Preparation method and system of all-optical polarization switch

Abstract

The invention provides a preparation method and system of an all-optical polarization switch, and the method comprises the steps: obtaining the performance requirements of the polarization switch, and the performance requirements are the corresponding indexes of the polarization switch for the transmission, reflection or absorption of various types of polarized light; an initial simulation model is constructed according to preset parameters, the initial simulation model is an intrinsic chiral resonance silicon-based super-structure surface and is formed by arranging a plurality of basic units, and each basic unit comprises an amorphous silicon film and two silicon elliptic cylinders located on the amorphous silicon film; according to the performance requirements, preset parameters of the initial simulation model are adjusted through a finite element method until the initial simulation model meets the performance requirements, and a polarization switch simulation model is obtained; according to the polarization switch simulation model, the all-optical polarization switch is prepared by using a micro-nano preparation process, and the waveband application range and the response speed of the polarization switch are improved.

Description

Technical Field

[0001] The present application relates to the technical field of all-optical polarization modulation, and in particular to a preparation method and system of an all-optical polarization switch. Background Art

[0002] All-optical polarization modulation refers to the use of light to modulate the polarization state without the need for additional photoelectric conversion, thereby increasing the modulation speed. There are relatively few all-optical polarization switches in the visible light band, and they are mainly based on the plasma effect. If the rapid modulation of light polarization can be achieved on a sub-picosecond scale, it will bring changes to optical communications, quantum computing, biological detection, chemistry and other fields.

[0003] Chiral response refers to the difference in transmission, reflection or absorption between left-handed circularly polarized light and right-handed circularly polarized light after passing through the structure. Intrinsic chiral response is the chiral response generated when the angle between the light and the interface normal is 0°. Producing intrinsic chiral response can make the reflected left-handed circularly polarized light much larger than the right-handed circularly polarized light, or the right-handed circularly polarized light much larger than the left-handed circularly polarized light. By designing chiral resonance with high quality factor using silicon-based metasurfaces, the ratio of reflected or transmitted right-handed circularly polarized light and left-handed circularly polarized light can be changed after introducing ultrafast refractive index changes through free carriers of silicon materials, thereby realizing ultrafast polarization switching. Most of the current ultrafast polarization switches have weak chiral responses and are not intrinsic chiral responses, that is, the incident light is not at an angle of 0° to the normal of the incident interface, which increases the difficulty of adjusting the light angle in practical applications. Although some ultrafast polarization switches use intrinsic chiral resonance, the preparation of composite metasurfaces is more complicated, and they work in the mid-infrared band, with a narrow range of practical applications. Summary of the invention

[0004] In view of the above technical problems, the present application provides a method and system for preparing an all-optical polarization switch to improve the wavelength band application range and response speed of the polarization switch.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing an all-optical polarization switch, comprising:

[0006] Acquire performance requirements of the polarization switch, where the performance requirements are corresponding indicators of transmission, reflection or absorption of the polarization switch for each type of polarized light;

[0007] Constructing an initial simulation model according to preset parameters, wherein the initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of a plurality of basic units arranged, each of which includes an amorphous silicon film and two silicon elliptical cylinders located on the amorphous silicon film;

[0008] According to the performance requirements, adjusting preset parameters of the initial simulation model by a finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model;

[0009] According to the polarization switch simulation model, the all-optical polarization switch is manufactured using a micro-nano manufacturing process.

[0010] The embodiment of the present application provides a method for preparing an all-optical polarization switch. By constructing a simulation model and using a simulation calculation method to determine the various parameters of the polarization switch simulation model, the embodiment of the present application can prepare a corresponding all-optical polarization switch based on the performance requirements of the polarization switch, thereby improving the efficiency and accuracy of the preparation of the all-optical polarization switch. In addition, the all-optical polarization switch prepared by the embodiment of the present application is an intrinsic chiral resonance silicon-based metasurface, which realizes intrinsic chiral resonance through an arranged silicon elliptical cylinder structure on an amorphous silicon film, thereby improving the scope of application and response speed of the polarization switch. Specifically, in the process of using the all-optical polarization switch, the all-optical polarization switch can be excited by pump light, and the pump light will be incident on the silicon-based resonant cavity to excite the dynamics of carriers and cause a rapid change in the refractive index of amorphous silicon. When the refractive index of silicon changes, the chiral resonance will move, thereby achieving a rapid polarization response, and the all-optical polarization switch operates in the visible light band, thereby improving the band application range and response speed of the polarization switch.

[0011] In a possible implementation, constructing an initial simulation model according to preset parameters includes:

[0012] Placing two silicon elliptical cylinders in each of the basic units on the corresponding amorphous silicon film in an upright state based on a preset geometric center distance, and the elliptical major axes of each silicon elliptical cylinder are parallel to each other;

[0013] Establishing an xyz three-dimensional rectangular coordinate system for each of the basic units, wherein the plane constructed by the x-axis and the y-axis is parallel to the plane where the amorphous silicon 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] Tilt the two silicon elliptical cylinders in each of the basic units in the x-axis direction at a preset tilt angle;

[0016] Setting periodic boundary conditions of each of the basic units in the x-direction and the y-direction;

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

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

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

[0020] Using preset polarized light to inject into the initial simulation model, and obtaining corresponding reflected light;

[0021] Calculating and obtaining the polarization spectrum of the reflected light;

[0022] Determining whether the initial simulation model meets the performance requirement according to the polarization spectrum;

[0023] If the performance requirement is not met, the inclination 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 requirement, thereby obtaining the polarization switch simulation model.

[0024] The embodiment of the present application provides a method for constructing an initial simulation model and adjusting model parameters, by rotating two silicon elliptical cylinders relative to each other and tilting them in the x-axis direction, so that the initial simulation model already has the ability of intrinsic chiral resonance. In actual applications, there are various performance requirements for polarization switches, and the required tilt angles and rotation angles are different. Therefore, the embodiment of the present application combines a simulation calculation method, determines the various parameters of the initial simulation model through simulation calculation in a virtual simulation environment, obtains a polarization switch simulation model, and prepares a corresponding all-optical polarization switch according to the polarization switch simulation model. Therefore, the embodiment of the present application can flexibly prepare all-optical polarization switches with different performances according to the needs, so that the polarization switch finally prepared can achieve different left-right circularly polarized light ratios according to the needs, thereby improving the flexibility of the preparation of the all-optical polarization switch.

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

[0026] In the embodiment of the present application, by presetting the values ​​of some model parameters, each time an all-optical polarization switch is prepared, an initial simulation model can be quickly constructed according to the preset parameters, and the initial simulation model already has a certain intrinsic chiral resonance capability, which provides a model basis for subsequent simulation calculations and parameter adjustments, thereby improving the preparation efficiency of the all-optical polarization switch.

[0027] In one possible implementation, in the process of preparing the all-optical polarization switch using a micro-nano preparation process, an inclined etching process is used to etch the silicon sample on the amorphous silicon film according to the inclination angle of each silicon elliptical cylinder in the polarization switch simulation model to obtain silicon elliptical cylinders with inclination angles.

[0028] The embodiment of the present application provides an etching method, which corresponds to the structure of the all-optical polarization switch provided by the embodiment of the present application. In the prior art, the intrinsic chiral resonant silicon-based metasurface is generally a vertical structure, and the embodiment of the present application tilts the silicon elliptical cylinder at a certain angle in the structural design. Therefore, the intrinsic chiral resonant silicon-based metasurface provided by the embodiment of the present application is an inclined structure. In the process of preparation using the micro-nano preparation process, an inclined etching process needs to be used to ensure that the structure of the finally prepared all-optical polarization switch is consistent with the polarization switch simulation model, thereby improving the accuracy of the preparation of the all-optical polarization switch.

[0029] On the other hand, accordingly, an embodiment of the present application provides a system for preparing an all-optical polarization switch, including an acquisition module, a model building module, a simulation calculation module, and a preparation module;

[0030] The acquisition module is used to acquire the performance requirements of the polarization switch, where the performance requirements are corresponding indicators of the transmission, reflection or absorption of each type of polarized light by the polarization switch;

[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 a plurality of basic units arranged, each of which includes an amorphous silicon film and two silicon elliptical cylinders located on the amorphous silicon film;

[0032] The simulation calculation module is used to adjust the preset parameters of the initial simulation model by the finite element method according to the performance requirements, until the initial simulation model meets the performance requirements, so as to obtain a polarization switch simulation model;

[0033] The preparation module is used to prepare the all-optical polarization switch using a micro-nano preparation process according to the polarization switch simulation model.

[0034] In a possible implementation, the model building module builds an initial simulation model according to preset parameters, including:

[0035] Placing two silicon elliptical cylinders in each of the basic units on the corresponding amorphous silicon film in an upright state based on a preset geometric center distance, and the elliptical major axes of each silicon elliptical cylinder are parallel to each other;

[0036] Establishing an xyz three-dimensional rectangular coordinate system for each of the basic units, wherein the plane constructed by the x-axis and the y-axis is parallel to the plane where the amorphous silicon 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] Tilt the two silicon elliptical cylinders in each of the basic units in the x-axis direction at a preset tilt angle;

[0039] Setting periodic boundary conditions of each of the basic units in the x-direction and the y-direction;

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

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

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

[0043] Using preset polarized light to inject into the initial simulation model, and obtaining corresponding reflected light;

[0044] Calculating and obtaining the polarization spectrum of the reflected light;

[0045] Determining whether the initial simulation model meets the performance requirement according to the polarization spectrum;

[0046] If the performance requirement is not met, the inclination 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 requirement, thereby obtaining the polarization switch simulation model.

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

[0048] In one possible implementation, in the process of the preparation module using a micro-nano preparation process to prepare the all-optical polarization switch, an inclined etching process is used to etch the silicon sample on the amorphous silicon film according to the inclination angle of each silicon elliptical cylinder in the polarization switch simulation model to obtain silicon elliptical cylinders with inclination angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 : A schematic flow chart of a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

[0050] Figure 2 : A front view of an initial simulation model of a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

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

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

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

[0054] Figure 6 : A schematic diagram of a polarization spectrum during a simulation calculation process of a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

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

[0056] Figure 8 : A schematic diagram of the preparation process of a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

[0057] Fig. 9 : Schematic diagram of the polarization process of an all-optical polarization switch in a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

[0058] Fig.10 : A schematic diagram of the structure of an experimental device for verifying the performance of a polarization switch in a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

[0059] Fig.11 : A schematic diagram of experimental results in a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

[0060] Fig.12 : A schematic diagram of the switching ratio of an all-optical polarization switch in a method for preparing an all-optical polarization switch provided in an embodiment of the present application.

[0061] Fig.13 : A structural schematic diagram of a system for preparing an all-optical polarization switch provided in an embodiment of the present application. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0063] It should be noted that the step numbers in the text are only for the convenience of explanation of the specific embodiments and do not serve to limit the order in which the steps are executed. In the description of this application, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0064] Embodiment 1:

[0065] like Figure 1 As shown, Embodiment 1 provides a method for preparing an all-optical polarization switch, comprising steps S1-S4:

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

[0067] Step S2, constructing an initial simulation model according to preset parameters, wherein the initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of a plurality of basic units arranged, each of which includes an amorphous silicon film and two silicon elliptical cylinders located on the amorphous silicon film;

[0068] Step S3, according to the performance requirements, adjusting the preset parameters of the initial simulation model by using the finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model;

[0069] Step S4: According to the polarization switch simulation model, the all-optical polarization switch is manufactured using a micro-nano manufacturing process.

[0070] The embodiment of the present application provides a method for preparing an all-optical polarization switch. By constructing a simulation model and using a simulation calculation method to determine the various parameters of the polarization switch simulation model, the embodiment of the present application can prepare a corresponding all-optical polarization switch based on the performance requirements of the polarization switch, thereby improving the efficiency and accuracy of the preparation of the all-optical polarization switch. In addition, the all-optical polarization switch prepared by the embodiment of the present application is an intrinsic chiral resonance silicon-based metasurface, which realizes intrinsic chiral resonance through an arranged silicon elliptical cylinder structure on an amorphous silicon film, thereby improving the scope of application and response speed of the polarization switch. Specifically, in the process of using the all-optical polarization switch, the all-optical polarization switch can be excited by pump light, and the pump light will be incident on the silicon-based resonant cavity to excite the dynamics of carriers and cause a rapid change in the refractive index of amorphous silicon. When the refractive index of silicon changes, the chiral resonance will move, thereby achieving a rapid polarization response, and the all-optical polarization switch operates in the visible light band, thereby improving the band application range and response speed of the polarization switch.

[0071] In a possible implementation, in step S2, constructing an initial simulation model according to preset parameters includes:

[0072] Placing two silicon elliptical cylinders in each of the basic units on the corresponding amorphous silicon film in an upright state based on a preset geometric center distance, and the elliptical major axes of each silicon elliptical cylinder are parallel to each other;

[0073] Establishing an xyz three-dimensional rectangular coordinate system for each of the basic units, wherein the plane constructed by the x-axis and the y-axis is parallel to the plane where the amorphous silicon 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] Tilt the two silicon elliptical cylinders in each of the basic units in the x-axis direction at a preset tilt angle;

[0076] Setting periodic boundary conditions of each of the basic units in the x-direction and the y-direction;

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

[0078] The basic units are arranged along the x-axis direction 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, a perfect matching layer is set up in the z direction to absorb the waves radiated from the region to the outside of the simulation region to prevent the 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, and the refractive index is set to 1.5. In order to ensure the symmetry of the structure, the refractive index of the structure is also set to 1.5 for refractive index matching. In the experiment, the sample can be placed in a glove box and spin-coated with PMMA under negative pressure as a refractive index matching layer.

[0080] Furthermore, a schematic diagram of the process of rotating and tilting the two silicon elliptical cylinders according to the preset rotation angle and the preset tilt angle is shown in FIG. Figure 3-Figure 5 As shown. Among them, Figure 3 This is the initial state of two silicon elliptical cylinders in a basic unit. At this time, the period p, the major axis l of the ellipse, the minor axis s, the geometric center distance d of the two ellipses in the plane, and the height h of the elliptical cylinder are determined according to the preset parameters, so that the designed resonance mode is around 700nm. Next, the tilt angle and rotation angle are changed in two steps in the middle and right of the figure below, so that the designed resonance mode is the intrinsic chiral resonance. Figure 4 Schematic diagram of the state after two silicon elliptical cylinders are rotated in opposite directions by a preset rotation angle β based on the major axis of the ellipse, Figure 5 It is a schematic diagram of the state after two silicon elliptical cylinders are tilted in the x-axis direction by a preset tilt angle θ.

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

[0082] Using preset polarized light to inject into the initial simulation model, and obtaining corresponding reflected light;

[0083] Calculating and obtaining the polarization spectrum of the reflected light;

[0084] Determining whether the initial simulation model meets the performance requirement according to the polarization spectrum;

[0085] If the performance requirement is not met, the inclination 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 requirement, thereby obtaining the polarization switch simulation model.

[0086] The embodiment of the present application provides a method for constructing an initial simulation model and adjusting model parameters, by rotating two silicon elliptical cylinders relative to each other and tilting them in the x-axis direction, so that the initial simulation model already has the ability of intrinsic chiral resonance. In actual applications, there are various performance requirements for polarization switches, and the required tilt angles and rotation angles are different. Therefore, the embodiment of the present application combines a simulation calculation method, determines the various parameters of the initial simulation model through simulation calculation in a virtual simulation environment, obtains a polarization switch simulation model, and prepares a corresponding all-optical polarization switch according to the polarization switch simulation model. Therefore, the embodiment of the present application can flexibly prepare all-optical polarization switches with different performances according to the needs, so that the polarization switch finally prepared can achieve different left-right circularly polarized light ratios according to the needs, thereby improving the flexibility of the preparation of the all-optical polarization switch.

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

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

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

[0090] In the embodiment of the present application, by presetting the values ​​of some model parameters, each time an all-optical polarization switch is prepared, an initial simulation model can be quickly constructed according to the preset parameters, and the initial simulation model already has a certain intrinsic chiral resonance capability, which provides a model basis for subsequent simulation calculations and parameter adjustments, thereby improving the preparation efficiency of the all-optical polarization switch.

[0091] In one possible implementation, in step S4, in the process of preparing the all-optical polarization switch using a micro-nano preparation process, an inclined etching process is used to etch the silicon sample on the amorphous silicon film according to the inclination angle of each silicon elliptical cylinder in the polarization switch simulation model to obtain silicon elliptical cylinders with inclination angles.

[0092] The embodiment of the present application provides an etching method, which corresponds to the structure of the all-optical polarization switch provided by the embodiment of the present application. In the prior art, the intrinsic chiral resonant silicon-based metasurface is generally a vertical structure, and the embodiment of the present application tilts the silicon elliptical cylinder at a certain angle in the structural design. Therefore, the intrinsic chiral resonant silicon-based metasurface provided by the embodiment of the present application is an inclined structure. In the process of preparation using the micro-nano preparation process, an inclined etching process needs to be used to ensure that the structure of the finally prepared all-optical polarization switch is consistent with the polarization switch simulation model, thereby improving the accuracy of the preparation of the all-optical polarization switch.

[0093] In a preferred embodiment, the preparation process of the all-optical polarization switch is as follows: Figure 8 As shown, the all-optical polarization switch is prepared according to the standard micro-nano preparation process. First, the surface of the silicon film is cleaned, and a photoresist pattern is generated on the silicon film after coating, electron beam lithography and development. Then, electron beam evaporation is used to Cr is evaporated onto the sample at a rate as a mask, and then the sample is placed in a stripping solution for 12 hours at room temperature and on a heating table at 80°C for 1 hour. The sample is then purged with an acetone gun for stripping to form a chromium mask pattern, and then the excess acetone and stripping solution are cleaned with isopropyl alcohol and blown dry. The sample is then etched using a reactive ion etcher based on the previous tilted etching process. Before etching, the tilted etching direction and the direction of the chromium pattern must be carefully confirmed to ensure that the direction of the tilt angle is consistent with the direction of breaking the symmetry within the structural surface. The Faraday cage with the sample is then placed in the reactive ion etching chamber for tilted etching. Finally, the sample is immersed in a dechroming solution for about 5 minutes to remove the residual chromium, the sample is taken out and the residual dechroming solution is washed off with deionized water, and the sample is blown dry 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: Fig. 9As shown, the all-optical polarization switch is constructed based on an intrinsic chiral resonant silicon-based metasurface, and the designed resonance mode is around 700nm. 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, as shown in FIG. Fig. 9 As shown on the left. When 400nm pump light is incident on the silicon-based resonant cavity, the dynamics of the carriers are excited, causing the refractive index of amorphous silicon to change rapidly. When the refractive index of silicon changes, the chiral resonance will move, resulting in Fig. 9 The effect shown on the right side shows that when left-handed circularly polarized light is incident, the reflected light contains both right-handed circularly polarized light and left-handed circularly polarized light. Therefore, it can be concluded that the polarization of the light reflected from the chiral resonant metasurface changes ultrafast under the irradiation of the pump light. In addition, for the selection of pump light, the photon energy of the pump light needs to be greater than the forbidden band width of silicon, so the corresponding pump light wavelength less than 750nm can be used to excite the all-optical polarization switch.

[0095] Further, such as Fig.10 As shown, the embodiment of the present application provides an experimental device and an experimental method to verify the performance of the all-optical polarization switch. In the experiment, supercontinuum pulsed white light is used to detect the spectrum, and 400nm light is used to pump nonlinear carriers to introduce changes in the refractive index. 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. The 800nm ​​femtosecond light is divided into two beams, one beam passes through a BBO crystal to generate a 400nm pump light, and the other beam passes through a delay line and is focused into the water to generate pulsed white light. The pulsed white light and the 400nm pump light are focused together onto the metasurface to measure the instantaneous polarization of the sample.

[0096] The experimental results are as follows Fig.11 and Fig.12 As shown, Fig.11 The schematic diagram of reflectivity change under different delay times is shown. Fig.12The schematic diagram of the switch ratio of the all-optical polarization switch provided in the embodiment of the present application is shown. When the delay time is -0.8ps, since the range of the overlap of the pump light and the detection light in time is very small, the reflected light is almost entirely left-handed circularly polarized light, and the ratio of left-handed circularly polarized light to right-handed circularly polarized light is 23.6. When the relative delay time is 0ps, since the range of the overlap of the pump light and the detection light in time reaches the maximum, as the change of the nonlinear refractive index brought by the pump light reaches the maximum, the corresponding transmission spectrum simultaneously has two components of left-handed circular polarization and right-handed circular polarization, so the transient transmission spectrum is transformed from circularly polarized light to elliptically polarized light, and the ratio of left-handed circularly polarized light to right-handed circularly polarized light is 4.23. Therefore, the change of the reflectivity of the intrinsic chiral resonant structure with the time delay of the pump light and the pulse light is successfully characterized by the pump-detection system, and the change process is analyzed. In the 0.8ps when the carriers of the pump light excite the structure to generate the nonlinear refractive index, the reflected left-handed circularly polarized component decreases and the right-handed circularly polarized component increases, and the polarization of the reflected light achieves an ultrafast change.

[0097] Embodiment 2:

[0098] On the other hand, correspondingly, Fig.13 As shown, the embodiment of the present application provides a system for preparing an all-optical polarization switch, including an acquisition module 10, a model building module 20, a simulation calculation module 30 and a preparation module 40;

[0099] The acquisition module 10 is used to acquire the performance requirements of the polarization switch, where the performance requirements are corresponding indicators of the transmission, reflection or absorption of each type of polarized light by the polarization switch;

[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 a plurality of basic units arranged, each of which includes an amorphous silicon film and two silicon elliptical cylinders located on the amorphous silicon film;

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

[0102] The preparation module 40 is used to prepare the all-optical polarization switch using a micro-nano preparation process according to the polarization switch simulation model.

[0103] In a possible implementation, the model building module 20 builds an initial simulation model according to preset parameters, including:

[0104] Placing two silicon elliptical cylinders in each of the basic units on the corresponding amorphous silicon film in an upright state based on a preset geometric center distance, and the elliptical major axes of each silicon elliptical cylinder are parallel to each other;

[0105] Establishing an xyz three-dimensional rectangular coordinate system for each of the basic units, wherein the plane constructed by the x-axis and the y-axis is parallel to the plane where the amorphous silicon 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] Tilt the two silicon elliptical cylinders in each of the basic units in the x-axis direction at a preset tilt angle;

[0108] Setting periodic boundary conditions of each of the basic units in the x-direction and the y-direction;

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

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

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

[0112] Using preset polarized light to inject into the initial simulation model, and obtaining corresponding reflected light;

[0113] Calculating and obtaining the polarization spectrum of the reflected light;

[0114] Determining whether the initial simulation model meets the performance requirement according to the polarization spectrum;

[0115] If the performance requirement is not met, the inclination 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 requirement, thereby obtaining the polarization switch simulation model.

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

[0117] In one possible implementation, in the process of the preparation module 40 using a micro-nano preparation process to prepare the all-optical polarization switch, an inclined etching process is used to etch the silicon sample on the amorphous silicon film according to the inclination angle of each silicon elliptical cylinder in the polarization switch simulation model to obtain silicon elliptical cylinders with inclination angles.

[0118] The embodiment of the present application provides a system for preparing an all-optical polarization switch. By constructing a simulation model and using a simulation calculation method to determine the various parameters of the polarization switch simulation model, the embodiment of the present application can prepare a corresponding all-optical polarization switch based on the performance requirements of the polarization switch, thereby improving the efficiency and accuracy of the preparation of the all-optical polarization switch. In addition, the all-optical polarization switch prepared by the embodiment of the present application is an intrinsic chiral resonance silicon-based metasurface, which realizes the intrinsic chiral resonance through the arranged silicon elliptical cylinder structure on the amorphous silicon film, thereby improving the application range and response speed of the polarization switch. Specifically, in the process of using the all-optical polarization switch, the all-optical polarization switch can be excited by pump light, and the pump light will be incident on the silicon-based resonant cavity to excite the dynamics of carriers and cause the rapid change of the refractive index of amorphous silicon. When the refractive index of silicon changes, the chiral resonance will move, thereby achieving a rapid polarization response, and the all-optical polarization switch operates in the visible light band, thereby improving the band application range and response speed of the polarization switch.

[0119] The more detailed working principle and step flow of this embodiment can refer to, but are not limited to, the relevant records of Embodiment 1.

[0120] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the scope of protection of the present application. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing an all-optical polarization switch, characterized in that: include: Acquire performance requirements of the polarization switch, where the performance requirements are corresponding indicators of transmission, reflection or absorption of the polarization switch for each type of polarized light; Constructing an initial simulation model according to preset parameters, wherein the initial simulation model is an intrinsic chiral resonant silicon-based metasurface, which is composed of a plurality of basic units arranged, each of which includes an amorphous silicon film and two silicon elliptical cylinders located on the amorphous silicon film; According to the performance requirements, adjusting preset parameters of the initial simulation model by a finite element method until the initial simulation model meets the performance requirements, thereby obtaining a polarization switch simulation model; According to the polarization switch simulation model, the all-optical polarization switch is manufactured using a micro-nano manufacturing process.

2. The method for preparing an all-optical polarization switch according to claim 1, characterized in that: The initial simulation model is constructed according to preset parameters, including: Placing two silicon elliptical cylinders in each of the basic units on the corresponding amorphous silicon film in an upright state based on a preset geometric center distance, and the elliptical major axes of each silicon elliptical cylinder are parallel to each other; Establishing an xyz three-dimensional rectangular coordinate system for each of the basic units, wherein the plane constructed by the x-axis and the y-axis is parallel to the plane where the amorphous silicon film is located, and the y-axis is parallel to the major axis of the ellipse; 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; Tilt the two silicon elliptical cylinders in each of the basic units in the x-axis direction at a preset tilt angle; Setting periodic boundary conditions of each of the basic units in the x-direction and the y-direction; Disposing two matching layers in the z direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon film, and the other matching layer is located above the two silicon elliptical cylinders; The basic units are arranged along the x-axis direction to construct the initial simulation model.

3. The method for preparing an all-optical polarization switch according to claim 2, characterized in that: The step of adjusting preset parameters of the initial simulation model by a finite element method according to the performance requirement until the initial simulation model meets the performance requirement includes: Using preset polarized light to inject into the initial simulation model, and obtaining corresponding reflected light; Calculating and obtaining the polarization spectrum of the reflected light; Determining whether the initial simulation model meets the performance requirement according to the polarization spectrum; If the performance requirement is not met, the inclination 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 requirement, thereby obtaining the polarization switch simulation model.

4. The method for preparing an all-optical polarization switch according to claim 1, characterized in that: The preset parameters include the finite element method calculation period, the elliptical major axis and the elliptical minor axis of the silicon elliptical cylinder, the geometric center distance between two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle and the tilt angle of the silicon elliptical cylinder.

5. The method for preparing an all-optical polarization switch according to claim 1, characterized in that: In the process of preparing the all-optical polarization switch using the micro-nano preparation process, the silicon sample on the amorphous silicon film is etched using an inclined etching process according to the inclination angle of each silicon elliptical cylinder in the polarization switch simulation model to obtain each silicon elliptical cylinder with an inclination angle.

6. A system for preparing an all-optical polarization switch, characterized in that: 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, where the performance requirements are corresponding indicators of the transmission, reflection or absorption of each type of polarized light by the polarization switch; 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 a plurality of basic units arranged, each of which includes an amorphous silicon film and two silicon elliptical cylinders located on the amorphous silicon film; The simulation calculation module is used to adjust the preset parameters of the initial simulation model by the finite element method according to the performance requirements, until the initial simulation model meets the performance requirements, so as to obtain a polarization switch simulation model; The preparation module is used to prepare the all-optical polarization switch using a micro-nano preparation process according to the polarization switch simulation model.

7. A system for preparing an all-optical polarization switch according to claim 6, characterized in that: The model building module builds an initial simulation model according to preset parameters, including: Placing two silicon elliptical cylinders in each of the basic units on the corresponding amorphous silicon film in an upright state based on a preset geometric center distance, and the elliptical major axes of each silicon elliptical cylinder are parallel to each other; Establishing an xyz three-dimensional rectangular coordinate system for each of the basic units, wherein the plane constructed by the x-axis and the y-axis is parallel to the plane where the amorphous silicon film is located, and the y-axis is parallel to the major axis of the ellipse; 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; Tilt the two silicon elliptical cylinders in each of the basic units in the x-axis direction at a preset tilt angle; Setting periodic boundary conditions of each of the basic units in the x-direction and the y-direction; Disposing two matching layers in the z direction based on a preset refractive index, wherein one matching layer is located below the amorphous silicon film, and the other matching layer is located above the two silicon elliptical cylinders; The basic units are arranged along the x-axis direction to construct the initial simulation model.

8. A system for preparing an all-optical polarization switch according to claim 7, characterized in that: The simulation calculation module adjusts preset parameters of the initial simulation model by a finite element method according to the performance requirement until the initial simulation model meets the performance requirement, including: Using preset polarized light to inject into the initial simulation model, and obtaining corresponding reflected light; Calculating and obtaining the polarization spectrum of the reflected light; Determining whether the initial simulation model meets the performance requirement according to the polarization spectrum; If the performance requirement is not met, the inclination 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 requirement, thereby obtaining the polarization switch simulation model.

9. The system for preparing an all-optical polarization switch according to claim 6, characterized in that: The preset parameters include the finite element method calculation period, the elliptical major axis and the elliptical minor axis of the silicon elliptical cylinder, the geometric center distance between two silicon elliptical cylinders in the basic unit, the height of the silicon elliptical cylinder, the rotation angle and the tilt angle of the silicon elliptical cylinder.

10. The system for preparing an all-optical polarization switch according to claim 6, characterized in that: In the process of the preparation module using the micro-nano preparation process to prepare the all-optical polarization switch, the silicon sample on the amorphous silicon film is etched using an inclined etching process according to the inclination angle of each silicon elliptical cylinder in the polarization switch simulation model to obtain each silicon elliptical cylinder with an inclination angle.

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