Polymorphic beam controller and preparation method thereof

Abstract

The invention provides a polymorphic beam controller and a preparation method thereof. The preparation method comprises the following steps: constructing a modulation unit structure based on a phase change material; constructing a metasurface radius-phase distribution library based on the modulation unit structure; screening a metasurface from the metasurface radius-phase distribution library according to a preset incident angle and a preset deflection angle of the polymorphic beam controller; and manufacturing the polymorphic beam controller based on the screening result. According to the invention, the metasurface radius-phase distribution library is constructed, and the appropriate metasurface size is selected according to the required incident angle and deflection angle, so that the polymorphic beam controller under the specific incident angle and emergent angle is constructed.

Description

Technical Field

[0001] The present application relates to the field of beam control devices, and more particularly, to a multi-state beam controller and a method for manufacturing the same. Background Art

[0002] As a basic optical device, a beam controller can deflect incident light by a certain angle and is a core component in application fields such as lidar detection. With the development of optical technology, beam control devices play an important role in fields such as lidar, optical communication, and display technology. Traditional mechanical beam controllers have problems such as slow response speed and large volume. Optical devices based on metasurfaces have gradually become a research hotspot due to their advantages such as thinness, high integration, and fast response speed.

[0003] The content in the background art section is only the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0004] The present application provides a multi-state beam controller and a method for manufacturing the same to solve the problems of slow response speed and large volume of beam controllers in the prior art.

[0005] According to one aspect of the present application, a method for manufacturing a multi-state beam controller is provided, including:

[0006] Constructing a modulation unit structure based on a phase change material;

[0007] Based on the modulation unit structure, constructing a metasurface radius-phase distribution library;

[0008] According to the preset incident angle and preset deflection angle of the multi-state beam controller, screening a metasurface from the metasurface radius-phase distribution library; and

[0009] Manufacturing the multi-state beam controller based on the screening result.

[0010] In some embodiments of the present application, constructing a modulation unit structure based on a phase change material includes:

[0011] Determining a phase change material based on the multi-state beam controller; and

[0012] Constructing the modulation unit structure according to the phase change material.

[0013] In some embodiments of the present application, the modulation unit structure includes a column provided on the top of the modulation unit structure, and the column is a cylinder;

[0014] Based on the modulation unit structure, constructing a metasurface radius-phase distribution library includes:

[0015] Using the finite-difference time-domain method, by changing the radius, height, and period of the upright post, the phase and reflectivity are varied, and then the distribution points covering a predetermined phase range and having a predetermined reflectivity are selected as the super-surface radius-phase distribution in the super-surface radius-phase distribution library.

[0016] In some embodiments of the present application, screening the super-surface from the super-surface radius-phase distribution library according to the preset incident angle and the preset deflection angle of the multi-state beam controller includes:

[0017] Determining the phase increment of the required super-surface according to the preset incident angle and the preset deflection angle of the multi-state beam controller; and

[0018] Screening the super-surface from the super-surface radius-phase distribution library according to the phase increment.

[0019] In some embodiments of the present application, the phase increment of the required super-surface is determined by Equation (1):

[0020]

[0021] where θ r is the preset deflection angle, n r is the reflection coefficient of the deflection interface, θ i is the preset incident angle, n i is the reflection coefficient of the incident interface, λ0 is the wavelength of the incident light, Δφ is the phase increment introduced by each upright post, and d is the period of each upright post.

[0022] In some embodiments of the present application, fabricating the multi-state beam controller based on the screening result includes:

[0023] Fabricating the gate and the super-surface of the multi-state beam controller based on the screening result.

[0024] In some embodiments of the present application, the preparation method further includes:

[0025] Simulating the screening result and confirming whether the simulation result meets the requirements;

[0026] If not, modifying the modulation unit structure.

[0027] In some embodiments of the present application, simulating the screening result includes:

[0028] Calculating the effective dielectric constant of the phase change material at different crystallization ratios; and

[0029] Simulating the optical performance of the multi-state beam controller based on the effective dielectric constant.

[0030] In some embodiments of the present application, the effective dielectric constant is calculated by formula (2):

[0031]

[0032] where ε eff is the effective dielectric constant, ε a and ε c are the dielectric constants of the phase change material in the amorphous state and the crystalline state respectively, m is the crystallization ratio, and the value range of m is 0 to 1.

[0033] On the other hand, the present application provides a multi-state beam controller prepared by the preparation method described in any one of the above.

[0034] The present application constructs a hypersurface radius-phase distribution library, selects appropriate hypersurface sizes according to the required incident angle and deflection angle, and thus constructs a multi-state beam controller under specific incident angles and exit angles.

[0035] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. By referring to the drawings and describing its exemplary embodiments in detail, the above and other objectives, features and advantages of the present application will become more obvious.

[0037] Figure 1 It is a flowchart of the preparation of the multi-state beam controller provided by an embodiment of the present application.

[0038] Figure 2 It is a schematic diagram of the modulation unit structure constructed by an embodiment of the present application. <*

[0039] Figure 3 It is a gradient diagram of the phase and reflectivity of the modulation unit structure provided by an embodiment of the present application changing with the radius distribution.

[0040] Figure 4 It is a schematic diagram of the hypersurface structure of the multi-state beam controller provided by an embodiment of the present application.

[0041] Figure 5 It is a schematic diagram of the structure of the multi-state beam controller provided by an embodiment of the present application.

[0042] Figures 6(a) to 6(h)Optical field modulation diagrams of the polymorphic beam controller provided by an embodiment of the present application in different crystallization states. Among them, the phase change material Ge2Sb2Te5 (GST225) is in the amorphous state in Fig. 6(a), the crystallization ratio of GST225 is 10% in Fig. 6(b), the crystallization ratio of GST225 is 20% in Fig. 6(c), the crystallization ratio of GST225 is 30% in Fig. 6(d), the crystallization ratio of GST225 is 40% in Fig. 6(e), the crystallization ratio of GST225 is 60% in Fig. 6(f), the crystallization ratio of GST225 is 80% in Fig. 6(g), and the crystallization ratio of GST225 is 100% in Fig. 6(h). Detailed implementation manners

[0043] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar parts, and thus their repeated description will be omitted.

[0044] The features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of these specific details, or other means, components, materials, devices, or operations, etc. may be adopted. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0045] The flowcharts shown in the accompanying drawings are merely illustrative and not necessarily include all the contents and operations / steps, nor are they necessarily executed in the order described. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to the actual situation.

[0046] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0047] The following will, with reference to the accompanying drawings, elaborate on the specific embodiments according to the present application.

[0048] A metasurface is a two-dimensional planar structure composed of sub-wavelength structural units, which can precisely control the phase, amplitude, polarization, etc. of light waves. By designing the structural units of the metasurface, functions such as beam deflection, focusing, and beam splitting can be achieved. The optical performance of the metasurface is mainly determined by the geometric shape and size of the structural units, as well as the dielectric constant of the material. After the device is fabricated, it is difficult to change the geometric shape and size of the structure, and the optical performance of the device needs to be adjusted or reconstructed by changing the dielectric constant of the material.

[0049] Photonic devices based on phase change material metasurfaces allow for multiple different optical field modulations to be achieved on the same metasurface, which benefits from the multi-level phase change ability of phase change materials. Phase change materials are a class of materials that can reversibly transform between a crystalline state and an amorphous state under external stimuli. During the phase change process, significant changes occur in its optical properties such as refractive index and absorption rate, thus providing the possibility for dynamic regulation of optical devices.

[0050] This application proposes a multi-state beam control device based on a phase change material metasurface, which can achieve different angular deflections of the incident light field by changing the different crystallization ratios of the phase change material. The multi-state beam controller provided in this application combines a phase change material and a metasurface micro-nano structure to achieve dynamic regulation of the beam direction. When the phase change material transforms between the amorphous state and the crystalline state, a significant change occurs in the refractive index, enabling the metasurface to have multi-state programmable capabilities. By precisely designing the metasurface structure and using light, heat, or electrical triggers for phase change, it is possible to switch between multiple beam control modes, which are widely used in fields such as adaptive optics, lidar, optical communication, and dynamic holographic display.

[0051] Figure 1 The preparation method of the multi-state beam controller provided in an embodiment of this application is shown, as Figure 1 shown, the preparation method includes steps S1 to S4. Hereinafter, taking Figure 1 as an example, the preparation method of a multi-state beam controller based on a phase change material metasurface according to an exemplary embodiment of this application will be described in detail.

[0052] As Figure 1 shown, in step S1, a modulation unit structure based on a phase change material is constructed.

[0053] The phase change material includes chalcogenide compounds, for example, Ge2Sb2Te5 (abbreviated as GST225 in this application), Sb2Te3, etc. According to the embodiment of this application, the multi-state beam controller based on a phase change material metasurface is a multi-state beam controller including a metasurface of a phase change material.

[0054] According to the embodiment of this application, the modulation unit structure based on a phase change material metasurface can be constructed through the following steps:

[0055] Determine a phase change material based on a polymorphic beam controller; and

[0056] Construct a modulation unit structure according to the phase change material.

[0057] In this application, the modulation unit structure can be determined according to the performance requirements of the polymorphic beam controller and the specific type of the phase change material.

[0058] Taking a reflective beam controller as an example, first determine the phase change material Ge2Sb2Te5 (GST225), and then construct a modulation unit structure based on GST225. Figure 2 FIG. shows a schematic diagram of a modulation unit structure of a reflective beam controller based on GST225 provided by an embodiment of this application. As Figure 2 shown, the modulation unit structure is a metal-dielectric-metal structure, and uses plasmon enhancement to achieve the modulation function. The modulation unit structure from bottom to top is a silicon dioxide (SiO2) substrate, a gold (Au) layer, a first aluminum oxide (Al2O3) layer, a GST225 layer, a second Al2O3 layer, and Au posts. Among them, the functions of the first Al2O3 layer and the second Al2O3 layer are to prevent the GST225 layer from oxidizing.

[0059] Optionally, the thickness of the SiO2 substrate is 400-600 μm. Optionally, the thickness of the Au layer can be 50-150 nm. Optionally, the thickness of the first Al2O3 layer can be 15-25 nm. Optionally, the thickness of the GST225 layer can be 40-60 nm. Optionally, the thickness of the second Al2O3 layer can be 15-25 nm. Figure 2 In the shown embodiment, the thickness of the SiO2 substrate is 500 μm, the thickness of the Au layer is 100 nm, the thickness of the first Al2O3 layer is 20 nm, the thickness of the GST225 layer is 50 nm, and the thickness of the second Al2O3 layer is 20 nm.

[0060] In step S2, based on the modulation unit structure, construct a metasurface radius-phase distribution library.

[0061] The post is located at the top of the modulation unit structure and is in a cylindrical shape, such as Figure 2 the shown Au post.

[0062] According to an embodiment of this application, the finite-difference time-domain method (FDTD) can be used. By changing the radius, height, and period of the post, the phase and reflectivity changes can be achieved, and then the distribution points covering a predetermined phase range and having a predetermined reflectivity are selected as the metasurface radius-phase distribution in the metasurface radius-phase distribution library. Generally speaking, the distribution points covering a larger phase range and having a high reflectivity can be selected as the metasurface radius-phase distribution in the metasurface radius-phase distribution library.

[0063] Taking Figure 2 the modulation unit structure shown as an example, its column is an Au column. The FDTD method can be used to obtain the gradient of the phase and reflectivity of the Au column changing with the radius distribution. Figure 3 It shows the gradient of the phase and reflectivity of the Au column changing with the radius distribution when the period P of the Au column is 700 nm, the height H is 110 nm, and the radius change range is 50 - 300 nm. From Figure 3 it can be seen that when the period of the Au column is 700 nm, the height is 110 nm, and the radius change range is 50 - 300 nm, it can cover a 270° phase distribution, and at the same time, the reflectivity at most radius distribution points is above 70%. Taking this as Figure 2 the metasurface radius - phase distribution library of the modulation unit structure shown, the gradient change of the reflected light phase can be realized through this distribution, so as to realize different - angle deflections of the vertically incident light by regulating the phase gradient.

[0064] In step S3, according to the preset incident angle and preset deflection angle of the multi - state beam controller, the metasurface is screened from the metasurface radius - phase distribution library.

[0065] For a reflective beam controller, the refraction and reflection of light at the metasurface satisfy the generalized Snell's law, that is: at the interface of two materials with different refractive indices, the deflection angle of the outgoing light is not only affected by the refractive index of the material and the incident angle, but also related to the phase jump gradient introduced by the metasurface.

[0066] According to the embodiments of the present application, the metasurface can be screened through the following steps:

[0067] According to the preset incident angle and preset deflection angle of the multi - state beam controller, determine the phase increment of the required metasurface; and

[0068] Screen the metasurface from the metasurface radius - phase distribution library according to the phase increment.

[0069] To achieve beam deflection at a given angle, a specific phase jump gradient can be introduced as needed, and the phase increment of the required metasurface is determined by formula (1):

[0070]

[0071] where θ r is the preset deflection angle, n r is the reflection coefficient of the deflection interface, θ i is the preset incident angle, n iis the reflection coefficient of the incident interface. Here, for the reflective beam controller, both the deflection interface and the incident interface are air, and the refractive index of air is 1. λ0 is the wavelength of the incident light, Δφ is the phase increment introduced by each pillar, and d is the period of each pillar. Different angle deflections can be achieved by changing d or Δφ. Then, according to the phase increment, a suitable metasurface is selected from the aforementioned metasurface radius-phase distribution library.

[0072] For Figure 2 the modulation unit structure shown, d in the above formula (1) is 700 nm. Considering the light is vertically incident, the preset incident angle θ i is 0°, the preset deflection angle θ r is 20°, n r and n i are both the air refractive index 1, and λ0 is the incident light wavelength 1550 nm. The phase increment Δφ can be calculated. For Figure 2 the modulation unit structure shown, 5 Au pillars can be selected through the phase increment Δφ. The metasurface structure composed of them is as Figure 4 shown, from bottom to top are a 500-μm SiO2 substrate, a 100-nm Au layer, a 20-nm first Al2O3 layer, a 50-nm GST225 layer, a 20-nm second Al2O3 layer, and 5 Au pillars with different radii, each with a period of 700 nm and a height of 110 nm.

[0073] In step S4, a multi-state beam controller is fabricated based on the screening result.

[0074] After determining the metasurface, a multi-state beam controller can be fabricated.

[0075] According to the embodiments of the present application, a multi-state beam controller can be fabricated through the following steps:

[0076] Fabricate the gate and metasurface of the multi-state beam controller based on the screening result.

[0077] For Figure 4 the metasurface unit structure shown, a gold thin film can be deposited on the substrate by physical vapor deposition to fabricate the gate and electrodes; then, alumina and phase change materials are respectively deposited on the gold thin film by magnetron sputtering; then, a gold thin film is deposited on the alumina by physical vapor deposition, and electron beam lithography is used for metasurface pattern transfer and etching. After removing the template, a multi-state beam controller device based on the phase change material metasurface is obtained.

[0078] Specifically, first, a 100-nm-thick Au film can be deposited on a 500-μm-thick SiO2 substrate by physical vapor deposition to fabricate the gate and electrodes. Then, 20-nm-thick Al2O3, 50-nm-thick GST225, and 20-nm-thick Al2O3 are respectively deposited on the Au film by magnetron sputtering. Next, a 110-nm-thick Au film is deposited on the Al2O3 by physical vapor deposition, and the metasurface pattern is transferred and etched by electron beam lithography. After removing the template, a multi-state beam control device based on the phase change material metasurface is obtained, such as Figure 5 as shown

[0079] Figure 5 The multi-state beam controller based on GST225 as shown can control the multi-angle deflection of the reflected light from about 20° to 0° by adjusting the crystallization degree of GST225, realizing multi-state reconfigurability.

[0080] In some embodiments of the present application, the above preparation method may further include between steps S3 and S4: simulating the screening results and confirming whether the simulation results meet the requirements;

[0081] If not, modify the modulation unit structure.

[0082] That is, if the simulation structure does not meet the requirements, correct from step S1. If the simulation results meet the requirements, step S4 can be carried out.

[0083] According to the embodiments of the present application, the screening results can be simulated through the following steps:

[0084] Calculating the effective dielectric constant of the phase change material at different crystallization ratios; and

[0085] Simulating the optical performance of the multi-state beam controller based on the effective dielectric constant.

[0086] Among them, in a specific embodiment, the effective dielectric constant can be calculated by formula (2):

[0087]

[0088] Among them, ε eff is the effective dielectric constant, ε a and ε c are the dielectric constants of the phase change material in the amorphous state and the crystalline state respectively, and m is the crystallization ratio, and its variation range is 0 to 1.

[0089] By regulating the crystallization ratio m, the effective dielectric constant ∈ a of the phase change material can be adjusted within the range of [∈ c , ∈ eff, realizing continuous regulation of the optical performance of the device. Based on FDTD simulation, the performance of this device structure at a wavelength of 1550 nm was evaluated, and the results are shown in Figure 6. The crystallization ratio of GST225 was gradually increased from 0% to 100%, and the change of the reflected light field was observed. From Figures 6(a) to 6(h) It can be seen that when GST225 is in the amorphous state (A_GST), the light passing through this gradient metasurface structure causes the reflected light to tilt, showing that the deflection angle of the reflected light is about 22°, which is close to the designed 20°. As the crystallization ratio continues to increase, the reflected light field changes from deflection to no deflection. In the case of a relatively low crystallization ratio, the deflection angle gradually decreases. When the crystallization ratio reaches 100% (C_GST), the reflected light field basically has no deflection, and the deflection angle is 0° at this time. This result indicates that by controlling the crystallization ratio of GST225, optical field modulation of at least 6 states can be achieved.

[0090] In this application, a metasurface radius-phase distribution library is constructed, and appropriate metasurface sizes are selected according to the required incident angle and deflection angle, so as to construct a multi-state beam controller under specific incident angles and exit angles.

[0091] The embodiments of the present application have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. At the same time, any changes or deformations made by those skilled in the art based on the idea of the present application, within the specific implementation manner and application scope of the present application, all belong to the protection scope of the present application. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A preparation method of a polymorphic beam controller, characterized in that, Comprising: Constructing a modulation unit structure based on a phase change material; Based on the modulation unit structure, constructing a metasurface radius-phase distribution library; According to the preset incident angle and preset deflection angle of the multi-state beam controller, screening metasurfaces from the metasurface radius-phase distribution library; And Fabricating the multi-state beam controller based on the screening result.

2. The preparation method according to claim 1, characterized in that, Constructing a modulation unit structure based on a phase change material includes: Determining the phase change material based on the multi-state beam controller; and Constructing the modulation unit structure according to the phase change material.

3. The preparation method according to claim 1, wherein, The modulation unit structure includes a column provided at the top of the modulation unit structure, and the column is a cylinder; Based on the modulation unit structure, constructing a metasurface radius-phase distribution library includes: Using the finite-difference time-domain method, by changing the radius, height, and period of the column, realizing phase and reflectivity changes, and then selecting distribution points covering a predetermined phase range and having a predetermined reflectivity as the metasurface radius-phase distribution in the metasurface radius-phase distribution library.

4. The preparation method according to claim 3, characterized in that, According to the preset incident angle and preset deflection angle of the multi-state beam controller, screening metasurfaces from the metasurface radius-phase distribution library includes: Determining the phase increment of the required metasurface according to the preset incident angle and the preset deflection angle of the multi-state beam controller; and Screening metasurfaces from the metasurface radius-phase distribution library according to the phase increment.

5. The preparation method according to claim 4, wherein The phase increment of the required metasurface is determined by formula (1): Among them, θ r is the preset deflection angle, n r is the reflection coefficient of the deflection interface, θ i is the preset incident angle, n i is the reflection coefficient of the incident interface, λ0 is the wavelength of the incident light, Δφ is the phase increment introduced by each column, and d is the period of each column.

6. The preparation method according to claim 1, wherein Fabricating the multi-state beam controller based on the screening result includes: Fabricating the gate and metasurface of the multi-state beam controller based on the screening result.

7. The preparation method according to claim 1, characterized in that, Further comprising: Simulating the screening result and confirming whether the simulation result meets the requirements; If not, modifying the modulation unit structure.

8. The preparation method according to claim 7, wherein, Simulating the screening result includes: Calculating the effective dielectric constant of the phase change material at different crystallization ratios; and Simulating the optical performance of the multi-state beam controller based on the effective dielectric constant.

9. The preparation method according to claim 8, characterized in that, The effective dielectric constant is calculated by formula (2): where ε eff is the effective dielectric constant, ε a and ε c are the dielectric constants of the phase change material in the amorphous state and the crystalline state, respectively, m is the crystallization ratio, and the value range of m is 0 to 1.

10. A polymorphic beam controller, characterized in that, Prepared by using the preparation method according to any one of claims 1 to 9.

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