A method and system for fabricating an all-optical polarization switch

Abstract

This application provides a method and system for fabricating an all-optical polarization switch. The method includes: obtaining the performance requirements of the polarization switch, which are the corresponding indicators of the polarization switch for the transmission, reflection, or absorption of various types of polarized light; constructing an initial simulation model based on preset parameters, wherein the initial simulation model is an intrinsic chiral resonant silicon-based metasurface composed of several basic units, each basic unit including an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film; adjusting the preset parameters of the initial simulation model according to the performance requirements using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model; and fabricating the all-optical polarization switch using micro-nano fabrication processes based on the polarization switch simulation model, thereby improving the spectral range and response speed of the polarization switch.

Description

Technical Field

[0001] This application relates to the field of all-optical polarization modulation technology, and in particular to a method and system for fabricating an all-optical polarization switch. Background Technology

[0002] All-optical polarization modulation refers to modulating the polarization state of light without the need for additional photoelectric conversion, thereby increasing the modulation speed. All-optical polarization switching in the visible light band is still relatively rare, and most methods are based on plasma effects. Achieving rapid modulation of light polarization on a sub-picosecond scale would revolutionize fields such as optical communication, quantum computing, biological detection, and chemistry.

[0003] Chiral response refers to the difference in transmission, reflection, or absorption between left-handed and right-handed circularly polarized light after passing through a structure. Intrinsic chiral response is the chiral response generated when the angle between the light and the interface normal is 0°. Generating intrinsic chiral response can result in a much larger proportion of reflected left-handed or right-handed circularly polarized light, or vice versa. By designing high-quality factor chiral resonances using silicon-based metasurfaces, and introducing ultrafast refractive index changes through free carriers in silicon, the ratio of reflected to transmitted right-handed and left-handed circularly polarized light can be altered, thus achieving ultrafast polarization switching. Most current ultrafast polarization switches have weak chiral responses and are not intrinsic chiral responses, meaning the incident light does not have a 0° angle with the incident interface normal, increasing the difficulty of adjusting the light angle in practical applications. While some ultrafast polarization switches employ intrinsic chiral resonances, the fabrication of composite metasurfaces is more complex, and they operate in the mid-infrared band, limiting their practical applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a method and system for fabricating an all-optical polarization switch, thereby improving the band application range and response speed of the polarization switch.

[0005] In a first aspect, embodiments of this application provide a method for fabricating an all-optical polarization switch, comprising:

[0006] Obtain the performance requirements of the polarization switch, wherein the performance requirements are the corresponding indicators of the polarization switch for the transmission, reflection or absorption of various types of polarized light;

[0007] An initial simulation model is constructed based on preset parameters. The initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of several basic units. Each basic unit includes an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film.

[0008] Based on the performance requirements, the preset parameters of the initial simulation model are adjusted using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining the polarization switch simulation model.

[0009] Based on the polarization switch simulation model, the all-optical polarization switch was fabricated using micro-nano fabrication processes.

[0010] This application provides a method for fabricating an all-optical polarization switch. By constructing a simulation model and using simulation calculations to determine various parameters of the polarization switch simulation model, this application allows for the fabrication of corresponding all-optical polarization switches based on performance requirements, improving the efficiency and accuracy of all-optical polarization switch fabrication. Furthermore, the all-optical polarization switch fabricated in this application is an intrinsically chiral resonant silicon-based metasurface. Intrinsic chiral resonance is achieved through an arrangement of silicon elliptical cylinders on an amorphous silicon thin film, improving the applicability and response speed of the polarization switch. Specifically, during the use of the all-optical polarization switch, it can be excited by pump light. The pump light is incident on the silicon-based resonant cavity, exciting the carrier dynamics and causing a rapid change in the refractive index of the amorphous silicon. When the refractive index of silicon changes, the chiral resonance shifts, thereby achieving a rapid polarization response. Moreover, the all-optical polarization switch operates in the visible light band, improving the band applicability and response speed of the polarization switch.

[0011] In one possible implementation, constructing the initial simulation model based on preset parameters includes:

[0012] Two silicon elliptical cylinders in each of the basic units are placed upright on the corresponding amorphous silicon thin film based on a preset geometric center distance, and the major axes of the ellipses of each silicon elliptical cylinder are parallel to each other.

[0013] A three-dimensional rectangular coordinate system xyz is established for each basic unit, wherein the plane constructed by the x-axis and y-axis is parallel to the plane where the amorphous silicon thin film is located, and the y-axis is parallel to the major axis of the ellipse.

[0014] Based on the major axis of the ellipse, the two silicon elliptical cylinders in each of the basic units are rotated in opposite directions by a preset rotation angle.

[0015] The two silicon elliptical cylinders in each of the basic units are tilted at a preset tilt angle in the x-axis direction;

[0016] Periodic boundary conditions are set for each of the basic units in the x and y directions;

[0017] Two matching layers are set in the z-direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon thin film and the other matching layer is located above the two silicon elliptical cylinders;

[0018] The basic units are arranged along the x-axis to construct the initial simulation model.

[0019] Furthermore, adjusting the preset parameters of the initial simulation model using the finite element method according to the performance requirements until the initial simulation model meets the performance requirements includes:

[0020] The initial simulation model is irradiated with pre-defined polarized light, and the corresponding reflected light is obtained.

[0021] The polarization spectrum of the reflected light is calculated.

[0022] Determine whether the initial simulation model meets the performance requirements based on the polarization spectrum;

[0023] If the performance requirements are not met, the tilt angle and rotation angle of each silicon elliptical cylinder in the initial simulation model are adjusted by the finite element method, and the corresponding polarization spectrum is recalculated until the initial simulation model meets the performance requirements, thus obtaining the polarization switch simulation model.

[0024] This application provides a method for constructing an initial simulation model and adjusting its parameters. By rotating two silicon elliptical cylinders relative to each other and tilting them along the x-axis, the initial simulation model acquires intrinsic chiral resonance capability. In practical applications, polarization switches have various performance requirements, necessitating different tilt and rotation angles. Therefore, this application combines simulation calculation methods to determine the parameters of the initial simulation model in a virtual simulation environment, obtaining a polarization switch simulation model. Based on this model, a corresponding all-optical polarization switch is then fabricated. Thus, this application allows for the flexible fabrication of all-optical polarization switches with different performance characteristics, enabling the final fabricated polarization switch to achieve different left-hand and right-hand circular polarization ratios, thereby improving the flexibility of all-optical polarization switch fabrication.

[0025] In one possible implementation, the preset parameters include the finite element method calculation period, the major and minor axes of the silicon elliptical cylinder, the distance between the geometric centers of two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle of the silicon elliptical cylinder, and the tilt angle.

[0026] In this embodiment of the application, by presetting the values ​​of some model parameters, an initial simulation model can be quickly constructed based on the preset parameters each time an all-optical polarization switch is fabricated. Furthermore, the initial simulation model already possesses a certain intrinsic chiral resonance capability, providing a model basis for subsequent simulation calculations and parameter adjustments, thereby improving the fabrication efficiency of the all-optical polarization switch.

[0027] In one possible implementation, during the fabrication of the all-optical polarization switch using micro-nano fabrication processes, a tilting etching process is used to etch the silicon sample on the amorphous silicon thin film according to the tilt angle of each silicon elliptical cylinder in the polarization switch simulation model, thereby obtaining each silicon elliptical cylinder with a tilt angle.

[0028] This application provides an etching method corresponding to the structure of the all-optical polarization switch provided in this application. In the prior art, intrinsic chiral resonant silicon-based metasurfaces are generally vertical structures, while in this application, the silicon elliptical cylinder is tilted at a certain angle in its structural design. Therefore, the intrinsic chiral resonant silicon-based metasurface provided in this application is a tilted structure. During the fabrication process using micro-nano fabrication technology, a tilted etching process is required to ensure that the final fabricated all-optical polarization switch is structurally consistent with the polarization switch simulation model, thereby improving the accuracy of the all-optical polarization switch fabrication.

[0029] On the other hand, correspondingly, embodiments of this application provide a fabrication system for an all-optical polarization switch, including an acquisition module, a model building module, a simulation calculation module, and a fabrication module;

[0030] The acquisition module is used to acquire the performance requirements of the polarization switch, which are the corresponding indicators of the polarization switch for the transmission, reflection or absorption of various types of polarized light.

[0031] The model building module is used to build an initial simulation model according to preset parameters. The initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of several basic units. Each basic unit includes an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film.

[0032] The simulation calculation module is used to adjust the preset parameters of the initial simulation model according to the performance requirements using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model.

[0033] The fabrication module is used to fabricate the all-optical polarization switch using micro-nano fabrication processes based on the polarization switch simulation model.

[0034] In one possible implementation, the model building module constructs an initial simulation model based on preset parameters, including:

[0035] Two silicon elliptical cylinders in each of the basic units are placed upright on the corresponding amorphous silicon thin film based on a preset geometric center distance, and the major axes of the ellipses of each silicon elliptical cylinder are parallel to each other.

[0036] A three-dimensional rectangular coordinate system xyz is established for each basic unit, wherein the plane constructed by the x-axis and y-axis is parallel to the plane where the amorphous silicon thin film is located, and the y-axis is parallel to the major axis of the ellipse.

[0037] Based on the major axis of the ellipse, the two silicon elliptical cylinders in each of the basic units are rotated in opposite directions by a preset rotation angle.

[0038] The two silicon elliptical cylinders in each of the basic units are tilted at a preset tilt angle in the x-axis direction;

[0039] Periodic boundary conditions are set for each of the basic units in the x and y directions;

[0040] Two matching layers are set in the z-direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon thin film and the other matching layer is located above the two silicon elliptical cylinders;

[0041] The basic units are arranged along the x-axis to construct the initial simulation model.

[0042] Furthermore, the simulation calculation module adjusts the preset parameters of the initial simulation model using the finite element method according to the performance requirements until the initial simulation model meets the performance requirements, including:

[0043] The initial simulation model is irradiated with pre-defined polarized light, and the corresponding reflected light is obtained.

[0044] The polarization spectrum of the reflected light is calculated.

[0045] Determine whether the initial simulation model meets the performance requirements based on the polarization spectrum;

[0046] If the performance requirements are not met, the tilt angle and rotation angle of each silicon elliptical cylinder in the initial simulation model are adjusted by the finite element method, and the corresponding polarization spectrum is recalculated until the initial simulation model meets the performance requirements, thus obtaining the polarization switch simulation model.

[0047] In one possible implementation, the preset parameters include the finite element method calculation period, the major and minor axes of the silicon elliptical cylinder, the distance between the geometric centers of two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle of the silicon elliptical cylinder, and the tilt angle.

[0048] In one possible implementation, during the fabrication of the all-optical polarization switch using micro-nano fabrication processes in the fabrication module, a tilting etching process is used to etch the silicon sample on the amorphous silicon thin film according to the tilt angle of each silicon elliptical cylinder in the polarization switch simulation model, thereby obtaining each silicon elliptical cylinder with a tilt angle. Attached Figure Description

[0049] Figure 1 This is a schematic flowchart illustrating a method for fabricating an all-optical polarization switch according to an embodiment of this application.

[0050] Figure 2 : Front view of the initial simulation model of a method for fabricating an all-optical polarization switch provided in this application embodiment.

[0051] Figure 3 : This is a schematic diagram of the initial state of the initial simulation model of a method for fabricating an all-optical polarization switch provided in this application embodiment.

[0052] Figure 4 : A schematic diagram of the rotation of an elliptical cylinder for the initial simulation model of a method for fabricating an all-optical polarization switch provided in this application embodiment.

[0053] Figure 5 : A schematic diagram of the tilted elliptical cylinder of the initial simulation model of a method for fabricating an all-optical polarization switch provided in this application embodiment.

[0054] Figure 6 This is a polarization spectrum diagram during the simulation calculation process of a method for fabricating an all-optical polarization switch provided in this application embodiment.

[0055] Figure 7 : A schematic diagram of the initial simulation model of a method for fabricating an all-optical polarization switch provided in this application embodiment.

[0056] Figure 8 This is a schematic diagram of the fabrication process in a method for fabricating an all-optical polarization switch provided in an embodiment of this application.

[0057] Figure 9 This is a schematic diagram of the polarization process of an all-optical polarization switch in a method for fabricating an all-optical polarization switch provided in an embodiment of this application.

[0058] Figure 10 : A schematic diagram of the experimental apparatus used to verify the performance of a polarization switch in a method for fabricating an all-optical polarization switch provided in an embodiment of this application.

[0059] Figure 11 This is a schematic diagram of an experimental result from a method for fabricating an all-optical polarization switch provided in an embodiment of this application.

[0060] Figure 12 This is a schematic diagram showing the switching ratio of an all-optical polarization switch in a method for fabricating an all-optical polarization switch provided in this application.

[0061] Figure 13 : A schematic diagram of the fabrication system of an all-optical polarization switch provided in an embodiment of this application. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0063] It should be noted that the step numbers in this document are only for the convenience of explaining the specific embodiments and are not intended to limit the order in which the steps are performed. In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0064] Example 1:

[0065] like Figure 1 As shown, Example 1 provides a method for fabricating an all-optical polarization switch, including steps S1-S4:

[0066] Step S1: Obtain the performance requirements of the polarization switch, wherein the performance requirements are the corresponding indicators of the polarization switch for the transmission, reflection or absorption of various types of polarized light;

[0067] Step S2: Construct an initial simulation model according to preset parameters. The initial simulation model is an intrinsic chiral resonance silicon-based metasurface, which is composed of several basic units. Each basic unit includes an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film.

[0068] Step S3: According to the performance requirements, adjust the preset parameters of the initial simulation model using the finite element method until the initial simulation model meets the performance requirements, and obtain the polarization switch simulation model;

[0069] Step S4: Based on the polarization switch simulation model, the all-optical polarization switch is fabricated using micro-nano fabrication technology.

[0070] This application provides a method for fabricating an all-optical polarization switch. By constructing a simulation model and using simulation calculations to determine various parameters of the polarization switch simulation model, this application allows for the fabrication of corresponding all-optical polarization switches based on performance requirements, improving the efficiency and accuracy of all-optical polarization switch fabrication. Furthermore, the all-optical polarization switch fabricated in this application is an intrinsically chiral resonant silicon-based metasurface. Intrinsic chiral resonance is achieved through an arrangement of silicon elliptical cylinders on an amorphous silicon thin film, improving the applicability and response speed of the polarization switch. Specifically, during the use of the all-optical polarization switch, it can be excited by pump light. The pump light is incident on the silicon-based resonant cavity, exciting the carrier dynamics and causing a rapid change in the refractive index of the amorphous silicon. When the refractive index of silicon changes, the chiral resonance shifts, thereby achieving a rapid polarization response. Moreover, the all-optical polarization switch operates in the visible light band, improving the band applicability and response speed of the polarization switch.

[0071] In one possible implementation, step S2, which involves constructing the initial simulation model based on preset parameters, includes:

[0072] Two silicon elliptical cylinders in each of the basic units are placed upright on the corresponding amorphous silicon thin film based on a preset geometric center distance, and the major axes of the ellipses of each silicon elliptical cylinder are parallel to each other.

[0073] A three-dimensional rectangular coordinate system xyz is established for each basic unit, wherein the plane constructed by the x-axis and y-axis is parallel to the plane where the amorphous silicon thin film is located, and the y-axis is parallel to the major axis of the ellipse.

[0074] Based on the major axis of the ellipse, the two silicon elliptical cylinders in each of the basic units are rotated in opposite directions by a preset rotation angle.

[0075] The two silicon elliptical cylinders in each of the basic units are tilted at a preset tilt angle in the x-axis direction;

[0076] Periodic boundary conditions are set for each of the basic units in the x and y directions;

[0077] Two matching layers are set in the z-direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon thin film and the other matching layer is located above the two silicon elliptical cylinders;

[0078] The basic units are arranged along the x-axis to construct the initial simulation model.

[0079] In a preferred embodiment, the main view of the initial simulation model is as follows: Figure 2As shown, perfectly matched layers are set above and below the z-axis to absorb waves radiated from the simulation region, preventing electromagnetic waves from being reflected and affecting the simulation results. Periodic boundary conditions are set in the x and y directions. The substrate material is silicon oxide with a refractive index of 1.5. To ensure the symmetry of the structure, the refractive index of the top layer is also set to 1.5 for refractive index matching. In the experiment, PMMA can be spin-coated as the refractive index matching layer under negative pressure by placing the sample in a glove box.

[0080] Furthermore, a schematic diagram illustrating the process of rotating and tilting the two silicon elliptical cylinders according to preset rotation and tilt angles is shown below. Figures 3-5 As shown. Among them, Figure 3 The initial state of two silicon elliptical cylinders in a basic unit is determined by the preset parameters: period p, major axis l, minor axis s, distance d between the geometric centers of the two ellipses in the plane, and height h of the elliptical cylinders. The designed resonance mode is around 700nm. Then, by changing the tilt angle and rotation angle in the middle and right steps of the figure below, the designed resonance mode is made to be intrinsic chiral resonance. Figure 4 This is a schematic diagram showing the state of two silicon elliptical cylinders after being rotated in opposite directions by a preset rotation angle β based on the major axis of the ellipse. Figure 5 This is a schematic diagram showing the state of two silicon elliptical cylinders after being tilted at a preset tilt angle θ in the x-axis direction.

[0081] Furthermore, in step S3, adjusting the preset parameters of the initial simulation model using the finite element method according to the performance requirements until the initial simulation model meets the performance requirements includes:

[0082] The initial simulation model is irradiated with pre-defined polarized light, and the corresponding reflected light is obtained.

[0083] The polarization spectrum of the reflected light is calculated.

[0084] Determine whether the initial simulation model meets the performance requirements based on the polarization spectrum;

[0085] If the performance requirements are not met, the tilt angle and rotation angle of each silicon elliptical cylinder in the initial simulation model are adjusted by the finite element method, and the corresponding polarization spectrum is recalculated until the initial simulation model meets the performance requirements, thus obtaining the polarization switch simulation model.

[0086] This application provides a method for constructing an initial simulation model and adjusting its parameters. By rotating two silicon elliptical cylinders relative to each other and tilting them along the x-axis, the initial simulation model acquires intrinsic chiral resonance capability. In practical applications, polarization switches have various performance requirements, necessitating different tilt and rotation angles. Therefore, this application combines simulation calculation methods to determine the parameters of the initial simulation model in a virtual simulation environment, obtaining a polarization switch simulation model. Based on this model, a corresponding all-optical polarization switch is then fabricated. Thus, this application allows for the flexible fabrication of all-optical polarization switches with different performance characteristics, enabling the final fabricated polarization switch to achieve different left-hand and right-hand circular polarization ratios, thereby improving the flexibility of all-optical polarization switch fabrication.

[0087] In a preferred embodiment, when the initial simulation model meets the performance requirements, the spectra of left-handed and right-handed circularly polarized light reflected after normal incidence, calculated using the finite element method, are as follows: Figure 6 As shown. When left-handed circularly polarized light is incident, the reflection opens the left-handed circular polarization channel while closing the right-handed circular polarization channel. R LL R represents the left-handed circularly polarized light reflected from incident left-handed circularly polarized light. LR This represents the right-handed circularly polarized light reflected from the incident left-handed circularly polarized light. The ratio of left-handed to right-handed circularly polarized light is close to 50:1, indicating that the polarization switch simulation model designed in this application successfully suppresses the conversion channel from left-handed to right-handed circularly polarized light.

[0088] In one possible implementation, the preset parameters include the finite element method calculation period, the major and minor axes of the silicon elliptical cylinder, the distance between the geometric centers of two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle of the silicon elliptical cylinder, and the tilt angle.

[0089] In a preferred embodiment, such as Figure 7 As shown, the initial simulation model is designed as an inclined elliptical silicon cylinder. The specific preset parameters of the model are: period p = 400nm, major axis l = 200nm, minor axis s = 100nm, distance d between the geometric centers of the two ellipses in the plane = 180nm, height h of the elliptical cylinder = 205nm, rotation angles of the two elliptical cylinders = β and -β, β = 23°, and tilt angle θ = 10°.

[0090] In this embodiment of the application, by presetting the values ​​of some model parameters, an initial simulation model can be quickly constructed based on the preset parameters each time an all-optical polarization switch is fabricated. Furthermore, the initial simulation model already possesses a certain intrinsic chiral resonance capability, providing a model basis for subsequent simulation calculations and parameter adjustments, thereby improving the fabrication efficiency of the all-optical polarization switch.

[0091] In one possible implementation, during step S4, in the process of fabricating the all-optical polarization switch using micro-nano fabrication technology, the silicon sample on the amorphous silicon thin film is etched using a tilting etching process according to the tilt angle of each silicon elliptical cylinder in the polarization switch simulation model, to obtain each silicon elliptical cylinder with a tilt angle.

[0092] This application provides an etching method corresponding to the structure of the all-optical polarization switch provided in this application. In the prior art, intrinsic chiral resonant silicon-based metasurfaces are generally vertical structures, while in this application, the silicon elliptical cylinder is tilted at a certain angle in its structural design. Therefore, the intrinsic chiral resonant silicon-based metasurface provided in this application is a tilted structure. During the fabrication process using micro-nano fabrication technology, a tilted etching process is required to ensure that the final fabricated all-optical polarization switch is structurally consistent with the polarization switch simulation model, thereby improving the accuracy of the all-optical polarization switch fabrication.

[0093] In a preferred embodiment, the fabrication process of the all-optical polarization switch is as follows: Figure 8 As shown, the all-optical polarization switch was fabricated according to standard micro / nano fabrication processes. First, the surface of the silicon thin film was cleaned, followed by photoresist patterning, electron beam lithography, and development to form a photoresist pattern on the silicon thin film. Then, electron beam evaporation was used to... Cr is deposited onto the sample at a high speed as a mask. The sample is then placed in a stripping solution at room temperature for 12 hours and on an 80°C heating stage for 1 hour. Afterward, the sample is stripped using an acetone gun to form the chromium mask pattern. Excess acetone and stripping solution are then washed away with isopropanol and dried. Next, a reactive ion etching (RIE) machine is used to etch the sample using the previously employed tilting etching process. Before etching, the tilting etching direction and the orientation of the chromium pattern must be carefully confirmed to ensure that the tilting angle and the direction of breaking the symmetry within the structural plane are consistent. The Faraday cage containing the sample is then placed into the RIE chamber for tilting etching. Finally, the sample is immersed in a chromium removal solution for approximately 5 minutes to remove residual chromium. The sample is then removed, washed with deionized water to remove any remaining chromium removal solution, and dried with a nitrogen gun to obtain the all-optical polarization switch.

[0094] In a preferred embodiment, the polarization process of the all-optical polarization switch is as follows: Figure 9As shown, the all-optical polarization switch is constructed based on an intrinsically chiral resonant silicon-based metasurface. The designed resonant mode is around 700 nm. When the all-optical polarization switch is not excited, the reflected light is still left-handed circularly polarized when left-handed circularly polarized light is incident. Figure 9 As shown on the left, when a 400nm pump light is incident on a silicon-based resonant cavity, it excites the carrier dynamics, causing a rapid change in the refractive index of the amorphous silicon. This change in silicon's refractive index leads to a shift in the chiral resonance, resulting in phenomena such as... Figure 9 The effect shown on the right is that, when left-handed circularly polarized light is incident, the reflected light contains both right-handed and left-handed circularly polarized light. Therefore, it can be summarized that the polarization of the reflected light from the chiral resonant metasurface changes extremely rapidly under the illumination of the pump light. Furthermore, the selection of the pump light requires that the photon energy of the pump light be greater than the bandgap of silicon; therefore, any pump light wavelength less than 750 nm can be used to excite the all-optical polarization switch.

[0095] Furthermore, such as Figure 10 As shown in the figure, this application provides an experimental apparatus and method to verify the performance of the all-optical polarization switch. In the experiment, a supercontinuum pulsed white light is used to detect the spectrum, and a change in refractive index is introduced by pumping nonlinear carriers with 400nm light. As shown in the figure below, M is a reflector, BS is a beam splitter, L is a lens, ATT is an attenuator, Filter is a filter, and DL is a delay line. An 800nm ​​femtosecond light is split into two beams: one beam passes through a BBO crystal to generate a 400nm pump light, and the other beam passes through the delay line and is focused onto water to generate pulsed white light. The pulsed white light and the 400nm pump light are jointly focused onto the metasurface to measure the instantaneous polarization of the sample.

[0096] Experimental results are as follows Figure 11 and Figure 12 As shown, where, Figure 11 This diagram illustrates the changes in reflectivity under different delay times. Figure 12This diagram illustrates the on / off ratio of the all-optical polarization switch provided in this application. When the delay time is -0.8 ps, the overlap between the pump and probe light is very small, resulting in almost entirely left-handed circularly polarized light, with a left-handed to right-handed circularly polarized light ratio of 23.6. When the relative delay time is 0 ps, ​​the overlap between the pump and probe light reaches its maximum, maximizing the change in nonlinear refractive index caused by the pump light. Consequently, the transmission spectrum simultaneously contains both left-handed and right-handed circularly polarized components, transforming the transient transmission spectrum from circularly polarized to elliptically polarized light, with a left-handed to right-handed circularly polarized light ratio of 4.23. Therefore, the pump-probe system successfully characterized the change in reflectivity of the intrinsic chiral resonant structure with the pump light and pulse time delay, and analyzed the process of this change. Within 0.8 ps, when the pump light excites the carriers in the structure to generate a nonlinear refractive index, the left-handed circularly polarized component of the reflected light decreases while the right-handed circularly polarized component increases, resulting in an ultrafast change in the polarization of the reflected light.

[0097] Example 2:

[0098] On the other hand, correspondingly, such as Figure 13 As shown, this application provides a fabrication system for an all-optical polarization switch, including an acquisition module 10, a model building module 20, a simulation calculation module 30, and a fabrication module 40.

[0099] The acquisition module 10 is used to acquire the performance requirements of the polarization switch, which are the corresponding indicators of the polarization switch for the transmission, reflection or absorption of various types of polarized light.

[0100] The model building module 20 is used to build an initial simulation model according to preset parameters. The initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of several basic units. Each basic unit includes an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film.

[0101] The simulation calculation module 30 is used to adjust the preset parameters of the initial simulation model according to the performance requirements using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model.

[0102] The fabrication module 40 is used to fabricate the all-optical polarization switch using micro-nano fabrication processes based on the polarization switch simulation model.

[0103] In one possible implementation, the model building module 20 builds an initial simulation model based on preset parameters, including:

[0104] Two silicon elliptical cylinders in each of the basic units are placed upright on the corresponding amorphous silicon thin film based on a preset geometric center distance, and the major axes of the ellipses of each silicon elliptical cylinder are parallel to each other.

[0105] A three-dimensional rectangular coordinate system xyz is established for each basic unit, wherein the plane constructed by the x-axis and y-axis is parallel to the plane where the amorphous silicon thin film is located, and the y-axis is parallel to the major axis of the ellipse.

[0106] Based on the major axis of the ellipse, the two silicon elliptical cylinders in each of the basic units are rotated in opposite directions by a preset rotation angle.

[0107] The two silicon elliptical cylinders in each of the basic units are tilted at a preset tilt angle in the x-axis direction;

[0108] Periodic boundary conditions are set for each of the basic units in the x and y directions;

[0109] Two matching layers are set in the z-direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon thin film and the other matching layer is located above the two silicon elliptical cylinders;

[0110] The basic units are arranged along the x-axis to construct the initial simulation model.

[0111] Furthermore, the simulation calculation module 30 adjusts the preset parameters of the initial simulation model using the finite element method according to the performance requirements until the initial simulation model meets the performance requirements, including:

[0112] The initial simulation model is irradiated with pre-defined polarized light, and the corresponding reflected light is obtained.

[0113] The polarization spectrum of the reflected light is calculated.

[0114] Determine whether the initial simulation model meets the performance requirements based on the polarization spectrum;

[0115] If the performance requirements are not met, the tilt angle and rotation angle of each silicon elliptical cylinder in the initial simulation model are adjusted by the finite element method, and the corresponding polarization spectrum is recalculated until the initial simulation model meets the performance requirements, thus obtaining the polarization switch simulation model.

[0116] In one possible implementation, the preset parameters include the finite element method calculation period, the major and minor axes of the silicon elliptical cylinder, the distance between the geometric centers of two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle of the silicon elliptical cylinder, and the tilt angle.

[0117] In one possible implementation, during the fabrication of the all-optical polarization switch using micro-nano fabrication processes in the fabrication module 40, the silicon sample on the amorphous silicon thin film is etched using a tilting etching process according to the tilt angle of each silicon elliptical cylinder in the polarization switch simulation model, to obtain each silicon elliptical cylinder with a tilt angle.

[0118] This application provides a fabrication system for an all-optical polarization switch. By constructing a simulation model and using simulation calculations to determine various parameters of the polarization switch simulation model, this application can fabricate corresponding all-optical polarization switches based on the performance requirements of the polarization switch, improving the efficiency and accuracy of all-optical polarization switch fabrication. Furthermore, the all-optical polarization switch fabricated in this application is an intrinsically chiral resonant silicon-based metasurface. Intrinsic chiral resonance is achieved through an arrangement of silicon elliptical cylinder structures on an amorphous silicon thin film, improving the applicability and response speed of the polarization switch. Specifically, during the use of the all-optical polarization switch, it can be excited by pump light. The pump light is incident on the silicon-based resonant cavity, exciting the carrier dynamics and causing a rapid change in the refractive index of the amorphous silicon. When the refractive index of silicon changes, the chiral resonance shifts, thereby achieving a rapid polarization response. Moreover, the all-optical polarization switch operates in the visible light band, improving the band applicability and response speed of the polarization switch.

[0119] For a more detailed explanation of the working principle and procedures of this embodiment, please refer to the relevant description in Embodiment 1.

[0120] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application for those skilled in the art.

Claims

1. A method for fabricating an all-optical polarization switch, characterized in that, include: Obtain the performance requirements of the polarization switch, wherein the performance requirements are the corresponding indicators of the polarization switch for the transmission, reflection or absorption of various types of polarized light; An initial simulation model is constructed based on preset parameters. The initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of several basic units. Each basic unit includes an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film. The preset parameters include the finite element method calculation period, the major axis and minor axis of the silicon elliptical cylinder, the geometric center distance between the two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle of the silicon elliptical cylinder, and the tilt angle. The initial simulation model is constructed based on preset parameters, including: placing two silicon elliptical cylinders in each basic unit in an upright position on the corresponding amorphous silicon thin film based on a preset geometric center distance, with the major axes of the ellipses of the silicon elliptical cylinders parallel to each other; establishing a three-dimensional rectangular coordinate system (xyz) for each basic unit, wherein the plane constructed by the x-axis and y-axis is parallel to the plane of the amorphous silicon thin film, and the y-axis is parallel to the major axis of the ellipse; rotating the two silicon elliptical cylinders in each basic unit in opposite directions by a preset rotation angle based on the major axis of the ellipse; tilting the two silicon elliptical cylinders in each basic unit by a preset tilt angle in the x-axis direction; setting periodic boundary conditions for each basic unit in the x and y directions; setting two matching layers in the z-direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon thin film, and the other matching layer is located above the two silicon elliptical cylinders; arranging the basic units along the x-axis direction to construct the initial simulation model. Based on the performance requirements, the preset parameters of the initial simulation model are adjusted using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining the polarization switch simulation model. Based on the polarization switch simulation model, the all-optical polarization switch was fabricated using micro-nano fabrication processes.

2. A method of fabricating an all-optical polarization switch as claimed in claim 1, characterized in that, The step of adjusting the preset parameters of the initial simulation model using the finite element method according to the performance requirements until the initial simulation model meets the performance requirements includes: The initial simulation model is irradiated with pre-defined polarized light, and the corresponding reflected light is obtained. The polarization spectrum of the reflected light is calculated. Determine whether the initial simulation model meets the performance requirements based on the polarization spectrum; If the performance requirements are not met, the tilt angle and rotation angle of each silicon elliptical cylinder in the initial simulation model are adjusted by the finite element method, and the corresponding polarization spectrum is recalculated until the initial simulation model meets the performance requirements, thus obtaining the polarization switch simulation model.

3. A method of fabricating an all-optical polarization switch as claimed in claim 1, characterized in that, In the process of fabricating the all-optical polarization switch using micro-nano fabrication technology, according to the tilt angle of each silicon elliptical cylinder in the polarization switch simulation model, a tilt etching process is used to etch the silicon sample on the amorphous silicon thin film to obtain each silicon elliptical cylinder with a tilt angle.

4. A system for fabricating an all-optical polarization switch, characterized by It includes an acquisition module, a model building module, a simulation calculation module, and a preparation module; The acquisition module is used to acquire the performance requirements of the polarization switch, which are the corresponding indicators of the polarization switch for the transmission, reflection or absorption of various types of polarized light. The model building module is used to build an initial simulation model based on preset parameters. The initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of several basic units. Each basic unit includes an amorphous silicon thin film and two silicon elliptical cylinders located on the amorphous silicon thin film. The preset parameters include the finite element method calculation period, the major axis and minor axis of the silicon elliptical cylinder, the geometric center distance between the two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle of the silicon elliptical cylinder, and the tilt angle. The model building module constructs an initial simulation model based on preset parameters, including: placing two silicon elliptical cylinders in each basic unit in an upright position on the corresponding amorphous silicon thin film based on a preset geometric center distance, with the major axes of the ellipses of each silicon elliptical cylinder parallel to each other; establishing a three-dimensional rectangular coordinate system (xyz) for each basic unit, wherein the plane constructed by the x-axis and y-axis is parallel to the plane of the amorphous silicon thin film, and the y-axis is parallel to the major axis of the ellipse; rotating the two silicon elliptical cylinders in each basic unit in opposite directions by a preset rotation angle based on the major axis of the ellipse; tilting the two silicon elliptical cylinders in each basic unit by a preset tilt angle in the x-axis direction; setting periodic boundary conditions for each basic unit in the x and y directions; setting two matching layers in the z-direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon thin film, and the other matching layer is located above the two silicon elliptical cylinders; arranging each basic unit along the x-axis direction to construct the initial simulation model. The simulation calculation module is used to adjust the preset parameters of the initial simulation model according to the performance requirements using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model. The fabrication module is used to fabricate the all-optical polarization switch using micro-nano fabrication processes based on the polarization switch simulation model.

5. A system for fabricating an all-optical polarization switch as claimed in claim 4, characterized in that The simulation calculation module adjusts the preset parameters of the initial simulation model using the finite element method according to the performance requirements until the initial simulation model meets the performance requirements, including: The initial simulation model is irradiated with pre-defined polarized light, and the corresponding reflected light is obtained. The polarization spectrum of the reflected light is calculated. Determine whether the initial simulation model meets the performance requirements based on the polarization spectrum; If the performance requirements are not met, the tilt angle and rotation angle of each silicon elliptical cylinder in the initial simulation model are adjusted by the finite element method, and the corresponding polarization spectrum is recalculated until the initial simulation model meets the performance requirements, thus obtaining the polarization switch simulation model.

6. A system for fabricating an all-optical polarization switch as claimed in claim 4, wherein, During the fabrication of the all-optical polarization switch using micro-nano fabrication technology in the fabrication module, the silicon sample on the amorphous silicon thin film is etched using an inclined etching process according to the tilt angle of each silicon elliptical cylinder in the polarization switch simulation model, thereby obtaining each silicon elliptical cylinder with a tilt angle.

Images