An arbitrary active phase control electromagnetic metasurface and a preparation method thereof

Abstract

The application provides an arbitrary active phase control electromagnetic super surface, comprising a substrate, an active phase control layer and a passive phase control layer sequentially arranged on the substrate, a microstructure unit of the active phase control layer is a circular opening resonant ring structure composed of an active control material, a microstructure unit of the passive phase control layer is a circular opening resonant ring structure composed of a good conductor material and having the same center as the microstructure unit of the active phase control layer, an outer diameter of a resonant ring of the passive phase control layer is different from that of the active phase control layer, an inner diameter of the resonant ring of the passive phase control layer is different from that of the active phase control layer, and a resonant ring opening area of the passive phase control layer has no overlapping part with that of the active phase control layer. The arbitrary active phase control super surface provided by the application can realize an additional phase of any requirement through the control of geometric corners of the opening resonant rings of the passive phase control layer and the active phase control layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phase control metasurface, more particularly, to an arbitrary active phase control electromagnetic metasurface and a preparation method thereof. BACKGROUND

[0002] The phase control metasurface is a device that can control the phase of electromagnetic waves. The phase control device realized by the metasurface can break through the limitation of the thickness of electromagnetic wavelength, and has very rich functions and can be designed artificially, which has surpassed the traditional phase control device in many aspects; and is widely used in planar superlenses, vortex light generation, photonic spin Hall effect excitation and many other fields.

[0003] In order to realize the metasurface that can control the phase, researchers found that the geometric corner of the microstructure unit of the metasurface is directly related to the additional phase of the incident electromagnetic wave of a certain polarization state, in addition, the electromagnetic wave mode propagation of the microstructure with a certain thickness of different media can also realize the phase control of the electromagnetic wave.

[0004] However, the current phase control metasurface is mainly passive control, and since the geometric structure design is limited by the required phase, it is difficult to realize arbitrary active phase control on the basis of passive phase control, which limits the development of the phase control metasurface. SUMMARY

[0005] Therefore, the purpose of the present application is to provide an arbitrary active phase control electromagnetic metasurface and a preparation method thereof, so as to solve the problem that the current phase control metasurface is difficult to realize active control.

[0006] The present application provides an arbitrary active phase control electromagnetic metasurface, comprising:

[0007] a substrate;

[0008] an active phase control layer and a passive phase control layer successively located on the substrate;

[0009] the microstructure unit of the active phase control layer is a circular opening resonant ring structure composed of an active control material;

[0010] the microstructure unit of the passive phase control layer is a circular opening resonant ring structure composed of a good conductor material and having the same center as the microstructure unit of the active phase control layer;

[0011] the outer diameter of the resonant ring of the passive phase control layer is different from that of the active phase control layer, the inner diameter of the resonant ring of the passive phase control layer is different from that of the active phase control layer, and the resonant ring opening area of the passive phase control layer has no overlapping part with the resonant ring opening area of the active phase control layer.

[0012] Preferably, the substrate is a specified crystal plane thickness of substrate material that achieves lattice matching with the active control material.

[0013] Preferably, the active control material is selected from one or more of silicon, graphene, vanadium dioxide and GST.

[0014] Preferably, the good conductor material is selected from one or more of gold, silver, platinum, aluminum and copper.

[0015] Preferably, the active phase control layer and the passive phase control layer are both two-dimensional periodic square arrays.

[0016] Preferably, the two-dimensional array period of the two-dimensional periodic square array is 100 nm to 10 mm.

[0017] Preferably, the outer diameter of the resonant ring of the passive phase control layer is smaller than the outer diameter of the resonant ring of the active phase control layer, and the inner diameter of the resonant ring of the passive phase control layer is larger than the inner diameter of the resonant ring of the active phase control layer.

[0018] Preferably, the circular opening resonant ring structure of the active phase control layer and the circular opening resonant ring structure of the passive phase control layer can be rotated at any angle around the center of the circle.

[0019] The present application also provides a preparation method of any of the active phase control electromagnetic super surfaces described in the above technical solutions, characterized in that it comprises the following steps:

[0020] a) growing the active control material on the substrate, and forming the active phase control layer through first etching;

[0021] b) growing the good conductor material on the substrate with the active phase control layer, and making the thickness of the formed good conductor material layer exceed that of the active phase control layer, forming the passive phase control layer through second etching, and obtaining the active phase control electromagnetic super surface.

[0022] The application provides an arbitrary active phase control electromagnetic super surface, comprising a substrate, an active phase control layer and a passive phase control layer arranged on the substrate in sequence, a microstructure unit of the active phase control layer is a circular opening resonant ring structure composed of an active control material, a microstructure unit of the passive phase control layer is a circular opening resonant ring structure composed of a good conductor material and having the same center as the microstructure unit of the active phase control layer, an outer diameter of the resonant ring of the passive phase control layer is different from that of the active phase control layer, an inner diameter of the resonant ring of the passive phase control layer is different from that of the active phase control layer, and the resonant ring opening area of the passive phase control layer has no overlapping part with the resonant ring opening area of the active phase control layer.

[0023] In addition, the preparation method provided by the application has simple process, mild and controllable conditions, and wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A phase control super surface structure unit schematic diagram provided by the embodiment of the application is shown in the figure.

[0025] Figure 2 A phase control super surface structure unit top view provided by the embodiment of the application is shown in the figure.

[0026] Figures 3-6 A phase control super surface finite element simulation result schematic diagram provided by the embodiment of the application is shown in the figure.

[0027] Figure 7 A flow chart of the preparation method of the phase control super surface provided by the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0028] The technical solutions of the application will be described clearly and completely in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0029] The application provides an arbitrary active phase control electromagnetic super surface, comprising:

[0030] a substrate,

[0031] The active phase control layer and the passive phase control layer are sequentially located on the substrate;

[0032] The microstructure unit of the active phase control layer is a circular opening resonant ring structure composed of an active control material;

[0033] The microstructure unit of the passive phase control layer is a circular opening resonant ring structure composed of a good conductor material and having the same center as the microstructure unit of the active phase control layer;

[0034] The resonant ring outer diameter of the passive phase control layer is different from the resonant ring outer diameter of the active phase control layer, the resonant ring inner diameter of the passive phase control layer is different from the resonant ring inner diameter of the active phase control layer, and the resonant ring opening area of the passive phase control layer has no overlapping part with the resonant ring opening area of the active phase control layer.

[0035] Any active phase control electromagnetic metasurface provided by the application is applied to the technical fields of microwave communication, planar superlens, vortex light generation, photonic spin Hall effect excitation and the like.

[0036] Referring to Figure 1 Any active phase control electromagnetic metasurface provided by the application includes a substrate 10 and an active phase control layer 11 and a passive phase control layer 12 sequentially located on the substrate 10.

[0037] In the application, the microstructure unit (hereinafter referred to as active layer structure) of the active phase control layer 11 is a circular opening resonant ring structure composed of an active control material; the microstructure unit (hereinafter referred to as passive layer structure) of the passive phase control layer 12 is a circular opening resonant ring structure composed of a good conductor material and having the same center as the microstructure unit of the active phase control layer.

[0038] In the present application, the substrate is preferably a substrate material of a specified crystal face thickness that is lattice-matched with the active regulation material; the active regulation material is preferably selected from one or more of silicon, graphene, vanadium dioxide, and GST, and more preferably is silicon, graphene, vanadium dioxide, or GST; and the good conductor material is preferably selected from one or more of gold, silver, platinum, aluminum, and copper, and more preferably is gold, silver, platinum, aluminum, or copper. In the most preferred embodiment of the present application, the substrate is R-surface sapphire (<1012> crystal face aluminum oxide), the active regulation material is single-crystal silicon, and the good conductor material is gold; in other embodiments of the present application, the substrate is aluminum oxide, the active regulation material is vanadium dioxide, and the good conductor material is aluminum or gold; or, the substrate is silicon dioxide, the active regulation material is GST, and the good conductor material is gold or platinum; or, the substrate is polyimide resin, the active regulation material is single-layer graphene, and the good conductor material is gold. The present application has found, based on a large number of experiments, that under fixed geometric structure parameters, the above-mentioned changes in materials have little effect on the data of multiple embodiments.

[0039] In the present application, the passive layer structure has an outer diameter that is different from the outer diameter of the active layer structure, and preferably the outer diameter of the passive layer structure is smaller than the outer diameter of the active layer structure; the passive layer structure has an inner diameter that is different from the inner diameter of the active layer structure, and preferably the inner diameter of the passive layer structure is larger than the inner diameter of the active layer structure; and the active layer structure and the passive layer structure do not have overlapping regions in the opening area of the resonant ring (hereinafter referred to as the restriction condition).

[0040] In the present application, the active phase control layer 11 and the passive phase control layer 12 are both two-dimensional periodic square arrays of microstructure units; the two-dimensional array period of the two-dimensional periodic square array is preferably 100 nm to 10 mm.

[0041] In the present application, the circular opening resonant ring structure of the active phase control layer 11 and the circular opening resonant ring structure of the passive phase control layer 12 can both be rotated by any angle around the center of the circle under the aforementioned restriction condition; and the additional phase of the entire microstructure before and after active regulation is achieved by the respective angles of rotation.

[0042] In the present application, the active phase control layer 11 and the passive phase control layer 12 provide additional phase before and after active regulation of the metasurface, respectively. According to the geometric phase principle, for any two-dimensional metasurface of a square array of microstructures, without considering nonlinear effects, the additional phase (hereinafter referred to as the additional phase) generated by the conversion of the left-handed circularly polarized component in the incident electromagnetic wave to the right-handed circularly polarized component in the outgoing electromagnetic wave and the conversion of the right-handed circularly polarized component in the incident electromagnetic wave to the left-handed circularly polarized component in the outgoing electromagnetic wave (hereinafter collectively referred to as cross-polarization scattering) has a two-fold relationship with the geometric rotation angle of the microstructure, and the signs of the additional phases of the two cross-polarization scattering components are opposite.

[0043] For the super surface provided by the application, before active regulation, the active regulation material in the active phase regulation layer 11 is in a dielectric state and does not resonate with the incident electromagnetic wave; at this time, the electromagnetic characteristics of the super surface as a whole are directly related to the geometric structure of the passive phase regulation layer 12, and by adjusting any geometric corner of the passive layer structure, the additional phase of the super surface as a whole before active regulation can be achieved. After active regulation, the active regulation material in the active phase regulation layer 11 is in an electric conductor state, and under the foregoing restriction condition, the electromagnetic characteristics of the super surface as a whole are directly related to the overall closed asymmetric circular ring geometric structure formed by the active layer structure and the passive layer structure; since the closed asymmetric circular ring maintains the four-axis asymmetry of the microstructure along the normal direction of the super surface, the electromagnetic characteristics of the super surface still maintain a certain cross-polarization scattering intensity, and the additional phase of the closed asymmetric circular ring is only directly related to the geometric corner of the active layer structure; by adjusting any geometric corner of the active layer structure under the foregoing restriction condition, the additional phase of the super surface as a whole after active regulation can be achieved. As can be seen, the active phase regulation super surface provided by the application is orthogonal to the additional phase regulation effect before and after active regulation.

[0044] Since the phase regulation super surface is sensitive to geometric parameters, the structure parameters of the phase regulation super surface can be adjusted by calculation, such as adjusting the inner diameter, outer diameter, opening angle of the circular opening resonant ring of the active layer structure and the passive layer structure, and the array period of the super surface structure unit, so that the electromagnetic regulation effect of the phase regulation super surface can be optimized.

[0045] The active phase regulation super surface provided by the application adopts a specific structure and connection relationship, and can achieve any additional phase of a specified polarization state of an electromagnetic wave before and after active regulation; the additional phase before active regulation is controlled by the geometric corner of the opening resonant ring of the passive phase regulation layer, and the additional phase after active regulation is controlled by the geometric corner of the opening resonant ring of the active phase regulation layer, the regulation effects of which are orthogonal to each other, and under the foregoing constraint condition, the structure geometric corner can achieve any required additional phase.

[0046] The application further provides a preparation method of the active phase regulation electromagnetic super surface.

[0047] a) growing an active regulation material on a substrate, and forming an active phase regulation layer through first etching;

[0048] b) growing a good conductor material on the substrate with the active phase regulation layer, and making the thickness of the formed good conductor material layer exceed that of the active phase regulation layer, and forming a passive phase regulation layer through second etching, to obtain the active phase regulation electromagnetic super surface.

[0049] The application first grows an active phase control layer on the substrate after providing the substrate, and forms the active phase control layer through first etching.

[0050] In the application, the first etching is performed on the active phase control layer according to the expected phase requirement after active control, and the active phase control layer is etched according to the specified circular opening resonant ring structure to form the active phase control layer; and the active phase control layer is a two-dimensional square periodic array of the circular opening resonant ring.

[0051] Then, the application grows a good conductor material on the substrate with the active phase control layer, and makes the thickness of the formed good conductor material layer exceed that of the active phase control layer, and forms a passive phase control layer through second etching, thereby obtaining an arbitrary active phase control electromagnetic super surface.

[0052] The application grows a good conductor material on the active phase control layer of the super surface prepared in the application according to the expected phase requirement before active control, and forms a concentric circular opening resonant ring with a thickness exceeding that of the active phase control layer through photolithography and film plating, wherein the outer diameter of the resonant ring is smaller than that of the active phase control layer, and the inner diameter of the resonant ring is larger than that of the active phase control layer; and the passive phase control layer is a two-dimensional square periodic array of the circular opening resonant ring.

[0053] The preparation method provided by the application has simple process, mild and controllable conditions, and wide application prospect.

[0054] The application provides an arbitrary active phase control electromagnetic super surface, which comprises a substrate, an active phase control layer and a passive phase control layer sequentially arranged on the substrate, a microstructure unit of the active phase control layer is a circular opening resonant ring structure composed of an active control material, a microstructure unit of the passive phase control layer is a circular opening resonant ring structure composed of a good conductor material and having the same center as the microstructure unit of the active phase control layer, an outer diameter of a resonant ring of the passive phase control layer is different from that of the active phase control layer, an inner diameter of the resonant ring of the passive phase control layer is different from that of the active phase control layer, and there is no overlapping part between an opening area of the resonant ring of the passive phase control layer and an opening area of the resonant ring of the active phase control layer. Compared with the prior art, the arbitrary active phase control super surface provided by the application can realize arbitrary additional phase of a specified polarization state of an electromagnetic wave before and after active control by using a specific structure and connection relationship; the additional phase before active control is controlled by a geometric corner of an opening resonant ring of the passive phase control layer, the additional phase after active control is controlled by a geometric corner of an opening resonant ring of the active phase control layer, the control effects of the two are orthogonal to each other, and the structure geometric corner can realize an additional phase of arbitrary requirement under the foregoing constraint condition.

[0055] In addition, the preparation method provided by this invention is simple, mild and easy to control, and has broad application prospects.

[0056] To further illustrate the present invention, the following embodiments will be described in detail.

[0057] Example

[0058] See Figure 1 As shown, the arbitrary active phase-controlled electromagnetic metasurface provided by the present invention includes a substrate 10, and an active phase-controlled layer 11 and a passive phase-controlled layer 12 sequentially located on the substrate 10.

[0059] like Figure 2 As shown, to ensure the feasibility of the processing technology and the effect of arbitrary active phase electromagnetic control, the following conditions should be met: the outer diameter of the active layer structure r1 > p / 4; r1 > r2; the inner diameters of the active and passive layer structures r1-w1 < r2-w2; the opening angles of the active and passive layer structures satisfy 0° < α1 < 180°, 0° < α2 < 180°, α1 + α2 < 180°. The thickness of the passive layer exceeds the thickness of the active layer, and the total thickness of the active and passive layer structures does not exceed 1 / 5 of the wavelength of the controlled electromagnetic wave. In the optimal embodiment, r1 = 21 μm, w1 = 11 μm, α1 = 90°, r2 = 17 μm, w2 = 3 μm, α2 = 90°, p = 56 μm. Taking counterclockwise as the positive direction, the angles between the starting points of the open resonant rings of the active and passive layer structures and the x-axis are θ1 and θ2, respectively; the thickness of the active phase control layer is 0.6 μm, and the thickness of the passive phase control layer is 1 μm.

[0060] Furthermore, the preferred embodiment is a 10-layer material of R-face sapphire ( <1012> The material consists of 11 layers of monocrystalline silicon and 12 layers of gold.

[0061] The incident electromagnetic wave frequency is 1.62 THz, the incident polarization state is right-handed circularly polarized light, and the substrate material is R-plane sapphire ( <1012> The active phase modulation layer material is single-crystal silicon (alumina with a refractive index of 3.07), the real part of the relative permittivity is 11.7, and the imaginary part of the relative permittivity varies with the conductivity. The passive phase modulation layer material is Au.

[0062] The electromagnetic finite element simulation results of this structure are as follows: Figures 3-6 As shown; where, Figure 3 The relationship between the electromagnetic wave transmission intensity, additional phase, and geometric rotation of the passive layer structure when the active phase modulation layer material exhibits a dielectric state; Figure 4When the active phase modulation layer material behaves as an electrical conductor, under the condition of fixed passive layer structure geometric rotation angle θ2=0, the relationship between the electromagnetic wave transmission intensity and additional phase of the metasurface and the geometric rotation angle of the active layer structure is as follows: According to the aforementioned constraints, in order to ensure that the opening regions of the active and passive layer structures do not overlap, it is necessary to satisfy θ1+π / 2<θ2<θ1+3π / 2, that is, the part of the rotation angle from 90° to 270° in the figure. It can be seen that the additional phase in this region can obtain any value between 0 and 2π. Figure 5 The relationship between the additional phase corresponding to the rotation angle of various active layer structures and the conductivity of the active layer material under the condition of fixed passive layer structure rotation angle; Figure 6 The relationship between the additional phase corresponding to the conductivity of different active layer materials and the geometric rotation angle of the active and passive layer structures.

[0063] Depend on Figures 3-6 It is known that the geometric parameters of the active and passive layers play a decisive role in the phase modulation effect of the metasurface. When the active layer material is in a low conductivity state, the additional phase is only related to the geometric rotation angle of the passive layer structure and can take any value. When the active layer material is in a high conductivity state, within the aforementioned restricted region, the additional phase is only related to the geometric rotation angle of the active layer structure and can take any value. This achieves the orthogonal modulation effect of the metasurface on arbitrary phases before and after active modulation.

[0064] The method for preparing arbitrary active phase-controlled electromagnetic metasurfaces provided in this invention embodiment, such as... Figure 7 As shown, it includes:

[0065] S101: Based on the active phase modulation layer material required in the embodiment, a substrate material with a specified crystal plane thickness of 100μm-1000μm is provided to achieve lattice matching with the material; for the above-mentioned preferred embodiment, the substrate material is 460μm thick. <1012> Crystalline aluminum oxide.

[0066] S102: Form an active control material layer on the substrate.

[0067] Specifically, when the 11-layer material is vanadium dioxide, GST, or monocrystalline silicon, an actively controlled material layer of 5nm to 10μm can be epitaxially grown using methods such as magnetron sputtering, vacuum deposition, sputtering, sublimation, or chemical vapor deposition, depending on the process requirements. When the 11-layer material is monolayer graphene, the monolayer graphene can be transferred to the 10-layer substrate using a method of chemical etching followed by physical transfer. For the above-mentioned optimal embodiment, the actively controlled material layer is a 600nm thick epitaxially grown monocrystalline silicon film.

[0068] S103: Partial etching is performed on the two-dimensional geometric pattern composed of the active phase control material to form an active phase control layer on the substrate. The active phase control layer is a two-dimensional square periodic array.

[0069] The partial etching of the two-dimensional geometric pattern comprises:

[0070] The photoresist is selected according to the material properties of the 11 layers, and a photoetching mask plate corresponding to the required geometric pattern is prepared according to the positive and negative photoresist properties of the photoresist.

[0071] The photoresist is spin-coated on the surface of the 11 layers, exposed by the ultraviolet photoetching machine, and after development, fixing and other treatments, a photoresist protective surface with a specific geometric structure is formed.

[0072] According to the physical and chemical properties of the 11 layers of material, plasma etching or reactive ion etching is carried out on the device surface with photoresist protection, the etching depth is 11 layers thick, and after etching out the 10 substrate layer, the photoresist is washed away.

[0073] S104: Forming a passive phase control layer on the surface of the active phase control layer, the passive phase control layer is a two-dimensional square same period array.

[0074] The forming of the passive phase control layer on the surface of the active phase control layer comprises:

[0075] The passive phase control layer is grown by a photoetching technology.

[0076] Specifically, after forming the active phase control layer, forming photoresist on the surface of the active phase control layer and exposing and developing, a mask is formed, and then a passive control material with a thickness greater than the active phase control layer is grown on the mask; after removing the mask, the passive phase control layer is formed.

[0077] In the embodiment of the application, the active phase control layer and the passive phase control layer respectively provide any additional phase before and after active control, and the control effects before and after active control are orthogonal to each other, and through a microstructure unit array with appropriate geometric parameters, an electromagnetic metasurface with multiple phase characteristics can be realized.

[0078] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An arbitrary active phase control electromagnetic metasurface, comprising: a substrate; an active phase control layer and a passive phase control layer successively on the substrate; a microstructure unit of the active phase control layer is a circular open resonant ring structure composed of an active control material; a microstructure unit of the passive phase control layer is a circular open resonant ring structure composed of a good conductor material, and the microstructure unit of the passive phase control layer has the same center as the microstructure unit of the active phase control layer; an outer diameter of the resonant ring of the passive phase control layer is different from an outer diameter of the resonant ring of the active phase control layer, an inner diameter of the resonant ring of the passive phase control layer is different from an inner diameter of the resonant ring of the active phase control layer, and there is no overlapping part between an opening area of the resonant ring of the passive phase control layer and an opening area of the resonant ring of the active phase control layer.

2. The arbitrarily active phase-control electromagnetic metasurface according to claim 1, characterized in that, The substrate is a substrate material with a specified crystal face thickness that realizes lattice matching with the active control material.

3. The arbitrarily active phase-control electromagnetic metasurface according to claim 1, wherein, The active control material is selected from one or more of silicon, graphene, vanadium dioxide, and GST.

4. The arbitrarily active phase-control electromagnetic metasurface according to claim 1, wherein, The good conductor material is selected from one or more of gold, silver, platinum, aluminum, and copper.

5. The arbitrarily active phase-control electromagnetic metasurface according to claim 1, wherein, Both the active phase control layer and the passive phase control layer are two-dimensional same-period square arrays.

6. The arbitrarily active phase-control electromagnetic metasurface according to claim 5, characterized in that, A two-dimensional array period of the two-dimensional same-period square array is 100 nm to 10 mm.

7. The active phase-control electromagnetic metasurface of any one of claim 1, wherein, The outer diameter of the resonant ring of the passive phase control layer is smaller than the outer diameter of the resonant ring of the active phase control layer, and the inner diameter of the resonant ring of the passive phase control layer is larger than the inner diameter of the resonant ring of the active phase control layer.

8. The active phase-control electromagnetic metasurface of any one of claim 1, wherein, Both the circular open resonant ring structure of the active phase control layer and the circular open resonant ring structure of the passive phase control layer can be rotated at an arbitrary angle around the center.

9. A method of fabricating any of the active phase-controlled electromagnetic metasurfaces of any of claims 1-8, wherein, The method comprises the following steps: a) growing the active control material on the substrate, and forming the active phase control layer through first etching; b) growing the good conductor material on the substrate with the active phase control layer, and making the thickness of the formed good conductor material layer exceed the active phase control layer, forming the passive phase control layer through second etching, and obtaining the arbitrary active phase control electromagnetic metasurface.

Images