A spatial light field phase modulation device based on chalcogenide phase change FP resonant cavity and its preparation method

Abstract

The present invention relates to a spatial light field phase modulation device and method based on a sulfur-based phase change F-P resonant cavity. The phase modulation device includes, from bottom to top, a dielectric substrate, a reflective layer, a dielectric resonance wavelength adjustment layer, a sulfur-based phase change active layer, and a distributed Bragg reflector. Since the refractive index contrast of the sulfur-based phase change material during the phase change process is relatively large, the dielectric resonance wavelength adjustment layer can be used to replace part of the sulfur-based phase change active layer, compressing the thickness of the sulfur-based phase change active layer as the active material, thereby reducing the driving power consumption of the device and improving the modulation rate of the device; the preparation process flow during modulation provided by the present invention only involves thin film growth, and does not involve the processing technology of micro-nano structures, and the preparation process is relatively simple.

Description

Technical Field

[0001] The present invention relates to the field of light field control technology, and more specifically, to a spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity and a preparation method thereof. Background Art

[0002] With the rapid development of modern optical technology, multi-dimensional control of spatial light fields has become an extremely attractive and challenging problem in the field of optics. Its research content mainly includes the control of parameters such as phase, amplitude, coherence and polarization state of light fields. Traditional spatial light modulators mainly include liquid crystal spatial light modulators and micro-electromechanical systems. Liquid crystal spatial light modulators are a device that uses the electro-optical effect of liquid crystal molecules to achieve spatial light field control. It has the advantages of many pixels and flexible control. Micro-electromechanical systems, or micro-electromechanical systems, refer to independent intelligent systems with internal structures at the micron or even nanometer level. Digital micromirror devices are common micro-electromechanical systems for spatial light field control. They are a structural array composed of multiple high-speed digital optical reflective switches, and each optical reflective switch can be regarded as a pixel. Although traditional spatial light modulators have the advantages of high resolution, strong programmability, high diffraction efficiency and large fill factor, they generally have large pixels, which makes the spatial light modulator bulky and difficult to achieve large-scale high-density integration on chip, thus failing to meet the needs of high-density integrated optoelectronic systems in consumer electronics, medical testing, aerospace and other fields. In addition, they usually require larger driving voltage or current, resulting in higher device power consumption and lower modulation rate.

[0003] In recent years, the emergence of metasurfaces has provided a new idea for large-scale, high-density integrated optoelectronic systems, and has attracted widespread attention from scholars at home and abroad. The spatial light field control characteristics of metasurfaces are determined by the geometric parameters of the metasurface units and the complex dielectric constant of the materials. Therefore, once the metasurface is designed and prepared, its functional characteristics are fixed and cannot be actively tuned, and it cannot meet the needs of application scenarios such as dynamic phase modulation, zoom imaging, and dynamic beam deflection. With the development of spatial light modulation technology, people have realized the functional limitations of static metasurfaces, and thus began to study dynamically controllable active metasurfaces. The core idea of ​​active metasurfaces is to combine static metasurfaces with active materials, and stimulate active materials and change various properties of active materials through external conditions such as electricity, heat, light, mechanical stretching, and micro-electromechanical systems, so that static metasurfaces have adjustable and reconfigurable characteristics. The emergence of actively controllable metasurfaces has greatly enhanced the flexibility of metasurface devices and expanded their application scenarios.

[0004] Sulfur-based phase change materials, represented by Ge2Sb2Te5 (GST), which undergo crystalline-amorphous transitions, are widely used as active materials to control various integrated optoelectronic devices at high speed due to their significant changes in optical, electrical and thermal properties during the phase change process. They have the advantages of fast phase change speed, low phase change power consumption, high number of cycles, no static power consumption, non-volatility and compatibility with CMOS processes. They are very suitable for use as active materials in active metasurface devices to achieve high-efficiency spatial light field phase modulation. However, the micro-nano processing process involved in preparing the micro-nano structure of the spatial light field phase modulation device based on the active metasurface is relatively complex, costly and difficult, and the active material layer in the spatial light field phase modulation device based on the active metasurface is often thicker, resulting in higher driving power consumption and lower modulation rate of the device. Summary of the invention

[0005] In order to overcome the defects in the above-mentioned prior art, the present invention provides a spatial light field phase modulation device and method based on a sulfur-based phase change FP resonant cavity. The provided phase modulation device effectively reduces the driving efficiency of the device and improves the modulation rate of the device; the provided method for preparing the phase modulation device has a simpler process flow.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity comprises, from bottom to top, a dielectric substrate, a reflection layer, a dielectric resonance wavelength adjustment layer, a chalcogenide phase change active layer, and a distributed Bragg reflector; the reflection layer provides a function of reflecting the spatial light field, the distributed Bragg reflector provides a semi-reflective and semi-transmissive function, and serves as a cavity medium of the FP resonant cavity; the chalcogenide phase change active layer serves as the cavity medium of the FP resonant cavity; wherein the dielectric resonance wavelength adjustment layer is used to replace part of the chalcogenide phase change active layer to compress the thickness of the chalcogenide phase change active layer.

[0008] According to the above technical means, when a spatial light field is incident, the metal reflective layer in the sulfur-based phase change FP resonant cavity provides the function of reflecting the spatial light field. The distributed Bragg reflector, on the one hand, provides a semi-reflective and semi-transmissive effect, and on the other hand, acts as the cavity medium of the FP resonant cavity. When the incident spatial light field meets the resonance condition of the FP cavity, resonance will be formed in the FP resonant cavity. The sulfur-based phase change active layer acts as the cavity medium of the FP cavity, and the resonance peak is displaced by virtue of the significant refractive index contrast brought about by the phase change process, thereby realizing the modulation of the phase of the reflected light field within the target band. Since the refractive index contrast of the sulfur-based phase change material during the phase change process is large, part of the sulfur-based phase change active layer can be replaced by a dielectric resonance wavelength adjustment layer, and the thickness of the sulfur-based phase change active layer as the active material can be compressed, thereby reducing the driving power consumption of the device and improving the modulation rate of the device.

[0009] Furthermore, the dielectric substrate is made of a dielectric material with low absorption in the target wavelength band, including silicon oxide, silicon nitride, crystalline silicon or amorphous silicon. The dielectric substrate thickness is any choice much greater than the target wavelength, and has a flat plate structure.

[0010] Further, the material of the reflective layer is a metal material that can provide high reflection for the target band, including gold, aluminum, titanium or platinum. The thickness of the reflective layer is any choice that can provide high reflection for the target band, a thin film structure, wherein high reflection means a reflectivity greater than 90%.

[0011] Further, the material of the dielectric resonance wavelength adjustment layer is a dielectric material with low absorption in the target band, including crystalline silicon, amorphous silicon, aluminum oxide, silicon oxide or gallium nitride. The dielectric resonance wavelength adjustment layer has a thickness less than the target wavelength, and has a thin film structure.

[0012] Further, the material of the chalcogenide phase change active layer is a chalcogenide phase change material, including Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3 or Sb2S3. The thickness of the chalcogenide phase change active layer is any one of the options less than the target wavelength, and has a thin film structure.

[0013] Furthermore, the distributed Bragg reflector is composed of two films with different refractive indices that are periodically stacked alternately; wherein the material of the high refractive index film includes chalcogenide phase change material, quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon, and the material of the low refractive index film includes quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon; the thickness of the two films are set based on the target wavelength and the distributed Bragg reflection conditions.

[0014] Furthermore, when the target band is 1530nm~1565nm, the material of the dielectric substrate is a crystalline Si substrate with a thickness of 400μm~600μm; the material of the reflective layer is gold with a thickness of 90nm~110nm; the material of the dielectric resonance wavelength adjustment layer is amorphous Si with a thickness of 20nm~40nm; the material of the sulfide phase change active layer is Sb2Se3 with a thickness of 40nm~60nm; the distributed Bragg reflector is a single-period distributed Bragg reflector composed of an Al2O3 layer and an amorphous Si layer alternately and periodically stacked, and the thicknesses of the Al2O3 layer and the amorphous Si layer are 220nm~245nm and 115nm~135nm, respectively.

[0015] The present invention also provides a method for preparing a spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity, comprising the following steps:

[0016] S1. Vapor-depositing a metal film on a dielectric substrate as a metal reflective layer;

[0017] S2. depositing an amorphous Si film on the metal reflective layer as a dielectric resonance wavelength adjustment layer;

[0018] S3. growing a chalcogenide phase change film on the dielectric resonance wavelength adjustment layer as a chalcogenide phase change active layer; annealing the chalcogenide phase change film to fully crystallize it;

[0019] S4. Fabricating a distributed Bragg reflector on the chalcogenide phase change active layer;

[0020] The metal reflective layer provides a function of reflecting the spatial light field, the distributed Bragg reflector provides a semi-reflective and semi-transmissive effect, and at the same time serves as a cavity medium of the FP resonant cavity; the sulfide phase change active layer serves as the cavity medium of the FP resonant cavity; wherein, the medium resonance wavelength adjustment layer is used to replace part of the sulfide phase change active layer to compress the thickness of the sulfide phase change active layer.

[0021] According to the above technical means, the present invention provides a method for preparing a spatial light field phase modulation device based on a sulfur-based phase change FP resonant cavity. Compared with the spatial light field phase modulation device based on an active metasurface, the process flow for preparing the proposed high-efficiency spatial light field phase modulation device based on a sulfur-based phase change FP resonant cavity only involves thin film growth and does not involve the processing technology of micro-nano structures. The preparation process is relatively simple, the cost is low, and the difficulty is relatively low.

[0022] Compared with the spatial light field phase modulation device based on liquid crystal FP resonant cavity, the active material of the proposed high-efficiency spatial light field phase modulation device based on sulfur-based phase change FP resonant cavity is sulfur-based phase change material. The refractive index contrast of sulfur-based phase change material during the phase change process is greater than the refractive index contrast brought by the electro-optical effect of liquid crystal material. Therefore, at the same target wavelength, the sulfur-based phase change active layer is thinner than the liquid crystal material layer, which can reduce the driving power consumption of the device and improve the modulation rate of the device.

[0023] Furthermore, in step S1, a metal film is evaporated by electron beam evaporation; in step S2, an amorphous Si film is deposited on the metal film by an inductively coupled plasma enhanced chemical vapor deposition system; in step S3, a chalcogenide phase change film is grown on the amorphous Si film by a thermal evaporation system; in step S4, a layer of Al2O3 film is sputtered on the chalcogenide phase change film by a magnetron sputtering method, and a layer of amorphous Si film is deposited on the Al2O3 film by an inductively coupled plasma enhanced chemical vapor deposition system, and the Al2O3 film and the amorphous Si film are alternately and periodically stacked to form a single-period distributed Bragg reflector.

[0024] Furthermore, when the target band is 1530nm~1565nm, the dielectric substrate is a crystalline Si substrate with a thickness of 400μm~600μm; the reflective layer is a gold reflective layer with a thickness of 90nm~110nm; the material of the dielectric resonance wavelength adjustment layer is amorphous Si with a thickness of 20nm~40nm; the material of the sulfur-based phase change active layer is Sb2Se3 with a thickness of 40nm~60nm; the thickness of the Al2O3 film is 220nm~245nm; the thickness of the amorphous Si film is 115nm~135nm.

[0025] Compared with the prior art, the beneficial effects are:

[0026] 1. Compared with the spatial light field phase modulation device based on active metasurface, the process flow of preparing the high-efficiency spatial light field phase modulation device based on chalcogenide phase change FP resonant cavity only involves thin film growth, and does not involve the processing technology of micro-nano structure. The preparation process is relatively simple, the cost is low, and the difficulty is relatively small;

[0027] 2. Compared with the spatial light field phase modulation device based on liquid crystal FP resonant cavity, the active material of the high-efficiency spatial light field phase modulation device based on sulfur-based phase change FP resonant cavity proposed in the present invention is sulfur-based phase change material. The refractive index contrast of sulfur-based phase change material in the phase change process is greater than the refractive index contrast brought by the electro-optical effect of liquid crystal material. Therefore, at the same target wavelength, the sulfur-based phase change active layer is thinner than the liquid crystal material layer, thereby reducing the driving power consumption of the device and improving the modulation rate of the device.

[0028] 3. Compared with the common spatial light field phase modulation device based on sulfur-based phase change FP resonant cavity, the high-efficiency spatial light field phase modulation device based on sulfur-based phase change FP resonant cavity proposed in the present invention replaces part of the sulfur-based phase change material with other dielectric materials, compresses the thickness of the sulfur-based phase change material layer as the active material, thereby further reducing the driving power consumption of the device and improving the modulation rate of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of Example 2.

[0030] Figure 2 is the refractive index of Sb2Se3 in crystalline and amorphous states.

[0031] Figure 3 is the extinction coefficient of Sb2Se3 crystalline and amorphous states.

[0032] Figure 4 This is the relationship between the refractive index, extinction coefficient and crystallization rate of Sb2Se3 material at a wavelength of 1550nm.

[0033] Figure 5 These are the reflection and transmission spectra of the phase-change FP cavity when the crystallization rate of Sb2Se3 is 59.5%.

[0034] Figure 6 It is the absolute value distribution of the electric field in the longitudinal section of the chalcogenide phase change FP resonant cavity at a wavelength of 1550nm when the crystallization rate of Sb2Se3 is 59.5%.

[0035] Figure 7 It is the relationship between the phase of the sulfur-based phase-change FP resonant cavity at different wavelengths and the crystallization rate of Sb2Se3.

[0036] Figure 8 It is the relationship between the reflectivity of the sulfur-based phase-change FP resonant cavity at different wavelengths and the crystallization rate of Sb2Se3.

[0037] Fig. 9 It is the relationship between the phase modulation amount of the sulfur-based phase change FP resonant cavity at wavelengths of 1530nm, 1550nm and 1565nm and the crystallization rate of Sb2Se3.

[0038] Fig.10 It is the relationship between the reflectivity of the sulfur-based phase-change FP resonant cavity at wavelengths of 1530nm, 1550nm and 1565nm and the crystallization rate of Sb2Se3.

[0039] Fig.11 is the minimum reflectivity and phase modulation amount of the chalcogenide phase change FP cavity at different wavelengths.

[0040] Figure numerals: 1. crystalline Si substrate; 2. Au reflective layer; 3. amorphous Si resonance wavelength adjustment layer; 4. Sb2Se3 chalcogenide phase change active layer; 5. Al2O3 layer; 6. amorphous Si layer. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The present invention is described in one of the embodiments in combination with the specific implementation methods. Among them, the drawings are only used for exemplary descriptions, and only schematic diagrams are shown, not physical drawings, and cannot be understood as limitations on the present invention; in order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0042] In the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only used for exemplary explanations and cannot be understood as limiting the present invention. For ordinary technicians in the field, the specific meanings of the above terms can be understood according to specific circumstances. In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or schemes that satisfy both A and B.

[0043] Embodiment 1:

[0044] The present embodiment provides a high-efficiency spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity, which includes, from bottom to top, a dielectric substrate, a reflective layer, a dielectric resonance wavelength adjustment layer, a chalcogenide phase change active layer, and a distributed Bragg reflector; the reflective layer provides a function of reflecting the spatial light field, the distributed Bragg reflector provides a semi-reflective and semi-transmissive function, and serves as a cavity medium of the FP resonant cavity; the chalcogenide phase change active layer serves as the cavity medium of the FP resonant cavity; wherein a portion of the chalcogenide phase change active layer is replaced by the dielectric resonance wavelength adjustment layer to compress the thickness of the chalcogenide phase change active layer.

[0045] According to the above technical means, when a spatial light field is incident, the metal reflective layer in the sulfur-based phase change FP resonant cavity provides the function of reflecting the spatial light field. The distributed Bragg reflector, on the one hand, provides a semi-reflective and semi-transmissive effect, and on the other hand, acts as the cavity medium of the FP resonant cavity. When the incident spatial light field meets the resonance condition of the FP cavity, resonance will be formed in the FP resonant cavity. The sulfur-based phase change active layer acts as the cavity medium of the FP cavity, and the resonance peak is displaced by virtue of the significant refractive index contrast brought about by the phase change process, thereby realizing the modulation of the phase of the reflected light field within the target band. Since the refractive index contrast of the sulfur-based phase change material during the phase change process is large, part of the sulfur-based phase change active layer can be replaced by a dielectric resonance wavelength adjustment layer, and the thickness of the sulfur-based phase change active layer as the active material can be compressed, thereby reducing the driving power consumption of the device and improving the modulation rate of the device.

[0046] The material of the dielectric substrate is a dielectric material with low absorption in the target band, including silicon oxide, silicon nitride, crystalline silicon or amorphous silicon. The thickness of the dielectric substrate is any choice much greater than the target wavelength, and is a flat plate structure. The material of the metal reflective layer is a metal material that can provide high reflection for the target band, including gold, aluminum, titanium or platinum. The thickness of the metal reflective layer is any choice that can provide high reflection for the target band, and is a thin film structure. The material of the dielectric resonance wavelength adjustment layer is a dielectric material with low absorption in the target band, including crystalline silicon, amorphous silicon, aluminum oxide, silicon oxide or gallium nitride. The thickness of the dielectric resonance wavelength adjustment layer is any choice less than the target wavelength, and is a thin film structure. The material of the sulfur-based phase change active layer is a sulfur-based phase change material, including Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3 or Sb2S3. The thickness of the sulfur-based phase change active layer is any choice less than the target wavelength, and is a thin film structure. The distributed Bragg reflector is composed of two films with different refractive indices that are stacked alternately and periodically; the materials of both films are dielectric materials with low absorption in the target band, including quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon, and the thickness of both films is designed based on the target wavelength and distributed Bragg reflection conditions.

[0047] When the target band is 1530nm~1565nm, the material of the dielectric substrate is a crystalline Si substrate with a thickness of 400μm~600μm; the material of the metal reflective layer is gold with a thickness of 90nm~110nm; the material of the dielectric resonance wavelength adjustment layer is amorphous Si with a thickness of 20nm~40nm; the material of the sulfide phase change active layer is Sb2Se3 with a thickness of 40nm~60nm; the distributed Bragg reflector is a single-period distributed Bragg reflector composed of an Al2O3 layer and an amorphous Si layer alternately and periodically stacked, and the thicknesses of the Al2O3 layer and the amorphous Si layer are 220nm~245nm and 115nm~135nm, respectively.

[0048] Example 2

[0049] like Figure 1 As shown, this embodiment provides a high-efficiency spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity, the target band is the C band (1530nm-1565nm), and the structure from bottom to top is: a crystalline Si substrate 1, an Au reflective layer 2, an amorphous Si resonance wavelength adjustment layer 3, a Sb2Se3 chalcogenide phase change active layer 4, an Al2O3 layer 5 and an amorphous Si layer 6, and the Al2O3 layer 5 and the amorphous Si layer 6 are alternately and periodically stacked to form a single-period distributed Bragg reflector.

[0050] The Au reflective layer 2 in the phase-change FP resonant cavity provides the function of reflecting the spatial light field. The single-period distributed Bragg reflector composed of the periodic stacking of the Al2O3 layer 5 and the amorphous Si layer 6 provides a semi-reflective and semi-transmissive function on the one hand, and acts as the cavity medium of the FP resonant cavity on the other hand. The thickness of the two layers follows the distributed Bragg reflection condition, that is:

[0051]

[0052] in, is the thickness of a layer of material in the distributed Bragg reflector, represents the target reflection wavelength, Represents the refractive index of a layer of material in the distributed Bragg reflector at the target reflection wavelength. In this design, The wavelength is selected as 1550nm. The refractive indices of Al2O3 and Si at 1550nm are approximately 1.6518 and 3.0547 respectively. According to calculation, the thickness of the Al2O3 layer and the amorphous Si layer are selected as 235nm and 125nm.

[0053] When the incident spatial light field meets the resonance conditions of the FP resonant cavity, resonance will be formed in the FP resonant cavity. The resonance conditions are as follows:

[0054]

[0055] In the formula, is the resonant wavelength, and Represent the effective medium refractive index and effective medium thickness of the FP cavity, is the incident angle of the spatial light field, and They represent the phase shift caused by the reflection of the spatial light field at the upper and lower interfaces respectively.

[0056] The Sb2Se3 sulfide phase change active layer 4 acts as the cavity medium of the FP resonant cavity, and the resonance peak moves due to the significant refractive index contrast brought by the phase change process, thereby realizing the modulation of the phase of the reflected light field. Since the refractive index contrast brought by the Sb2Se3 sulfide phase change active layer 4 during the phase change process is large, the amorphous Si resonance wavelength adjustment layer can be used to replace part of the Sb2Se3 sulfide phase change active layer 4, thereby compressing the thickness of the Sb2Se3 sulfide phase change active layer 4 as an active material.

[0057] The optical properties of the designed chalcogenide phase change FP resonant cavity were simulated by finite element method using the commercial software Lumerical FDTD. In the simulation model, the thickness of the Al2O3 layer 5 as the low refractive index layer of the distributed Bragg reflector and the amorphous Si layer 6 as the high refractive index layer of the distributed Bragg reflector are 235nm and 125nm respectively. The thickness of both layers follows the distributed Bragg reflection condition. The thickness of the Au reflection layer 2 is 100nm, the thickness of the amorphous Si resonance wavelength adjustment layer 3 and the Sb2Se3 chalcogenide phase change active layer 4 are 30nm and 50nm respectively, and the thickness of the crystalline Si substrate 1 is 500μm. The x and y directions of the phase change FP cavity are set as periodic boundary conditions to simulate the real metasurface periodic structure. The top and bottom of the chalcogenide phase change FP resonant cavity are set as perfect matching layers to simulate the real infinitely far isotropic medium environment.

[0058] In terms of the complex refractive index of materials, the complex refractive index of Au and crystalline Si is derived from the material database in the commercial software Lumerical FDTD, and the complex refractive index of Al2O3, amorphous Si and Sb2Se3 materials is derived from ellipsometer testing. Sb2Se3 materials are suitable chalcogenide phase change materials for pure phase regulation in the optical communication band. They have a large refractive index contrast and low optical loss. The extinction coefficient of any phase is close to zero, such as Figure 2 , Figure 3 and Figure 4 shown.

[0059] When the incident spatial light field meets the resonance condition of the FP resonant cavity, resonance will be formed in the FP resonant cavity, and high-efficiency phase modulation of the reflected light field close to 2π can be achieved during the phase change switching process of Sb2Se3. Figure 5 The reflection and transmission spectra of the sulfur-based phase-change FP cavity when the crystallization rate of Sb2Se3 is 59.5%, and it can be seen that there is a resonance peak at a wavelength of 1550nm. In order to characterize the excited resonance mode, the electric field absolute value distribution of the longitudinal section of the sulfur-based phase-change FP cavity at a wavelength of 1550nm when the crystallization rate of Sb2Se3 is 59.5% is simulated, as shown in Figure 1. Figure 6 As shown in FIG. 1 , it can be seen from the absolute value distribution of the electric field that there is a strong optical field localization in the amorphous Si resonance wavelength adjustment layer 3 and the Sb2Se3 chalcogenide phase change active layer 4 serving as the cavity medium of the FP resonant cavity.

[0060] In order to demonstrate the optical properties of the chalcogenide phase-change FP resonant cavity, the relationship between the phase and reflectivity of the chalcogenide phase-change FP resonant cavity and the crystallization rate of Sb2Se3 at different wavelengths was simulated, such as Figure 7 and Figure 8As shown in the figure, it is obvious that there is the resonance mode of the FP resonant cavity and the phase modulation of the reflected light field during the phase transition of Sb2Se3. Fig. 9 , 10 and 11 are the relationship between the phase modulation amount and reflectivity of the phase change FP resonant cavity and the crystallization rate of Sb2Se3 at wavelengths of 1530nm, 1550nm and 1565nm, as well as the minimum reflectivity and phase modulation amount of the sulfur-based phase change FP resonant cavity at different wavelengths. It can be seen that within the C-band (1530nm-1565nm), during the phase change process of Sb2Se3, the phase change FP resonant cavity always maintains a reflectivity greater than 60% and can achieve a phase modulation depth greater than 4π / 3.

[0061] Embodiment 3:

[0062] This embodiment provides a method for preparing a spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity, comprising the following steps:

[0063] S1. Vapor-depositing a metal film on a dielectric substrate as a metal reflective layer;

[0064] S2. depositing an amorphous Si film on the metal reflective layer as a dielectric resonance wavelength adjustment layer;

[0065] S3. growing a chalcogenide phase change film on the dielectric resonance wavelength adjustment layer as a chalcogenide phase change active layer; annealing the chalcogenide phase change film to fully crystallize it;

[0066] S4. Fabricating a distributed Bragg reflector on the chalcogenide phase change active layer;

[0067] The metal reflective layer provides the function of reflecting the spatial light field, the distributed Bragg reflector provides a semi-reflective and semi-transmissive effect, and at the same time serves as the cavity medium of the FP resonant cavity; the sulfide phase change active layer serves as the cavity medium of the FP resonant cavity; wherein, a part of the sulfide phase change active layer is replaced by a dielectric resonance wavelength adjustment layer to compress the thickness of the sulfide phase change active layer.

[0068] In step S1, a metal film is evaporated by electron beam evaporation; in step S2, an amorphous Si film is deposited on the metal film by an inductively coupled plasma enhanced chemical vapor deposition system; in step S3, a chalcogenide phase change film is grown on the amorphous Si film by a thermal evaporation system; in step S4, an Al2O3 film is sputtered on the chalcogenide phase change film by a magnetron sputtering method, and an amorphous Si film is deposited on the Al2O3 film by an inductively coupled plasma enhanced chemical vapor deposition system. The Al2O3 film and the amorphous Si film are periodically stacked alternately to form a single-period distributed Bragg reflector.

[0069] Among them, when the target band is 1530nm~1565nm, the dielectric substrate is a crystalline Si substrate with a thickness of 400μm~600μm; the reflective layer is a gold reflective layer with a thickness of 90 nm~110nm; the material of the dielectric resonance wavelength adjustment layer is amorphous Si with a thickness of 20nm~40nm; the material of the sulfur-based phase change active layer is Sb2Se3 with a thickness of 40nm~60nm; the thickness of the Al2O3 film is 220nm~245nm; the thickness of the amorphous Si film is 115nm~135nm.

[0070] The present embodiment provides a method for preparing a spatial light field phase modulation device based on a sulfur-based phase change FP resonant cavity. Compared with the spatial light field phase modulation device based on an active metasurface, the process flow for preparing the proposed high-efficiency spatial light field phase modulation device based on a sulfur-based phase change FP resonant cavity only involves thin film growth and does not involve the processing technology of micro-nano structures. The preparation process is relatively simple, the cost is low, and the difficulty is relatively low.

[0071] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0072] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity, characterized in that: The invention comprises, from bottom to top, a dielectric substrate, a reflection layer, a dielectric resonance wavelength adjustment layer, a chalcogenide phase change active layer, and a distributed Bragg reflector; the reflection layer provides a function of reflecting a spatial light field, the distributed Bragg reflector provides a semi-reflective and semi-transmissive function, and serves as a cavity medium of the FP resonant cavity; the chalcogenide phase change active layer serves as a cavity medium of the FP resonant cavity; wherein the dielectric resonance wavelength adjustment layer is used to replace part of the chalcogenide phase change active layer to compress the thickness of the chalcogenide phase change active layer.

2. The spatial light field phase modulation device based on the chalcogenide phase change FP resonant cavity according to claim 1 is characterized in that: The material of the dielectric substrate is a dielectric material with low absorption in the target wavelength band, including silicon oxide, silicon nitride, crystalline silicon or amorphous silicon, and the thickness is any one selected to be greater than the target wavelength.

3. The spatial light field phase modulation device based on the chalcogenide phase change FP resonant cavity according to claim 1 is characterized in that: The material of the reflective layer is a metal material that can provide high reflection for the target band, including gold, aluminum, titanium or platinum; the thickness is any option that can provide high reflection for the target band, wherein high reflection means a reflectivity greater than 90%.

4. The spatial light field phase modulation device based on the chalcogenide phase change FP resonant cavity according to claim 1 is characterized in that: The material of the dielectric resonance wavelength adjustment layer is a dielectric material with low absorption in the target wavelength band, including crystalline silicon, amorphous silicon, aluminum oxide, silicon oxide or gallium nitride; the thickness is any one of the options less than the target wavelength.

5. The spatial light field phase modulation device based on the chalcogenide phase change FP resonant cavity according to claim 1, characterized in that: The material of the chalcogenide phase change active layer is a chalcogenide phase change material, including Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3 or Sb2S3; the thickness is any one of the options smaller than the target wavelength.

6. The spatial light field phase modulation device based on the chalcogenide phase change FP resonant cavity according to claim 1, characterized in that: The distributed Bragg reflector is composed of two films with different refractive indices that are periodically stacked alternately; wherein the material of the high refractive index film includes chalcogenide phase change material, quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon, and the material of the low refractive index film includes quartz glass, aluminum oxide, silicon nitride, crystalline or amorphous silicon; the thickness of the two films are set based on the target wavelength and the distributed Bragg reflection conditions.

7. The spatial light field phase modulation device based on the chalcogenide phase change FP resonant cavity according to claim 6, characterized in that: When the target band is 1530nm~1565nm, the material of the dielectric substrate is a crystalline Si substrate with a thickness of 400μm~600μm; the material of the reflective layer is gold with a thickness of 90nm~110nm; the material of the dielectric resonance wavelength adjustment layer is amorphous Si with a thickness of 20nm~40nm; the material of the sulfide phase change active layer is Sb2Se3 with a thickness of 40nm~60nm; the distributed Bragg reflector is a single-period distributed Bragg reflector composed of an Al2O3 layer and an amorphous Si layer alternately and periodically stacked, and the thicknesses of the Al2O3 layer and the amorphous Si layer are 220nm~245nm and 115nm~135nm, respectively.

8. A method for preparing a spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity, characterized in that: The following steps are involved: S1. Vapor-depositing a metal film on a dielectric substrate as a metal reflective layer; S2. depositing an amorphous Si film on the metal reflective layer as a dielectric resonance wavelength adjustment layer; S3. growing a chalcogenide phase change film on the dielectric resonance wavelength adjustment layer as a chalcogenide phase change active layer; annealing the chalcogenide phase change film to fully crystallize it; S4. Fabricating a distributed Bragg reflector on the chalcogenide phase change active layer; The metal reflective layer provides a function of reflecting the spatial light field, the distributed Bragg reflector provides a semi-reflective and semi-transmissive effect, and at the same time serves as a cavity medium of the FP resonant cavity; the sulfide phase change active layer serves as the cavity medium of the FP resonant cavity; wherein, the medium resonance wavelength adjustment layer is used to replace part of the sulfide phase change active layer to compress the thickness of the sulfide phase change active layer.

9. The method for preparing a spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity according to claim 8, characterized in that: In step S1, a metal film is evaporated by electron beam evaporation; in step S2, an amorphous Si film is deposited on the metal film by an inductively coupled plasma enhanced chemical vapor deposition system; in step S3, a chalcogenide phase change film is grown on the amorphous Si film by a thermal evaporation system; in step S4, an Al2O3 film is sputtered on the chalcogenide phase change film by a magnetron sputtering method, and an amorphous Si film is deposited on the Al2O3 film by an inductively coupled plasma enhanced chemical vapor deposition system. The Al2O3 film and the amorphous Si film are periodically stacked alternately to form a single-period distributed Bragg reflector.

10. The method for preparing a spatial light field phase modulation device based on a chalcogenide phase change FP resonant cavity according to claim 9, characterized in that: When the target band is 1530nm~1565nm, the dielectric substrate is a crystalline Si substrate with a thickness of 400μm~600μm; the metal reflective layer is a gold reflective layer with a thickness of 90nm~110nm; the material of the dielectric resonance wavelength adjustment layer is amorphous Si with a thickness of 20nm~40nm; the material of the sulfur-based phase change active layer is Sb2Se3 with a thickness of 40nm~60nm; the thickness of the Al2O3 film is 220nm~245nm; the thickness of the amorphous Si film is 115nm~135nm.

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