Chalcogenide phase change metamaterial surface spatial light multi-order regulation and control device and method based on phase change-thermo-optical synergistic effect

Abstract

The invention relates to the technical field of light field regulation and control, in particular to a chalcogenide phase change metasurface spatial light multi-order regulation and control device and method based on a phase change-thermo-optical synergistic effect. And the temperature of the phase-change material in the metasurface is accurately controlled by using the micro-thermode module. Non-volatile coarse tuning of phase change is carried out on the phase change material through high-voltage electric pulses, volatile fine tuning is carried out on the phase change material by heating the phase change material through low-voltage pulses which do not trigger phase change, and multi-order spatial light regulation and control based on cooperation of phase change coarse tuning and thermo-optic fine tuning is achieved. Therefore, the device can have a large-range working point setting capability and a high-precision dynamic fine tuning capability at the same time, and wide-range and high-precision integrated control is realized.

Description

Technical Field

[0001] This application relates to the field of light field modulation technology, and more specifically, to a device and method for multi-level spatial light modulation of chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect. Background Technology

[0002] Metasurfaces are ultrathin two-dimensional arrays of subwavelength-scale artificial scattering structures arranged at subwavelength intervals on a substrate. By designing the geometric parameters and refractive index of the subwavelength-scale scattering units, parameters such as phase, intensity, and polarization of the incident light field can be modulated. Due to their fixed device structure, the functional characteristics of metasurfaces cannot be changed once they are designed and fabricated, limiting their application to static modulation scenarios. To overcome the limitations of static metasurfaces, researchers combine different active materials with metasurfaces to construct dynamically modulated metasurfaces. Currently, the main active materials include semiconductors, liquid crystals, microelectromechanical systems (MEMS) materials, and phase change materials (PCMs). Semiconductors, liquid crystals, and MEMS materials face numerous bottlenecks and trade-offs in terms of modulation range, power consumption, and speed. Phase change materials (PCMs) based on chalcogenides offer a novel, non-volatile modulation method for spatial light modulation devices. PCMs possess two stable and reversibly convertible microstructural phases (crystalline and amorphous). These two phases exhibit significant differences in electrical and optical properties, especially in the visible to infrared bands, where the refractive index can be tuned on the order of Δn~1. Unlike traditional active materials, phase change materials do not require a continuous external energy supply to maintain their phase state after switching. Furthermore, phase change materials possess rapid (ns-level) reconfigurable switching, multiple cycles, and stability (>10). 9 (secondary) and the potential to achieve multiple levels.

[0003] The extinction coefficient of amorphous chalcogenide phase change materials is generally small, but the extinction coefficient of crystalline chalcogenide materials is not negligible. The extinction coefficient gradually increases with increasing crystallinity, reaching its maximum in the fully crystalline state. Currently, the widely studied Ge-Sb-Te materials still exhibit non-zero absorption even in their low-loss amorphous state (extinction coefficient k≈0.02), and the coupling between loss and phase modulation results in low efficiency for spatial optical field phase modulation, limiting their application scenarios. Furthermore, achieving precise and controllable multi-level modulation by controlling the degree of phase transition remains challenging. The slightly different amorphous states caused by the random melting-quenching process during phase transition further lead to significantly different and random crystalline states during subsequent long-range nucleation-growth, limiting the reliability and consistency of multi-level modulation and making it difficult to achieve high multi-level modulation accuracy and order, thus limiting device usability. For metasurface spatial light modulation devices, the device units are larger than integrated optical devices (on the order of tens of micrometers), and the larger phase change material volume further exacerbates the inconsistency of multi-level modulation. Furthermore, phase transitions in large-area phase transition materials require a longer lattice nucleation and growth process, which limits the control of rapid phase transitions. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies in phase change materials, which are difficult to achieve high multi-level control accuracy and order when performing phase change control. It provides a spatial light multi-level control device and method for sulfide phase change metasurfaces based on the synergistic effect of phase change-thermo-optic, which significantly improves the multi-level control accuracy and control range of phase change metasurfaces.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A multi-stage spatial light control device based on phase change-thermo-optic synergy is provided, which includes a microthermal electrode module and a metasurface module from bottom to top. The microthermal electrode module can generate heat through the resistive heating effect and transfer the heat to the phase change material functional layer. The metasurface module includes a modulation functional layer and a metasurface structure. It uses a chalcogenide phase change material to achieve modulation function and can realize the refractive index change and optical field modulation of the phase change material through phase change and / or thermo-optic effect. The micro-thermal electrode module can use high-voltage electrical pulses to heat and regulate the functional layer to trigger phase change materials to achieve phase changes of different degrees, thereby achieving non-volatile coarse adjustment; the micro-thermal electrode module can use low-voltage pulses to heat and regulate the functional layer, and use the thermo-optic effect of the phase change material to achieve volatile fine adjustment. The low-voltage pulses do not trigger phase changes in the phase change material, and the temperature is lower than the crystallization temperature of the phase change material.

[0006] This invention discloses a multi-stage spatial light modulation device for chalcogenide phase change metasurfaces based on the synergistic effect of phase change and thermo-optical interaction. It utilizes a micro-thermal electrode module to accurately control the temperature of the phase change material in the metasurface. Non-volatile coarse adjustment of the phase change material is achieved through high-voltage electrical pulses, while volatile fine adjustment is performed by heating the phase change material with low-voltage pulses that do not trigger the phase change. This achieves multi-stage spatial light modulation through the synergistic effect of "phase change coarse adjustment and thermo-optical fine adjustment." The device simultaneously possesses the ability to set a wide operating point and high-precision dynamic fine-tuning capabilities, realizing integrated control with a wide range and high precision.

[0007] Furthermore, the microthermal electrode module comprises, from bottom to top: Substrate; Heating electrodes are used to generate heat through the resistive heating effect and transfer the heat to the functional layer of the phase change material. The electrode lead layer is used to make two contacts with the heating electrode and extend outward to connect with the external control current. An insulating layer is used to isolate the heating electrode from the air and the metasurface.

[0008] Furthermore, the heating electrode is made of metallic materials such as silver, tungsten, titanium, or platinum, as well as transparent conductive oxides or other novel transparent electrodes, and the size of the heating electrode is larger than that of the phase change material layer; the electrode lead layer is made of metallic materials such as gold, silver, tungsten, titanium, or platinum; and the insulating layer is made of aluminum oxide or silicon oxide.

[0009] Furthermore, the metasurface module is not limited to a specific hierarchical structure, and consists of a core control functional layer made of phase change material, as well as other necessary auxiliary structural materials as a reflective layer, a transmissive layer, an isolation layer, a protective layer, or other functional layers.

[0010] Furthermore, the metasurface module comprises, from bottom to top: Metal reflective layer; A dielectric isolation layer is used to isolate the metasurface resonant mode field from the metal reflective layer; Regulation and control functional layer; The dielectric protective layer is used to isolate air and regulate the functional layers.

[0011] Furthermore, the metasurface module's control function and the control function material rely solely on the phase change material, and the phase change and / or thermo-optic effect are generated solely by the phase change material.

[0012] Furthermore, the metasurface includes an array of micro- and nanostructures, which include cylindrical structures, square pillar structures, negative cylindrical structures, negative square pillar structures, or topological pillar structures. The longitudinal thickness of the micro- and nanostructures is any choice less than the target wavelength, and the lateral dimension is any choice less than the metasurface period.

[0013] Furthermore, the phase change material includes Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, or Sb2S3.

[0014] Furthermore, the material of the metal reflective layer is a metal material capable of providing high reflectivity to the target wavelength; the thickness of the metal reflective layer is any choice capable of providing high reflectivity to the target wavelength; and high reflectivity means a reflectivity greater than 90%.

[0015] Furthermore, the material of the metal reflective layer includes gold, aluminum, titanium, or platinum; the material of the dielectric isolation layer includes aluminum oxide or silicon oxide, and the thickness of the dielectric isolation layer is any choice less than the target wavelength; the material of the dielectric protective layer includes aluminum oxide or silicon oxide, and the thickness of the dielectric protective layer is any choice less than the target wavelength.

[0016] This invention also provides a method for multi-level spatial light modulation of chalcogenide phase change metasurfaces based on the synergistic effect of phase change and thermo-optics, using the aforementioned apparatus and comprising the following steps: Non-volatile coarse adjustment: Applying a high-voltage electrical pulse to the micro-thermal electrode module heats and modulates the functional layer, triggering the phase change material to achieve phase changes of different degrees, thereby achieving non-volatile coarse adjustment; Volatility fine-tuning: Low-voltage pulse heating is applied to the micro-thermal electrode module to regulate the functional layer. Volatility fine-tuning is achieved by utilizing the thermo-optical effect of the phase change material. The low-voltage pulse does not trigger the phase change of the phase change material, and the temperature is lower than the crystallization temperature of the phase change material.

[0017] Furthermore, during non-volatile coarse tuning, a high-voltage electrical pulse is applied to heat the phase change material to its crystallization temperature to induce crystallization, or to its melting temperature to induce decrystallization. Different degrees of crystallization are achieved by controlling the voltage magnitude, roughly locating the target modulation state. During volatile fine tuning, the non-volatility of the phase change material is considered to set an initial static operating point for the device. Then, a low-voltage pulse is applied to heat the phase change material, increasing its temperature without changing the static operating point. The thermo-optic effect of the phase change material is used for small-range, continuous, and dynamic fine tuning to accurately compensate for deviations and bring the device to the target modulation state. During volatile fine tuning, the low-voltage pulse can be maintained or terminated as needed.

[0018] Furthermore, it also includes controlling the optical parameters of incident spatial light by changing the hierarchy of the metasurface structure or the size or shape of the micro / nano structure array, wherein the optical parameters include amplitude, phase, and polarization.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention discloses a multi-stage spatial light modulation device and method based on the synergistic effect of phase change and thermo-optical interaction on a chalcogenide phase change metasurface. By utilizing the large refractive index change, non-volatile properties, and continuously tunable thermo-optical effects of phase change materials, a novel control paradigm combining non-volatile coarse tuning and volatile fine tuning is constructed. This invention successfully solves the technical contradictions of existing single modulation techniques in achieving a wide range, high precision, repeatability, and low power consumption, realizing a compact, highly capable, and stable spatial light modulation device.

[0020] 2. This invention possesses excellent multi-level control capabilities: the synergistic combination of "non-volatile coarse tuning + volatile fine tuning" creatively integrates the non-volatile "coarse tuning" of phase change materials with the continuous "fine tuning" of thermo-optic effects; high-voltage pulses (triggering phase transitions) achieve non-volatile coarse tuning, while low-voltage pulses (not triggering phase transitions, temperature < crystallization temperature) utilize thermo-optic effects to achieve volatile fine tuning. By combining the non-volatile wide-range modulation of phase transitions with the stable continuous modulation characteristics of thermo-optics, the randomness and limited durability of phase change materials are avoided, achieving wide-range, precise, and consistent multi-level spatial light control.

[0021] 3. This invention balances non-volatility and dynamic adjustability, with a flexible and efficient control mechanism: This invention combines "phase-change non-volatile coarse adjustment + thermo-optical volatile fine adjustment," which retains the non-volatility of phase change (the coarse adjustment state is not lost after power failure) and achieves dynamic fine adjustment through thermo-optical effects (adapting to environmental changes or real-time signal adjustments). This enables the device to simultaneously possess the ability to set a wide range of operating points and high-precision dynamic fine adjustment capabilities, achieving integrated control with a wide range and high precision.

[0022] 4. This invention features lower power consumption: Thanks to the non-volatility of the phase change material, after coarse adjustment, the device does not require continuous power to maintain its operating state. When dynamic fine adjustment is needed, the heating electrode unit only requires lower power for fine-tuning. Therefore, the overall average power consumption is lower, depending on the achievable multi-level PCM and the time the system needs to maintain the thermo-optical state.

[0023] 6. This invention offers higher control efficiency: This invention utilizes a phase change material with a large refractive index change. The refractive index change between the crystalline and amorphous states of this type of material can reach the order of Δn~1, allowing for the same control range to be achieved with a smaller device size. This increases the thickness of the metasurface integration and helps reduce material loss and improve response speed.

[0024] 7. This invention does not require the introduction of modulation mechanisms of other materials (such as doped silicon, lithium niobate, etc.). This invention only relies on phase change materials to achieve "phase change coarse tuning + thermo-optical fine tuning", avoiding the device processing difficulty (such as differences in deposition temperature and etching rate of different materials) and material system complexity (such as lattice matching) that may be caused by the superposition of multiple modulation mechanisms. At the same time, it reduces the additional optical loss caused by mode coupling or interface effects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the first-view structure of a phase-change metasurface spatial light multi-level modulation device in one embodiment. Figure 2 This is a schematic diagram of the second-view structure of a phase-change metasurface spatial light multi-level modulation device in one embodiment. Figure 3 This is a flowchart illustrating a method for multi-level spatial light modulation of phase-change metasurfaces in one embodiment. Figure 4 The refractive index spectrum of Sb₂Se₃ in another embodiment; Figure 5 The metasurface reflection spectrum is obtained by applying different voltages in one embodiment. Figure 6 This is a curve showing the change of the resonance peak wavelength with the electrical pulse voltage in one embodiment; Figure 7 Thermo-optical reflectance spectra of amorphous metasurface devices at different voltages (0-3V) in one embodiment; Figure 8 The wavelength variation of the resonance peak of the reflection spectrum of a crystalline metasurface device under different voltages (0-3V) in one embodiment is shown. Figure 9 The wavelength variation of the resonance peak of the reflection spectrum of an amorphous metasurface device under different voltages (0-3V) in one embodiment is shown.

[0026] In the attached diagram: 1. Microthermal electrode module; 11. Substrate; 12. Heating electrode; 13. Electrode lead layer; 14. Insulating isolation layer; 2. Metasurface module; 21. Metal reflective layer; 22. Dielectric isolation layer; 23. Control function layer; 24. Dielectric protection layer. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0028] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0029] Example 1 This embodiment is an example of a multi-level spatial light modulation device for a chalcogenide phase change metasurface based on the synergistic effect of phase change and thermo-optics. Figure 1 and Figure 2 As shown, from bottom to top, it includes a microthermal electrode module 1 and a metasurface module 2; The microthermal electrode module 1 includes, from bottom to top: Substrate 11: A flat, insulating substrate 11 provides mechanical support for the device while preventing electromagnetic interference from electrode currents. The material can be quartz glass, with a thickness of any choice that is much greater than the target wavelength, ensuring stable support. Heating electrode 12: The metal electrode generates heat through resistive heating and transfers the heat to the control functional layer 23. The metal electrode materials include, but are not limited to, silver, tungsten, titanium and platinum. A typical structure is a titanium electrode with a thickness of 75 nm, and its size and area are larger than the subsequent metasurface structure to ensure uniform heating of the device. Electrode lead layer 13: A metal lead made of high-conductivity material, contacting both sides of the heating electrode 12 and extending outwards to connect to an external control circuit. It is used to transmit electrical signals from the external control circuit, precisely delivering current to the heating electrode 12. The metal lead material includes, but is not limited to, highly conductive materials such as gold, silver, tungsten, titanium, and platinum; a typical structure is gold (Au) with a thickness of 900 nm. This thickness is to improve the success rate of subsequent gold wire bonding. Insulating layer 14: The dielectric material isolates the heating electrode 12 from the air and the metasurface, preventing Ti from deteriorating at high temperatures and ensuring device performance and cycle life. The dielectric material includes, but is not limited to, alumina and silicon oxide, with a typical structure being Al2O3 with a thickness of 30 nm.

[0030] Metasurface module 2, from bottom to top, includes: Metal reflective layer 21: The material is a metal material that can provide high reflectivity to the target wavelength, including but not limited to gold, aluminum, titanium and platinum, and the thickness is any choice that can provide high reflectivity to the target wavelength, with a typical thickness of 100 nm. The dielectric isolation layer 22, made of a dielectric material with low absorption in the target wavelength band, is used to isolate the metasurface resonant mode field from the metal reflective layer 21, avoiding strong absorption by the metal layer. The dielectric material includes, but is not limited to, alumina and silicon oxide, and its thickness is any choice less than the target wavelength. A typical structure is Al2O3 with a thickness of 100 nm. The aforementioned low absorption requirement means that the loss introduced by this material accounts for a small proportion of the total metasurface loss, less than 10%. The modulation functional layer 23 is a metasurface structure that uses phase change materials to achieve modulation functionality. It can achieve refractive index changes and optical field modulation through phase change and / or thermo-optic effects. Alternatively, it can use chalcogenide phase change materials to achieve modulation functionality, achieving refractive index changes and optical field modulation through phase change or thermo-optic effects. These materials include, but are not limited to, Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, or Sb2S3, with longitudinal thickness of any choice less than the target wavelength and lateral dimensions of any choice less than the metasurface period. The structure is columnar, including but not limited to cylindrical, square, negative cylindrical, negative square, and topological columnar structures. A typical structure is a 200 nm Sb2Se3 structure with a circular aperture array. The dielectric protective layer 24, made of a dielectric material with low absorption in the target wavelength band, isolates the device from the air and the modulation functional layer 23, preventing oxidation during the high-temperature phase transition process and ensuring device performance and cycle life. Furthermore, due to the melting process during the die-off process, it also plays a role in maintaining the device's shape. The dielectric material includes, but is not limited to, alumina and silicon oxide, with a thickness of any choice less than the target wavelength; a typical structure is 30 nm thick Al₂O₃.

[0031] The above metasurface structure is only an example of a reflective metasurface. In this invention, there are no special restrictions on the specific structure of the metasurface, as long as it is a dynamically controllable metasurface achieved by using phase change materials.

[0032] In this embodiment, the micro-thermal electrode module 1 can use high-voltage electrical pulses to heat and regulate the functional layer 23 to trigger phase change materials to achieve phase changes of different degrees, thereby achieving non-volatile coarse adjustment; the micro-thermal electrode module 1 can use low-voltage pulses to heat and regulate the functional layer 23, and use the thermo-optic effect of the phase change material to achieve volatile fine adjustment. The low-voltage pulses do not trigger phase changes in the phase change material, and the temperature is lower than the crystallization temperature of the phase change material.

[0033] Working principle: When a spatial light field is incident, special resonance modes can be excited in the micro- and nano-structures of the metasurface. By rationally designing the various geometric parameters of the metasurface unit structure, including the period, the longitudinal thickness of each layer, and the lateral dimensions of the chalcogenide phase transition microstructure, the light field can be controlled in multiple parameters, such as amplitude, phase, and polarization.

[0034] In this embodiment, the reflective phase modulation metasurface allows the resonant mode to couple with its mirror resonant mode due to the presence of the metal reflective layer 21. By adjusting the circular aperture array, the resonant mode can be kept in an overcoupled state throughout the phase transition process of the chalcogenide phase change material. Near the resonant wavelength of the mode, the reflected light field undergoes a 2π phase change. Using the phase change material as the modulation medium, its refractive index change causes a shift in the mode's resonant wavelength. For a fixed wavelength, the reflected light field can achieve a phase change. When the resonant mode completely deviates from its original wavelength, a full 2π phase depth can be achieved. The range covered by the resonant wavelength shift corresponds to the working spectral band that can achieve a 2π phase.

[0035] The device provided in this embodiment utilizes microthermal electrodes to accurately control the temperature of phase change materials in a metasurface. High-voltage electrical pulses are used for non-volatile coarse adjustment of the phase change material's phase transition, while low-voltage pulses that do not trigger a phase transition are used to heat the material for volatile fine adjustment, achieving multi-level spatial optical modulation through a synergistic "phase change coarse adjustment - thermo-optical fine adjustment." During modulation, the significant refractive index change generated by the phase change of the material provides a large modulation range for the device. By applying high-voltage electrical pulses, the material is heated to its crystallization temperature (causing crystallization) or to its melting temperature (higher than the crystallization temperature) (causing decrystallization). Controlling the voltage magnitude achieves different degrees of crystallization, roughly locating the target modulation state. Combining the non-volatility of the phase transition, an initial static operating point is set for the device. Then, relatively low-voltage electrical pulses are applied to raise the temperature of the phase change material to below the crystallization temperature, i.e., without changing the static operating point. The thermo-optical effect of the phase change material is used for small-range, continuous, and dynamic fine adjustment to accurately compensate for deviations. Because the modulation achieved by the thermo-optic effect is volatile, the modulation state recovers after the voltage ends, and the fine-tuning state of the thermo-optic effect can be maintained or terminated as needed.

[0036] It is worth noting that the specific required phase transition voltage and thermo-optic voltage range are related to the sample structure. In order not to trigger the crystallization phase transition, the thermo-optic voltage range is usually smaller than the crystallization voltage. The electric pulse voltage that can reach the crystallization temperature varies depending on the heating electrode and metasurface size, and needs to be determined based on simulation and previous experiments.

[0037] This embodiment presents a multi-stage spatial light control device for a chalcogenide phase change metasurface based on the synergistic effect of phase change and thermo-optical interaction. It utilizes a micro-thermal electrode module 1 to accurately control the temperature of the phase change material in the metasurface. High-voltage electrical pulses are used to perform non-volatile coarse adjustment of the phase change material, while low-voltage pulses that do not trigger the phase change are used to heat the material for volatile fine adjustment. This achieves multi-stage spatial light control through the synergistic effect of "phase change coarse adjustment - thermo-optical fine adjustment." The device simultaneously possesses the ability to set a wide operating point and high-precision dynamic fine-tuning capabilities, realizing integrated control with a wide range and high precision.

[0038] Example 2 This embodiment is an example of a spatial light multi-level modulation method for chalcogenide phase change metasurfaces based on the synergistic effect of phase change and thermo-optics. This embodiment uses a device similar to that in Embodiment 1 and specifically includes the following steps: Non-volatile coarse adjustment: Applying a high-voltage electrical pulse to the microthermal electrode module 1 heats the control functional layer 23, triggering the phase change material to achieve phase changes of different degrees, thereby achieving non-volatile coarse adjustment; Volatility fine-tuning: Apply low-voltage pulse heating control layer 23 to micro-thermal electrode module 1 to achieve volatility fine-tuning by utilizing the thermo-optic effect of phase change material. The low-voltage pulse does not trigger phase change of phase change material and the temperature is lower than the crystallization temperature of phase change material.

[0039] In the non-volatile coarse tuning process, a high-voltage electrical pulse is applied to heat the phase change material to its crystallization temperature, causing crystallization, or to its melting temperature, causing decrystallization. Different degrees of crystallization are achieved by controlling the voltage, roughly locating the target modulation state. In the volatile fine tuning process, the non-volatility of the phase change material is considered to set an initial static operating point for the device. Then, a low-voltage pulse is applied to heat the phase change material, increasing its temperature without changing the static operating point. The thermo-optic effect of the phase change material is used for small-range, continuous, and dynamic fine tuning to accurately compensate for deviations and bring the device to the target modulation state. During the volatile fine tuning process, the low-voltage pulse can be maintained or terminated as needed.

[0040] In this embodiment, the optical parameters of incident spatial light are controlled by changing the hierarchy of the metasurface structure or the size or shape of the micro / nano structure array. The optical parameters include amplitude, phase, and polarization.

[0041] In this embodiment, the non-volatility of the phase change material is utilized, so no continuous power supply is required after coarse adjustment; only low-power heating is needed during fine adjustment, which effectively reduces the overall average power. In this embodiment, the large refractive index of the phase change material is used to reduce the size of the device, increase the thickness of the metasurface integration, effectively improve the response speed and reduce material loss.

[0042] like Figure 3 As shown, the specific steps involved in regulation are as follows: Step 1: Initial state determination and target setting: Measure the current light field modulation state of the metasurface to determine whether the target effect exceeds the range that the thermo-optic effect can adjust; Step 2: Perform non-volatile coarse adjustment: By applying a specific voltage pulse to the phase change metasurface to control its crystallization degree, a wide range of non-volatile coarse adjustment is achieved, setting the metasurface to near the target modulation state; Step 3: Verify the current modulation state: Measure the current light field modulation state of the metasurface again to determine if the target effect has been achieved; if not, determine whether the target effect under the current modulation state still exceeds the range that the thermo-optic effect can adjust; if it does, continue to step 2; if it does not, proceed to step 4; if so, proceed to step 5. Step 4: Perform volatile fine-tuning: Based on the measurement results of Step 3, perform precise fine-tuning compensation on the metasurface through low-voltage thermo-optical effect; Step 5: Reach the target state: Continuously supply power to maintain the effect of thermo-optical fine-tuning according to the required state holding time, until the current modulation state is no longer needed or the next modulation command is received.

[0043] The multi-level spatial light modulation method for electrically controlled phase-change metasurfaces provided in this embodiment starts by receiving a switching command. It accurately measures the current light field modulation state (e.g., by measuring the reflection spectrum) and determines the required adjustment strategy based on the desired modulation state. If the modulation exceeds the range adjustable by the thermo-optical effect, coarse adjustment is first performed using the non-volatile properties of the phase-change material. A specific voltage pulse is applied to control its crystallization degree, quickly establishing a basic operating point. Subsequently, the modulation state of the metasurface is verified again to determine the required adjustment strategy, and a low-voltage thermo-optical effect is used for precise fine-tuning compensation. This hierarchical modulation mechanism ensures both a wide range of setting capabilities and high-precision stable control, achieving synergistic multi-level light field modulation of "wide-range non-volatile coarse adjustment + high-precision volatile fine adjustment." It balances the modulation range and accuracy, solving the problem of high randomness in traditional phase-change metasurface modulation.

[0044] Example 3 This embodiment verifies the solution provided in Embodiment 1 or Embodiment 2 by designing a specific device structure.

[0045] In this embodiment, an Sb₂Se₃ electrically controlled metasurface device was designed, such as... Figure 1 and Figure 2 As shown, the structure from bottom to top is as follows: Substrate 11 is made of Si substrate and SiO2 substrate; heating electrode 12 is made of Ti heating electrode; electrode lead layer 13 is made of Au electrode lead; insulating isolation layer 14 is made of Al2O3 isolation layer; metal reflective layer 21 is made of Au reflective layer; dielectric isolation layer 22 is made of Al2O3 dielectric layer; control function layer 23 is made of Sb2Se3 with a circular hole array metasurface structure; dielectric protection layer 24 is made of Al2O3 protective layer.

[0046] In this embodiment, SbSe is selected as the core phase change material, and its refractive index characteristic curve in the 250-1850nm wavelength range is shown below. Figure 4 As shown. By Figure 4It is known that this material exhibits high refractive index characteristics in both its crystalline (cSbSe) and amorphous (aSbSe) states in the near-infrared band, and the refractive index change between the crystalline and amorphous states is on the order of Δn ≈ 1, providing ample modulation space for coarse tuning over a wide range. More importantly, its amorphous state has an absorption coefficient k ≈ 10 in the optical communication window (around 1550 nm). -5 With an absorption rate close to zero, it can significantly reduce energy loss when the light field interacts with the material, ensuring high efficiency in light modulation.

[0047] In this embodiment, a device fabrication method is provided, comprising: firstly, depositing a 75 nm thick Ti heating electrode layer on a SiO2 substrate using electron beam evaporation, and then fabricating a rectangular pattern using a lift-off method. Next, Au electrode leads are fabricated using the same process and placed across the two ends of the Ti heating electrode. To isolate the electrode from the upper metasurface structure, a 30 nm thick Al2O3 isolation layer is grown using atomic layer deposition (ALD). Then, the metasurface is fabricated using a lift-off method, successively depositing a 100 nm thick Au reflective layer using electron beam evaporation, growing a 30 nm thick Al2O3 dielectric layer using ALD, and thermally evaporating a 200 nm thick Sb2Se3 layer, followed by a lift-off process to form the metasurface region. A circular via array is etched on the SbSe layer using inductively coupled plasma reactive ion etching (ICP-RIE) with a period of 800 nm and a radius of 250 nm. Finally, a 30 nm thick Al2O3 protective layer is grown on the surface of the Sb2Se3 layer using ALD. The core advantage of the fabrication process in this embodiment is that it achieves synergistic control of phase transition and thermo-optics using only a Ti heating electrode as the control structure, without introducing other auxiliary modulation materials such as doped silicon or lithium niobate. This effectively avoids the processing difficulties caused by differences in deposition temperature and etching rate mismatch between different materials, while reducing problems such as lattice mismatch and additional loss of mode coupling caused by multi-material systems, simplifying the process and ensuring the consistency of device performance.

[0048] To determine the critical voltage for the crystallization phase transition of Sb₂Se₃, an electrical pulse with a pulse width of 1 s and a gradually increasing voltage was applied to the device, and the change in the reflection spectrum was measured. The results are as follows: Figure 5 As shown, when a voltage of 0V is applied (the device is initially in an amorphous state), the resonance peak of the reflection spectrum is located at 1490 nm. After applying a 3.6V electrical pulse, the resonance peak exhibits a significant redshift. After applying a 4.2V electrical pulse, the redshift of the resonance peak further increases, and the spectral state remains stable after the electrical pulse ends, verifying the non-volatility of the phase transition. Thanks to the large refractive index difference between the Sb₂Se₃ crystalline and amorphous states, the maximum spectral redshift can reach 100 nm, achieving a wide range of coarse tuning.

[0049] Figure 6The curve shows the change in resonance peak wavelength with electrical pulse voltage: when the voltage reaches 3.2V, the resonance peak begins to shift (phase transition is initiated); when the voltage rises to 4V and above, the resonance peak shift becomes gradual, indicating that the device has reached its maximum crystallinity. Based on this test result, to ensure that subsequent thermo-optical modulation does not trigger a phase transition, the thermo-optical modulation voltage range is set to 0-3V (within this voltage range, the device temperature is below the Sb2Se3 crystallinity temperature).

[0050] Thermo-optic modulation tests were performed on the amorphous device within the voltage range of 0-3V, with a voltage scan step of 0.1V. The results are shown in Figure 7. Figure 7 The spectral thermogram in (a) clearly shows that the resonance peaks shift continuously and regularly as the voltage increases; Figure 7 (b) shows the reflection spectrum at 0V (no power) and 3V. It can be seen that the resonance peak shift caused by thermo-optic modulation is about 12nm. After the 3V voltage is removed, the spectrum is completely restored to the state at 0V, which fully verifies the volatility of thermo-optic modulation.

[0051] For the crystallized device, repeated thermo-optic modulation tests were performed within a voltage range of 0-3V, and the results are as follows: Figure 8 As shown: Figure 8 The spectral thermogram in (a) shows that the device still has stable thermo-optic modulation capability in the crystalline state, and the resonance peak has been coarsely tuned to around 1580 nm through phase transition. Figure 8 As shown in (b), the resonance peak shift between 0V and 3V is approximately 10nm. After the voltage is removed, the spectrum returns to the initial crystalline state, indicating that fine compensation of the target operating point can be achieved through thermo-optical effects on the basis of non-volatile coarse tuning.

[0052] To verify the continuity and consistency of volatile fine-tuning, five repetitive voltage scans (0-3V, 0.1V step) were performed on the amorphous device, and the resonance peak shift was recorded for each scan. The results are as follows: Figure 9 As shown in the figure, the data points represent the average resonant peak shift from five tests, and the error bars represent the standard deviation. The overall small error bars indicate that the device exhibits good repeatability. After fitting the data points with a quadratic term, the fitted curve closely matches the typical pattern of the thermo-optic effect (modulation is quadratically related to voltage), confirming the reliability of the thermo-optic modulation mechanism. Furthermore, by reducing the voltage change step size and optimizing the noise suppression capability of the circuit system, the modulation order can be further improved, achieving higher precision optical field modulation.

[0053] This embodiment fully verifies the technical feasibility of the present invention through the structural design, fabrication, and performance testing of SbSe-based electrically controlled metasurface devices.

[0054] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0055] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A chalcogenide phase-change super-structured surface spatial light multi-order modulation device based on phase change-thermal light synergistic effect, characterized in that, From bottom to top, it includes a microthermal electrode module (1) and a metasurface module (2); The microthermal electrode module (1) can generate heat through the resistive heating effect and transfer the heat to the phase change material functional layer; The metasurface module (2) includes a modulation function layer (23), a metasurface structure, and uses a chalcogenide phase change material to achieve modulation function. It can realize the change of refractive index of the phase change material and the modulation of the light field through phase change and / or thermo-optic effect. Among them, the micro-thermal electrode module (1) can use high-voltage electric pulses to heat the control function layer (23) to trigger the phase change material to achieve phase change of different degrees, thereby achieving non-volatile coarse adjustment; the micro-thermal electrode module (1) can use low-voltage pulses to heat the control function layer (23) and use the thermo-optic effect of the phase change material to achieve volatile fine adjustment. The low-voltage pulse does not trigger the phase change of the phase change material, and the temperature is lower than the crystallization temperature of the phase change material.

2. The spatial light multi-stage modulation device for chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 1, characterized in that, The microthermal electrode module (1) comprises, from bottom to top: Substrate (11); Heating electrode (12) is used to generate heat through resistive heating effect and transfer heat to the phase change material functional layer; The electrode lead layer (13) is used to make two contacts with the heating electrode (12) and extend outward to connect with the external control current; An insulating layer (14) is used to isolate the heating electrode (12) from the air and the metasurface.

3. The spatial light multi-stage modulation device for chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 2, characterized in that, The heating electrode (12) is made of a metal or a transparent conductive oxide, and the size of the heating electrode (12) is larger than that of the phase change material layer; the electrode lead layer (13) is made of a metal; and the insulating layer (14) is made of aluminum oxide or silicon oxide.

4. The spatial light multi-stage modulation device for chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 1, characterized in that, The metasurface module (2) comprises, from bottom to top: Metal reflective layer (21); A dielectric isolation layer (22) is used to isolate the metasurface resonant mode field from the metal reflective layer (21); Regulation function layer (23); A dielectric protective layer (24) is used to isolate air and regulate the functional layer (23).

5. The spatial light multi-stage modulation device for chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 1, characterized in that, The metasurface includes an array of micro- and nanostructures, which may include cylindrical, square, negative cylindrical, negative square, or topological columnar structures. The longitudinal thickness of the micro- and nanostructures is any choice less than the target wavelength, and the lateral dimension is any choice less than the metasurface period.

6. The spatial light multi-stage modulation device for chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 1, characterized in that, The phase change material includes Ge2Sb2Te5, Ge2Sb2Se4Te1, Sb2Se3, or Sb2S3.

7. The spatial light multi-stage modulation device for chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 4, characterized in that, The metal reflective layer (21) is made of a metal material that can provide high reflectivity to the target wavelength, including gold, aluminum, titanium or platinum; the thickness of the metal reflective layer (21) is any choice that can provide high reflectivity to the target wavelength; high reflectivity means reflectivity greater than 90%; the dielectric isolation layer (22) is made of aluminum oxide or silicon oxide, and the thickness of the dielectric isolation layer (22) is any choice that is less than the target wavelength; the dielectric protective layer (24) is made of aluminum oxide or silicon oxide, and the thickness of the dielectric protective layer (24) is any choice that is less than the target wavelength.

8. A method for multi-level spatial light modulation of chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effects, characterized in that, The apparatus according to any one of claims 1 to 7 comprises the following steps: Non-volatile coarse adjustment: Apply a high-voltage electrical pulse to the micro-thermal electrode module (1) to heat the control functional layer (23) and trigger the phase change material to achieve phase change of different degrees, thereby achieving non-volatile coarse adjustment; Volatility fine-tuning: Apply low-voltage pulse heating control layer (23) to micro-thermal electrode module (1) to achieve volatile fine-tuning by utilizing the thermo-optic effect of phase change material. The low-voltage pulse does not trigger phase change of phase change material and the temperature is lower than the crystallization temperature of phase change material.

9. The method for multi-level spatial light modulation of chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 8, characterized in that, During non-volatile coarse tuning, a high-voltage electrical pulse is applied to heat the phase change material to its crystallization temperature, causing crystallization, or to its melting temperature, causing decrystallization. Different degrees of crystallization are achieved by controlling the voltage, roughly locating the target modulation state. During volatile fine tuning, the non-volatility of the phase change material is considered to set an initial static operating point for the device. Then, a low-voltage pulse is applied to heat the phase change material, increasing its temperature without changing the static operating point. The thermo-optic effect of the phase change material is used for small-range, continuous, and dynamic fine tuning to accurately compensate for deviations and bring the device to the target modulation state. During volatile fine tuning, the low-voltage pulse can be maintained or stopped as needed.

10. The method for multi-level spatial light modulation of chalcogenide phase change metasurfaces based on phase change-thermo-optic synergistic effect according to claim 8, characterized in that, It also includes controlling the optical parameters of incident spatial light by changing the hierarchy of metasurface structures or the size or shape of micro / nano structure arrays, wherein the optical parameters include amplitude, phase, and polarization.

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