modulation depth, the minimum reflectivity of the chalcogenide phase change super-structured surface in the phase change process of the chalcogenide phase change material is improved, and the efficiency of phase modulation of spatial light field of the chalcogenide phase change super-structured surface is improved. The dielectric isolation layer can make the resonance mode away from the metal reflective layer and reduce the absorption of the metal reflective layer. The dielectric protective layer can protect the chalcogenide phase change microstructure, and also can play a role in making the resonance mode away from the metal reflective layer and reducing the absorption of the metal reflective layer.

[0009] Further, when a spatial light field is incident, a medium resonance mode can be excited in the chalcogenide phase-change microstructure. Due to the presence of the reflective layer, the medium resonance mode can be coupled with its mirror resonance mode. By reasonably designing the geometric parameters of the metasurface unit structure, the medium resonance mode can always be in an over-coupling state during the phase change of the chalcogenide material, and thus the chalcogenide phase-change metasurface can realize phase modulation of the reflected light field during the phase change of the chalcogenide material.

[0010] Further, the resonance center wavelength of the medium resonance mode supported by the chalcogenide phase-change microstructure gradually red shifts as the crystallization rate of the chalcogenide phase-change microstructure increases. By reasonably designing the geometric parameters of the metasurface unit structure, the resonance center wavelength of the medium resonance mode supported by the chalcogenide phase-change microstructure when the chalcogenide phase-change microstructure is in an amorphous state is close to a target wavelength, and the target wavelength is less than or equal to the resonance center wavelength of the medium resonance mode supported by the chalcogenide phase-change microstructure when the crystallization rate of the chalcogenide phase-change microstructure is 40%. On the basis of ensuring a certain phase modulation depth, the absorption of the crystallized chalcogenide phase-change microstructure at the target wavelength is reduced, the minimum reflectivity of the chalcogenide phase-change metasurface during the phase change of the chalcogenide material is improved, and thus the efficiency of the spatial light field phase modulation of the chalcogenide phase-change metasurface is improved.

[0011] Further, the geometric parameters of the chalcogenide phase-change metasurface device include a period, a longitudinal thickness of each layer, and a lateral size of the chalcogenide phase-change microstructure.

[0012] Further, the material of the dielectric substrate includes quartz glass, silicon nitride, crystal or amorphous silicon, and the thickness is greater than any selection of the target wavelength.

[0013] Further, the material of the reflective layer includes a metal material, a dielectric material or a distributed Bragg reflector. The metal material includes gold, aluminum, titanium or platinum, and the thickness is any selection that can provide high reflection for the target wavelength range. The dielectric material includes quartz glass, silicon nitride, crystal or amorphous silicon, and the thickness is any selection that can provide high reflection for the target wavelength range. The distributed Bragg reflector is composed of two thin films with different refractive indexes stacked periodically. The material of the high-refractive-index thin film includes quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon. The material of the low-refractive-index thin film includes quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon. The thickness of the two thin films is set based on the target wavelength and the distributed Bragg reflection condition, and the distributed Bragg reflector can provide high reflection for the target wavelength range. The high reflection represents a reflectivity greater than 90%.

[0014] Further, the material of the dielectric isolation layer is a dielectric material with low refractive index and low loss in the target waveband; the material of the chalcogenide phase change microstructure is a chalcogenide phase change material, including a chalcogenide phase change material with no absorption in the target waveband in different phase states, and a chalcogenide phase change material with low absorption in the amorphous state and high absorption in the crystalline state in the target waveband; and the material of the dielectric protection layer is a dielectric material with low refractive index and low loss in the target waveband.

[0015] Further, the material of the dielectric isolation layer includes aluminum oxide, silicon oxide or gallium nitride, and the thickness is less than any selected target wavelength.

[0016] Further, the material of the chalcogenide phase change microstructure is a chalcogenide phase change material, including Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3 or Sb2S3; the longitudinal thickness is less than any selected target wavelength, and the lateral size is less than any selected super-structure surface period.

[0017] Further, the material of the dielectric protection layer includes aluminum oxide, silicon oxide or gallium nitride, and the thickness is less than any selected target wavelength.

[0018] The application also provides a light field phase modulation method of the chalcogenide phase change super-structure surface device, which includes adjusting the geometric parameters of the chalcogenide phase change super-structure surface device, including the period, the longitudinal thickness of each layer, and the lateral size of the chalcogenide phase change microstructure, so that the dielectric resonance mode is always in the over-coupling state in the phase change process of the chalcogenide phase change material, and then the chalcogenide phase change super-structure surface can realize the phase modulation of the reflected light field in the phase change process of the chalcogenide phase change material, and at the same time, the resonance center wavelength of the dielectric resonance mode supported when the chalcogenide phase change microstructure is in the amorphous state is close to the target wavelength, which is less than or equal to the resonance center wavelength of the dielectric resonance mode supported when the crystallization rate of the chalcogenide phase change microstructure is 40%, on the basis of ensuring a certain phase modulation depth, the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength is reduced, the minimum reflectivity of the chalcogenide phase change super-structure surface in the phase change process of the chalcogenide phase change material is improved, and thus the efficiency of the spatial light field phase modulation of the chalcogenide phase change super-structure surface is improved.

[0019] Compared with the prior art, the beneficial effects are that the chalcogenide phase change super-structure surface device provided by the application reduces the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength on the basis of ensuring a certain phase modulation depth, improves the minimum reflectivity of the chalcogenide phase change super-structure surface in the phase change process of the chalcogenide phase change material, and thus improves the efficiency of the spatial light field phase modulation of the chalcogenide phase change super-structure surface. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of a chalcogenide phase change super-structure surface unit structure of the application.

[0021] Figure 2 is the refractive index of Ge2Sb2Se4Te1 in crystalline and amorphous state in Example 3.

[0022] Figure 3 is the extinction coefficient of Ge2Sb2Se4Te1 in crystalline and amorphous state in Example 3.

[0023] Figure 4 is the relationship between the refractive index and extinction coefficient of Ge2Sb2Se4Te1 at wavelength 1550 nm and the crystallization rate in Example 3.

[0024] Figure 5 is the reflectance spectrum of the metasurface unit in Example 3 when Ge2Sb2Se4Te1 is in crystalline and amorphous state.

[0025] Figure 6 is the phase spectrum of the metasurface unit in Example 3 when Ge2Sb2Se4Te1 is in crystalline and amorphous state.

[0026] Figure 7 is the reflectance spectrum and transmittance spectrum of the metasurface unit in Example 3 when the crystallization rate of Ge2Sb2Se4Te1 is 40%.

[0027] Figure 8 is the absolute value distribution of the electric field in zy cross-section at wavelength 1550 nm of the metasurface unit in Example 3 when the crystallization rate of Ge2Sb2Se4Te1 is 40%.

[0028] Figure 9 is the absolute value distribution of the electric field in zx cross-section at wavelength 1550 nm of the metasurface unit in Example 3 when the crystallization rate of Ge2Sb2Se4Te1 is 40%.

[0029] Figure 10 is the absolute value distribution of the electric field in yx cross-section at wavelength 1550 nm of the metasurface unit in Example 3 when the crystallization rate of Ge2Sb2Se4Te1 is 40%.

[0030] Figure 11 is the change of the real part and imaginary part of the complex amplitude of the reflected light field at wavelength 1550 nm of the metasurface unit in Example 3 during the phase transition of Ge2Sb2Se4Te1.

[0031] Figure 12 is the multipole decomposition of the metasurface unit in Example 3 when the crystallization rate of Ge2Sb2Se4Te1 is 40%.

[0032] Figure 13 is the relationship between the phase of the metasurface unit and the crystallization rate of Ge2Sb2Se4Te1 at different wavelengths in Example 3.

[0033] Figure 14 is the reflectivity of the metasurface unit in Example 3 at different wavelengths as a function of Ge2Sb2Se4Ti crystallization.

[0034] Figure 15 is the phase modulation amount of the metasurface unit in Example 3 at wavelengths 1530 nm, 1550 nm, and 1565 nm as a function of Ge2Sb2Se4Ti crystallization.

[0035] Figure 16 is the reflectivity of the metasurface unit in Example 3 at wavelengths 1530 nm, 1550 nm, and 1565 nm as a function of Ge2Sb2Se4Ti crystallization.

[0036] Figure 17 is the average reflectivity and phase modulation amount of the metasurface in Example 3 at different wavelengths.

[0037] Figure 18 is the minimum reflectivity and maximum reflectivity of the metasurface in Example 3 at different wavelengths.

[0038] Figure 19 is the normalized scattering intensity of the metasurface in Example 3 at different Ge2Sb2Se4Ti crystallization as a function of Ge2Sb2Se4Ti cylinder radius.

[0039] Figure 20 is the phase modulation amount of the metasurface in Example 3 at different wavelengths as a function of Ge2Sb2Se4Ti cylinder radius.

[0040] Figure 21 is the minimum reflectivity of the metasurface in Example 3 at different wavelengths as a function of Ge2Sb2Se4Ti cylinder radius.

[0041] Figure 22 is the maximum reflectivity of the metasurface in Example 3 at different wavelengths as a function of Ge2Sb2Se4Ti cylinder radius.

[0042] Figure 23 is the average reflectivity of the metasurface in Example 3 at different wavelengths as a function of Ge2Sb2Se4Ti cylinder radius.

[0043] Figure 24 is the phase modulation amount of the metasurface in Example 3 at wavelengths 1530 nm, 1550 nm, and 1565 nm for different Ge2Sb2Se4Ti cylinder radii.

[0044] Figure 25is the minimum reflectivity of the metasurface in Example 3 at different Ge2Sb2Se4Te1 cylinder radii at wavelengths of 1530 nm, 1550 nm, and 1565 nm.

[0045] Figure 26 is the maximum reflectivity of the metasurface in Example 3 at different Ge2Sb2Se4Te1 cylinder radii at wavelengths of 1530 nm, 1550 nm, and 1565 nm.

[0046] Figure 27 is the average reflectivity of the metasurface in Example 3 at different Ge2Sb2Se4Te1 cylinder radii at wavelengths of 1530 nm, 1550 nm, and 1565 nm.

[0047] Figure 28 is the phase gradient selection of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 260 nm.

[0048] Figure 29 is the phase gradient selection of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 360 nm.

[0049] Figure 30 is the crystallization rate distribution in the phase gradient direction of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 260 nm.

[0050] Figure 31 is the crystallization rate distribution in the phase gradient direction of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 360 nm.

[0051] Figure 32 is the normalized light intensity at different deflection angles in the phase gradient direction of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 260 nm.

[0052] Figure 33 is the normalized light intensity at different deflection angles in the phase gradient direction of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 360 nm.

[0053] Figure 34 is the +1 order deflection angle size at different wavelengths of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 260 nm.

[0054] Figure 35 is the +1 order deflection angle size at different wavelengths of the gradient phase metasurface in Example 3 at a Ge2Sb2Se4Te1 cylinder radius of 360 nm.

[0055] Figure 36 is the reflectivity of different diffraction orders of the gradient phase metasurface in Example 3 at different wavelengths when the Ge2Sb2Se4Te1 cylinder radius is 260 nm.

[0056] Figure 37 is the reflectivity of different diffraction orders of the gradient phase metasurface in Example 3 at different wavelengths when the Ge2Sb2Se4Te1 cylinder radius is 360 nm.

[0057] Figure 38 is the +1 order and total reflectivity of the gradient phase metasurface in Example 3 at wavelength 1550 nm when the Ge2Sb2Se4Te1 cylinder radius is 260 nm.

[0058] Figure 39 is the +1 order and total reflectivity of the gradient phase metasurface in Example 3 at wavelength 1550 nm when the Ge2Sb2Se4Te1 cylinder radius is 360 nm.

[0059] Figure 40 is the +1 order reflectivity of the gradient phase metasurface in Example 3 at wavelength 1550 nm at different Ge2Sb2Se4Te1 cylinder radii.

[0060] Figure 41 is the +1 order and total reflectivity of the gradient phase metasurface in Example 3 at wavelength 1550 nm when the Ge2Sb2Se4Te1 cylinder radius is 360 nm.

[0061] Figure 42 is the +1 order reflectivity of the gradient phase metasurface in Example 3 at wavelength 1550 nm at different Ge2Sb2Se4Te1 cylinder radii.

[0062] FIG. 1 is a schematic diagram of a gradient phase metasurface according to an embodiment of the present application. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. The present application will be described below in one of the embodiments with reference to the specific embodiments. The drawings are only used for illustrative description, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation on the present application; in order to better illustrate the embodiments of the present application, some components in the drawings are omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable for those skilled in the art that some well-known structures and their descriptions in the drawings can be omitted.

[0064] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for exemplary illustration, and cannot be understood as a limitation on the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances. In addition, if there is a description of "first", "second", etc. in the embodiments of the present application, the description of "first", "second", etc. is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel schemes, for example, "A and / or B" includes A scheme, or B scheme, or A and B schemes that satisfy at the same time.

[0065] Embodiment 1:

[0066] The embodiment provides a chalcogenide phase change metasurface device with light field phase modulation, which comprises, from bottom to top, a dielectric substrate 1, a reflective layer 2, a dielectric isolation layer 3, a chalcogenide phase change microstructure 4, and a dielectric protective layer 5. By adjusting the geometric parameters of the chalcogenide phase change metasurface device, the resonance center wavelength of the supported dielectric resonance mode when the chalcogenide phase change microstructure 4 is in an amorphous state is close to the target wavelength, the absorption of the chalcogenide phase change microstructure after crystallization at the target wavelength is reduced, and the spatial light field phase modulation efficiency of the chalcogenide phase change metasurface device is improved.

[0067] When the spatial light field is incident, the dielectric resonance mode can be excited in the chalcogenide phase change microstructure 4, and the dielectric resonance mode can be coupled with its mirror resonance mode. By adjusting the geometric parameters of the chalcogenide phase change metasurface device, the dielectric resonance mode is always in an over-coupling state during the phase change process of the chalcogenide phase change material. When the chalcogenide phase change microstructure 4 is in an amorphous state, the resonance center wavelength of the supported dielectric resonance mode is close to the target wavelength, and the target wavelength is less than or equal to the resonance center wavelength of the supported dielectric resonance mode when the crystallization rate of the chalcogenide phase change microstructure 4 is 40%.

[0068] When the spatial light field is incident, the medium resonance mode is excited in the chalcogenide phase transition microstructure 4. Due to the presence of the reflective layer 2, the medium resonance mode can be coupled with its mirror resonance mode. By reasonably designing the geometric parameters of the metasurface unit structure, including the period, the longitudinal thickness of each layer, and the lateral size of the chalcogenide phase transition microstructure 4, the medium resonance mode can always be in an over-coupling state during the phase transition of the chalcogenide material, and the chalcogenide phase transition metasurface can realize phase modulation of the reflected light field during the phase transition of the chalcogenide material. The medium isolation layer 3 can make the resonance mode away from the metal reflective layer 2, and reduce the absorption of the metal reflective layer 2. The medium protective layer 5 can protect the chalcogenide phase transition microstructure 4, and also can play a role in making the resonance mode away from the metal reflective layer 2 and reducing the absorption of the metal reflective layer 2.

[0069] In order to improve the efficiency of spatial light field phase modulation of the chalcogenide phase transition metasurface, the geometric parameters of the metasurface unit structure are reasonably adjusted, including the period, the longitudinal thickness of each layer, and the lateral size of the chalcogenide phase transition microstructure 4. When the chalcogenide phase transition microstructure 4 is in an amorphous state, the resonance center wavelength of the supported medium resonance mode is close to the target wavelength, and the target wavelength is less than or equal to the resonance center wavelength of the supported medium resonance mode when the crystallization rate of the chalcogenide phase transition microstructure 4 is 40%. On the basis of ensuring a certain phase modulation depth, the absorption of the crystallized chalcogenide phase transition microstructure at the target wavelength is reduced, the minimum reflectivity of the chalcogenide phase transition metasurface during the phase transition of the chalcogenide material is improved, and the efficiency of spatial light field phase modulation of the chalcogenide phase transition metasurface is improved.

[0070] In the embodiment, the material of the medium substrate 1 includes quartz glass, silicon nitride, crystal or amorphous silicon, and the thickness is greater than any selected target wavelength, and the flat plate structure.

[0071] The material of the reflective layer 2 includes a metal material, a dielectric material or a distributed Bragg reflector. The metal material includes gold, aluminum, titanium or platinum, and the thickness is any selected value that can provide high reflection for the target wavelength range. The dielectric material includes quartz glass, silicon nitride, crystal or amorphous silicon, and the thickness is any selected value that can provide high reflection for the target wavelength range. The distributed Bragg reflector is composed of two kinds of thin films with different refractive indexes stacked periodically. The material of the high refractive index thin film includes quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon. The material of the low refractive index thin film includes quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon. The thickness of the two kinds of thin films is set based on the target wavelength and the distributed Bragg reflection condition, and the distributed Bragg reflector can provide high reflection for the target wavelength range. The high reflection means a reflectivity greater than 90%.

[0072] The material of the dielectric isolation layer 3 is a dielectric material with low refractive index and low loss in the target wavelength band, including aluminum oxide, silicon oxide or gallium nitride, and the thickness is less than any selected target wavelength.

[0073] The material of the chalcogenide phase change microstructure 4 is a chalcogenide phase change material, including a chalcogenide phase change material with no absorption in the target wavelength band in different phases, and a chalcogenide phase change material with low absorption in amorphous state and high absorption in crystalline state in the target wavelength band; including Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3 or Sb2S3; the longitudinal thickness is less than any selected target wavelength, and the lateral size is less than any selected superstructure period.

[0074] The material of the dielectric protection layer 5 is a dielectric material with low refractive index and low loss in the target wavelength band, including aluminum oxide, silicon oxide or gallium nitride, and the thickness is less than any selected target wavelength.

[0075] Embodiment 2:

[0076] The embodiment provides a light field phase modulation method of a chalcogenide phase change superstructure device, including adjusting the geometric parameters of the chalcogenide phase change superstructure device, including the period, the longitudinal thickness of each layer, and the lateral size of the chalcogenide phase change microstructure, so that the dielectric resonance mode is always in an over-coupling state in the phase change process of the chalcogenide phase change material, and then the chalcogenide phase change superstructure can realize phase modulation of the reflected light field in the phase change process of the chalcogenide phase change material, and at the same time, the resonance center wavelength of the dielectric resonance mode supported when the chalcogenide phase change microstructure 4 is in amorphous state is close to the target wavelength, on the basis of ensuring a certain phase modulation depth, the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength is reduced, the minimum reflectivity of the chalcogenide phase change superstructure in the phase change process of the chalcogenide phase change material is improved, and therefore the efficiency of spatial light field phase modulation of the chalcogenide phase change superstructure is improved.

[0077] When the spatial light field is incident, the dielectric resonance mode can be excited in the chalcogenide phase change microstructure 4. Due to the existence of the reflection layer 2, the dielectric resonance mode can be coupled with the mirror image resonance mode. Reasonable design of the geometric parameters of the superstructure unit structure can make the dielectric resonance mode always in an over-coupling state in the phase change process of the chalcogenide phase change material, and then the chalcogenide phase change superstructure can realize phase modulation of the reflected light field in the phase change process of the chalcogenide phase change material.

[0078] The resonance center wavelength of the medium resonance mode supported by the chalcogenide phase change microstructure 4 gradually red shifts with the increase of the crystallization rate of the chalcogenide phase change microstructure 4. The geometric parameters of the super-structured surface unit structure are reasonably designed, so that the resonance center wavelength of the medium resonance mode supported when the chalcogenide phase change microstructure 4 is in an amorphous state is close to a target wavelength, the target wavelength is less than or equal to the resonance center wavelength of the medium resonance mode supported when the crystallization rate of the chalcogenide phase change microstructure 4 is 40%, and on the basis of ensuring a certain phase modulation depth, the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength is reduced, the minimum reflectivity of the chalcogenide phase change super-structured surface in the phase change process of the chalcogenide phase change material is improved, and thus the efficiency of the spatial light field phase modulation of the chalcogenide phase change super-structured surface is improved.

[0079] The geometric parameters of the super-structured surface unit structure, including the period, the longitudinal thickness of each layer, and the lateral size of the chalcogenide phase change microstructure, are reasonably designed.

[0080] In this embodiment, by reasonably adjusting the geometric parameters of the super-structured surface unit structure, including the period, the longitudinal thickness of each layer, and the lateral size of the chalcogenide phase change microstructure 4, the resonance center wavelength of the medium resonance mode supported when the chalcogenide phase change microstructure is in an amorphous state is close to a target wavelength, the target wavelength is less than or equal to the resonance center wavelength of the medium resonance mode supported when the crystallization rate of the chalcogenide phase change microstructure 4 is 40%, and on the basis of ensuring a certain phase modulation depth, the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength is reduced, the minimum reflectivity of the chalcogenide phase change super-structured surface in the phase change process of the chalcogenide phase change material is improved, and thus the efficiency of the spatial light field phase modulation of the chalcogenide phase change super-structured surface is improved.

[0081] Embodiment 3:

[0082] In this embodiment, a chalcogenide phase change super-structured surface device with high-efficiency light field phase modulation capability is provided, and the designed super-structured surface unit structure is sequentially arranged from bottom to top as follows: a crystal Si substrate, an Au reflection layer, an Al2O3 isolation layer, a Ge2Sb2Se4Te1 cylinder, and an Al2O3 protective layer.

[0083] The optical properties of the designed metasurface are simulated by the commercial software Lumerical FDTD, and the multipole decomposition of the metasurface is simulated by the commercial software COMSOL Multiphysics. In the simulation model, the radius and thickness of the Ge2Sb2Se4Te1 cylinder are 360 nm and 60 nm, respectively, the thickness of the Au reflective layer is 100 nm, the thickness of the Al2O3 isolation layer is 50 nm, the thickness of the Al2O3 protective layer is 20 nm, the thickness of the crystal Si substrate is 500 μm, the period of the metasurface is set to 1150 nm, and the target waveband is the C waveband (1530 nm-1565 nm). The x and y directions of the metasurface unit are set as periodic boundary conditions to simulate the real periodic structure of the metasurface. The top and bottom of the metasurface unit are set as perfect matched layers to simulate the real infinite isotropic medium environment.

[0084] In terms of complex refractive index of materials, the complex refractive index of Si, Au and Al2O3 is derived from the material database in the commercial software Lumerical FDTD, and the complex refractive index of Ge2Sb2Se4Te1 material is derived from literature reports. The extinction coefficient of amorphous Ge2Sb2Se4Te1 material is close to zero in the near-infrared waveband, but the extinction coefficient of its crystal state in the near-infrared waveband is still not negligible, and its extinction coefficient gradually increases with the increase of crystallization rate. Figure 2 and Figure 3 The refractive index and extinction coefficient of Ge2Sb2Se4Te1 crystal and amorphous state are shown, respectively. Figure 4 The relationship diagram of the refractive index and extinction coefficient of Ge2Sb2Se4Te1 at a wavelength of 1550 nm and the crystallization rate is shown. From Figure 2 , Figure 3 and Figure 4 , it can be seen that the extinction coefficient of Ge2Sb2Se4Te1 gradually increases with the increase of the crystallization rate, and the extinction coefficient reaches the maximum in the completely crystalline state. The refractive index and extinction coefficient of the intermediate state of Ge2Sb2Se4Te1 are calculated by the Lorentz-Lorenz formula, and the Lorentz-Lorenz formula is as follows:

[0085]

[0086] wherein ∈ c (λ) and ∈ a (λ) are the complex dielectric constant of the crystal and amorphous state at the wavelength λ, respectively, m is the crystallization rate, and ∈ eff (λ) is the effective complex dielectric constant when the crystallization rate is m.

[0087] When the spatial light field is incident, an electric dipole (ED) dominant dielectric resonant mode can be excited in the Ge2Sb2Se4Te1 cylinder. Due to the existence of the Au reflective layer, the ED resonant mode can couple with its mirror image ED resonant mode. By reasonably designing the geometric parameters of the super-structured surface unit structure, including the period, the longitudinal thickness of each layer and the lateral size of the chalcogenide phase transition microstructure, the resonant mode can always be in the over-coupling state in the phase transition process of Ge2Sb2Se4Te1, and then the super-structured surface can realize the phase modulation of the reflected light field in the phase transition process of Ge2Sb2Se4Te1. Figure 5 and Figure 6 The reflection spectrum and phase spectrum of the super-structured surface unit when Ge2Sb2Se4Te1 is in the crystalline state and amorphous state, respectively, can be seen that the resonant mode is always in the over-coupling state in the phase transition process of Ge2Sb2Se4Te1, and with the increase of the crystallization rate, the resonant peak gradually red shifts, and the phase modulation of the reflected light field can be realized in the phase transition process of Ge2Sb2Se4Te1.

[0088] Figure 7 The reflection spectrum and transmission spectrum of the super-structured surface unit when the crystallization rate of Ge2Sb2Se4Te1 is 40% can be seen that there is a resonant peak at a wavelength of 1550 nm. In order to characterize the excited resonant mode, the absolute value distribution of the electric field of the super-structured surface unit at a wavelength of 1550 nm when the crystallization rate of Ge2Sb2Se4Te1 is 40% in the zy, zx and yx cross sections is simulated, as shown in Figure 8 , Figure 9 and Figure 10 The absolute value distribution of the electric field is a typical ED dominant dielectric resonant mode. Figure 11 The variation diagram of the real part and imaginary part of the complex amplitude of the reflected light field of the super-structured surface unit in the phase transition process of Ge2Sb2Se4Te1 at a wavelength of 1550 nm can be seen that the resonant mode is in the over-coupling state.

[0089] In order to further characterize the excited resonant mode, the super-structured surface unit when the crystallization rate of Ge2Sb2Se4Te1 is 40% is subjected to multipole decomposition, as shown in Figure 12 From the multipole decomposition diagram, it can be seen that the resonant mode of the super-structured surface unit when the crystallization rate of Ge2Sb2Se4Te1 is 40% at a wavelength of 1550 nm is an ED resonant mode dominant, and other resonant modes have very weak contribution to the scattering cross section of the super-structured surface unit.

[0090] In order to show the optical properties of the super-structured surface unit, the phase and reflectivity of the super-structured surface unit under different wavelengths and the relationship with the crystallization rate of Ge2Sb2Se4Te1 are simulated, as shown in Figure 13 and Figure 14The existence of ED resonance mode and the phase modulation of reflected light field in the phase transition process of Ge2Sb2Se4Te1 can be obviously seen from the figure. Figure 15 and Figure 16 are the phase modulation amount and reflectivity of the metasurface unit at wavelengths 1530 nm, 1550 nm and 1565 nm, respectively, and the relationship diagram of the crystallization rate of Ge2Sb2Se4Te1. Figure 17 is the average reflectivity and phase modulation amount of the metasurface at different wavelengths in the phase transition process of Ge2Sb2Se4Te1. Figure 18 is the minimum reflectivity and maximum reflectivity of the metasurface at different wavelengths in the phase transition process of Ge2Sb2Se4Te1. It can be seen that in the range of C band, in the phase transition process of Ge2Sb2Se4Te1, the metasurface always maintains a minimum reflectivity greater than 28%, a maximum reflectivity greater than 92%, an average reflectivity greater than 58%, and a phase modulation depth greater than 260°.

[0091] By reasonably adjusting the geometric parameters of the metasurface unit structure, including the period, the longitudinal thickness of each layer and the lateral size of the chalcogenide phase transition microstructure, etc., the resonance center wavelength of the supported dielectric resonance mode when the chalcogenide phase transition microstructure is in amorphous state is close to the target wavelength. Here, the change of Ge2Sb2Se4Te1 cylinder radius is taken as an example to demonstrate this idea. Figure 19 is the normalized scattering intensity at different crystallization rates of different Ge2Sb2Se4Te1 cylinder radii. With the increase of Ge2Sb2Se4Te1 cylinder radius, the normalized scattering intensity peak gradually moves to the amorphous state with smaller extinction coefficient, which indicates that with the increase of Ge2Sb2Se4Te1 cylinder radius, the resonance center wavelength of the supported dielectric resonance mode when the chalcogenide phase transition microstructure is in amorphous state gradually approaches the target wavelength.

[0092] Figure 20 , Figure 21 , Figure 22 and Figure 23 are the minimum reflectivity, maximum reflectivity, average reflectivity and phase modulation amount at different wavelengths of different Ge2Sb2Se4Te1 cylinder radii. Figure 24 , Figure 25 , Figure 26 and Figure 27The minimum reflectivity, the maximum reflectivity, the average reflectivity and the phase modulation amount of different Ge2Sb2Se4Te1 cylinder radius at wavelengths 1530 nm, 1550 nm and 1565 nm, respectively. It can be seen that with the increase of the Ge2Sb2Se4Te1 cylinder radius, the minimum reflectivity of the chalcogenide phase transition metasurface unit structure in the phase transition process of the chalcogenide phase transition material gradually increases, while a certain phase modulation depth can be ensured, and the maximum reflectivity and the average reflectivity change little.

[0093] In order to show that the efficiency of spatial light field phase modulation of the metasurface can be improved based on this idea, a gradient phase metasurface is designed to realize beam deflection. A period of gradient phase metasurface is composed of 12 metasurface units, every 4 metasurface units is a group, the phase is 3 orders, that is, 0°, 120° and 240°, the gradient phase metasurface only exists in one direction of phase gradient, and there is no phase gradient in the direction perpendicular to the direction, the polarization direction of the incident light is parallel to the phase gradient direction, and the target wavelength is 1550 nm. The optical properties of the designed gradient phase metasurface are simulated by using the commercial software Lumerical FDTD, and the x and y directions of the gradient phase metasurface are set as periodic boundary conditions to simulate the real gradient phase metasurface periodic structure. The top and bottom of the gradient phase metasurface are set as perfect matched layer to simulate the real infinite isotropic medium environment.

[0094] Figure 28 and Figure 29 are the multipole decomposition of the metasurface at wavelengths 1550 nm when the Ge2Sb2Se4Te1 cylinder radius is 260 nm and 360 nm, respectively. When the Ge2Sb2Se4Te1 cylinder radius is 260 nm, the normalized scattering intensity peak of the metasurface at wavelength 1550 nm is located at 72% crystallization rate. When the Ge2Sb2Se4Te1 cylinder radius is 360 nm, the normalized scattering intensity peak of the metasurface at wavelength 1550 nm is located at 29.5% crystallization rate.

[0095] Figure 30 and Figure 31 are the phase gradients when the Ge2Sb2Se4Te1 cylinder radius is 260 nm and 360 nm, respectively. Figure 32 and Figure 33 are the crystallization rate distributions in the phase gradient direction when the Ge2Sb2Se4Te1 cylinder radius is 260 nm and 360 nm, respectively. According to the generalized Snell law, this gradient phase metasurface can realize a deflection angle of about 6.45° in the phase gradient direction for the reflected light, and the generalized Snell law is as follows:

[0096]

[0097] where θi is the incident angle, θf is the deflection angle, λ0 is the target wavelength, i r i is the incident medium environment refractive index.

[0098] Figure 34 and Figure 35 are the normalized light intensity at different deflection angles in the direction of phase gradient when the radius of Ge2Sb2Se4Te1 cylinder is 260 nm and 360 nm, respectively. Figure 36 Figure 37 are the +1 order deflection angles at different wavelengths when the radius of Ge2Sb2Se4Te1 cylinder is 260 nm and 360 nm, respectively. It can be seen that the gradient phase metasurface can realize a deflection angle of about 6.45° for reflected light, which meets the generalized Snell's law.

[0099] In order to show the efficiency of spatial light field phase modulation, the reflectivity distribution of different diffraction orders at different wavelengths when the radius of Ge2Sb2Se4Te1 cylinder is 260 nm and 360 nm is simulated, as shown in Figure 38 Figure 39 It can be seen that the diffraction energy is mainly distributed in the 0 and +1 order diffraction orders. Figure 40 Figure 41 are the +1 order and total reflectivity at wavelength 1550 nm when the radius of Ge2Sb2Se4Te1 cylinder is 260 nm and 360 nm, respectively, Figure 42 is the +1 order reflectivity at wavelength 1550 nm for different Ge2Sb2Se4Te1 cylinder radii. It can be seen that with the increase of the radius of Ge2Sb2Se4Te1 cylinder, the +1 order reflectivity gradually rises under the condition of the same target wavelength and the same gradient phase, which shows that by reasonably adjusting the geometric parameters of the metasurface unit structure, including the period, the longitudinal thickness of each layer and the lateral size of the chalcogenide phase transition microstructure, etc., the resonance center wavelength of the supported medium resonance mode when the chalcogenide phase transition microstructure is in amorphous state is close to the target wavelength. On the basis of ensuring a certain phase modulation depth, the absorption of the chalcogenide phase transition microstructure after crystallization at the target wavelength can be reduced, the minimum reflectivity of the chalcogenide phase transition metasurface unit structure in the phase transition process of the chalcogenide phase transition material can be improved, and thus the efficiency of spatial light field phase modulation of the device can be improved.

[0100] ​​​​​​In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction, and the combination is within the scope of the present application.

[0101] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation manner of the present application. Based on the above description, those skilled in the art can make other different forms of changes or variations. Here, it is not necessary and impossible to enumerate all the implementation manners. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A chalcogenide phase transition metasurface device with optical field phase modulation, characterized in that, From bottom to top, it includes: a dielectric substrate (1), a reflective layer (2), a dielectric isolation layer (3), a chalcogenide phase change microstructure (4), and a dielectric protective layer (5); the material of the chalcogenide phase change microstructure (4) is a chalcogenide phase change material; by adjusting the geometric parameters of the chalcogenide phase change metasurface device, the dielectric resonance mode is always in an overcoupled state during the phase change process of the chalcogenide phase change material, and the resonance center wavelength of the dielectric resonance mode supported by the chalcogenide phase change microstructure (4) when it is amorphous is close to the target wavelength, thereby reducing the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength, so as to improve the chalcogenide phase change metasurface device. The spatial optical field phase modulation efficiency of the surface device; the resonant center wavelength of the dielectric resonance mode supported by the chalcogenide phase transition microstructure (4) gradually redshifts as the crystallinity of the chalcogenide phase transition microstructure (4) increases; the dielectric isolation layer (3) moves the resonance mode away from the reflective layer (2) to reduce the absorption of the reflective layer (2); the dielectric protection layer (5) protects the chalcogenide phase transition microstructure (4) from the reflective layer (2) to reduce the absorption of the reflective layer (2); the geometric parameters include the period, the longitudinal thickness of each layer, and the transverse dimension of the chalcogenide phase transition microstructure (4).

2. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 1, characterized in that, When a spatial light field is incident, a medium resonance mode can be excited in the sulfide phase change microstructure (4), and the medium resonance mode can be coupled with its mirror resonance mode; by adjusting the geometric parameters of the sulfide phase change metasurface device.

3. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 2, characterized in that, By adjusting the geometric parameters of the sulfide phase change metasurface device, the resonance center wavelength of the dielectric resonance mode supported by the sulfide phase change microstructure (4) when it is amorphous is made close to the target wavelength, and the target wavelength is less than or equal to the resonance center wavelength of the dielectric resonance mode supported by the sulfide phase change microstructure (4) when its crystallinity is 40%.

4. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 3, characterized in that, The dielectric substrate (1) is made of quartz glass, silicon nitride, crystalline or amorphous silicon, and has a thickness greater than the target wavelength of any of the following choices.

5. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 3, characterized in that, The material of the reflective layer (2) includes a metallic material, a dielectric material, or a distributed Bragg reflector; the metallic material includes gold, aluminum, titanium, or platinum, and the thickness is any choice that can provide high reflection for the target wavelength; the dielectric material includes quartz glass, silicon nitride, crystalline or amorphous silicon, and the thickness is any choice that can provide high reflection for the target wavelength; the distributed Bragg reflector is composed of two thin films with different refractive indices stacked periodically, the high refractive index thin film is made of quartz glass, alumina, silicon nitride, crystalline or amorphous silicon, and the low refractive index thin film is made of quartz glass, alumina, silicon nitride, crystalline or amorphous silicon, the thickness of both films is set based on the target wavelength and the distributed Bragg reflection conditions, and the distributed Bragg reflector can provide high reflection for the target wavelength; wherein high reflection means a reflectivity greater than 90%.

6. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 3, characterized in that, The dielectric isolation layer (3) is made of a dielectric material with low refractive index and low loss in the target wavelength band; the sulfide phase change microstructure (4) is made of a sulfide phase change material, including sulfide phase change materials that have no absorption in the target wavelength band under different phase states, and sulfide phase change materials with low absorption in the amorphous state and high absorption in the crystalline state under the target wavelength band; the dielectric protective layer (5) is made of a dielectric material with low refractive index and low loss in the target wavelength band.

7. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 6, characterized in that, The dielectric isolation layer (3) is made of aluminum oxide, silicon oxide or gallium nitride, and its thickness is any choice less than the target wavelength.

8. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 6, characterized in that, The materials of the sulfur-based phase change microstructure (4) include Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3 or Sb2S3; the longitudinal thickness is any choice less than the target wavelength, and the transverse dimension is any choice less than the metasurface period.

9. The chalcogenide phase transition metasurface device with optical field phase modulation according to claim 6, characterized in that, The material of the dielectric protective layer (5) includes aluminum oxide, silicon oxide or gallium nitride, and the thickness is any choice less than the target wavelength.

10. A method for optical field phase modulation of a chalcogenide phase change metasurface device according to any one of claims 1 to 9, comprising adjusting the geometric parameters of the chalcogenide phase change metasurface device, including the period, the longitudinal thickness of each layer, and the transverse dimension of the chalcogenide phase change microstructure (4), so that the dielectric resonance mode is always in an overcoupled state during the phase change process of the chalcogenide phase change material, thereby enabling the surface of the chalcogenide phase change microstructure (4) to achieve phase modulation of the reflected light field during the phase change process of the chalcogenide phase change material, and simultaneously making the resonance center wavelength of the dielectric resonance mode supported when the chalcogenide phase change microstructure (4) is amorphous close to the target wavelength, wherein the target wavelength is less than or equal to the resonance center wavelength of the dielectric resonance mode supported when the crystallinity of the chalcogenide phase change microstructure (4) is 40%, thereby reducing the absorption of the crystallized chalcogenide phase change microstructure at the target wavelength while ensuring a certain phase modulation depth, increasing the minimum reflectivity of the chalcogenide phase change metasurface during the phase change process of the chalcogenide phase change material, thereby improving the efficiency of spatial optical field phase modulation of the chalcogenide phase change metasurface.

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