A metasurface structure with adjustable amplitude and phase of light field

Abstract

The present invention discloses a metasurface structure capable of adjusting both the amplitude and phase of a light field, comprising a substrate layer (1), an amplitude adjustment layer (2) and a phase adjustment layer (3); the lower end surface and the upper end surface of the substrate layer (1) are respectively provided with the amplitude adjustment layer (2) and the phase adjustment layer (3); the amplitude adjustment layer (2) is composed of a plurality of elliptical or rectangular nanocolumns (21) of the same specification but with different placement angles; the phase adjustment layer (3) is composed of a plurality of elliptical or rectangular nanocolumns (31) of different specifications; the placement angle of the nanocolumns (21) of the amplitude adjustment layer (2) is determined according to the amplitude of the desired light field, and the size of the nanocolumns (31) of the phase adjustment layer (3) is determined according to the phase of the desired light field. The metasurface structure capable of adjusting both the amplitude and phase of a light field provided by the present invention can realize simultaneous modulation of the amplitude and phase, which is conducive to fine control of the light field.

Description

Technical Field

[0001] The present invention relates to the field of nano-optics, and in particular to a metasurface structure capable of adjusting both the amplitude and phase of a light field. Background Art

[0002] Dielectric metasurfaces are important components for light field control. Currently, many dielectric metasurfaces that control light fields mainly roughly control the light field through phase. However, for fine control of light beams, it is necessary not only to control its phase but also its amplitude. Therefore, the development of dielectric metasurfaces that can adjust both the amplitude and phase of the light field is of great significance for light field control. Summary of the invention

[0003] In view of the deficiencies of the prior art, the present invention aims to provide a metasurface structure with adjustable amplitude and phase of a light field, which can realize simultaneous modulation of the amplitude and phase of a light field.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A metasurface structure capable of adjusting both the amplitude and phase of a light field, comprising a substrate layer, an amplitude adjustment layer and a phase adjustment layer; the lower end surface and the upper end surface of the substrate layer are respectively provided with the amplitude adjustment layer and the phase adjustment layer; the amplitude adjustment layer is composed of an arrangement of a plurality of elliptical or rectangular nanocolumns of the same specification but different placement angles; the phase adjustment layer is composed of an arrangement of a plurality of elliptical or rectangular nanocolumns of different specifications; the placement angle of the nanocolumns of the amplitude adjustment layer is determined according to the amplitude of a desired light field, and the size of the nanocolumns of the phase adjustment layer is determined according to the phase of the desired light field.

[0006] Furthermore, the amplitude adjustment layer and the phase adjustment layer are both made of high refractive index and low loss materials.

[0007] The present invention also provides a method for using the above-mentioned metasurface structure capable of adjusting both the amplitude and phase of the light field, which is specifically:

[0008] Determine the amplitude distribution and phase response distribution requirements under the illumination of linearly polarized light with an operating wavelength of λ;

[0009] According to the amplitude distribution requirement, determining the placement angle of each nanocolumn of the amplitude adjustment layer to obtain the required amplitude distribution;

[0010] According to the phase response distribution requirements, the required phase response distribution is obtained by changing the size of the nanorods at the corresponding positions in the phase adjustment layer.

[0011] Furthermore, for the phase adjustment layer, a phase response database is established by scanning the structure of the nano-columns of the phase adjustment layer, and then the size of each nano-column is selected from the phase response database according to the required phase response distribution.

[0012] The beneficial effect of the present invention is that the metasurface structure with adjustable light field amplitude and phase provided by the present invention can realize simultaneous modulation of amplitude and phase, which is conducive to fine control of the light field. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is an overall schematic diagram of a supersurface structure in an embodiment of the present invention;

[0014] Figure 2 A schematic diagram of the simple connection between the upper nanocolumns, the substrate layer, and the lower nanocolumns in an embodiment of the present invention;

[0015] Figure 3 is a schematic cross-sectional view of a lower nanocolumn of a unit structure in an embodiment of the present invention;

[0016] Figure 4 is a schematic cross-sectional view of an upper nanocolumn of a unit structure in an embodiment of the present invention;

[0017] Figure 5 Schematic diagram of the relationship between the amplitude and phase response of the two orthogonal polarization components of the light field of the elliptical nanorod in the amplitude adjustment layer in an embodiment of the present invention as θ changes;

[0018] Figure 6 The elliptical nanorods in the phase adjustment layer in the embodiment of the present invention satisfy the phase response covering the range of 0 to 2π under high transmission. Schematic diagram of the corresponding major and minor axis distribution;

[0019] Figure 7 Schematic diagram of the comparison results between the metasurface structure in which both the light field amplitude and phase are adjustable in this embodiment and the conventional method in which only phase regulation is performed. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0021] This embodiment provides a metasurface structure that can adjust both the amplitude and phase of the light field. Figure 1-4 As shown, it includes a substrate layer 1, an amplitude adjustment layer 2 and a phase adjustment layer 3. The lower end surface and the upper end surface of the substrate layer 1 are respectively provided with an amplitude adjustment layer 2 and a phase adjustment layer 3. The amplitude adjustment layer 2 is composed of a plurality of elliptical nanocolumns 21 of the same specifications but with different placement angles; the phase adjustment layer 3 is composed of a plurality of elliptical nanocolumns 31 of different specifications.

[0022] Furthermore, the substrate layer 1 is made of fused quartz material.

[0023] Furthermore, the lower layer elliptical nano-columns 21 and the upper layer elliptical nano-columns 31 are both made of silicon material.

[0024] In this embodiment, if Figure 2 As shown, the specifications of the lower elliptical nanocolumn 21 are: the major axis is D x1 , the minor axis is D y1 , the height is h1, the angle between its major axis and the x-axis is θ, and the length and width of the unit cell are S x1 , S y1 The specifications of the upper elliptical nanocolumn 31 are: the major axis is D x2 , the minor axis is D y2 , the height is h2, the length and width of the unit cell are S x2 , S y2 .

[0025] The metasurface structure in this embodiment, which is adjustable in both the amplitude and phase of the light field, determines the placement angles of each elliptical nanocolumn in the amplitude adjustment layer according to the required amplitude distribution, and determines the major axis and minor axis of each elliptical nanocolumn in the phase adjustment layer according to the required phase distribution when irradiated with linearly polarized light with a working wavelength of λ.

[0026] As an example, for the incident light E0 with y-direction linear polarization of λ=915nm, the geometric parameters of the lower elliptical nanorods that can achieve the above function are: x1 =246nm,D y1 =166nm,h1=715nm,S x1 =S y1 =650nm; the geometric parameters of the upper elliptical nanocolumn are: S x2 =S y2 =650nm, choose the appropriate major axis D x2 and short axis D y2 The phase of the x and y polarization directions required under high transmission can be obtained

[0027] Figure 5 (a) and (b) respectively represent the elliptical nanorods in the amplitude adjustment layer in the embodiment of the present invention, and the amplitudes of the two orthogonal polarization components of the light field (|E x |,|E y |) and phase response As θ changes. Figure 5 (a) It can be seen that when θ changes in the range of 0°≤θ≤45°, the normalized amplitudes of the x and y components of the light field can change between 0 and 1, and satisfy |E x|=|E0|sinθ、|E y |=|E0|cosθ. In addition, from Figure 5 (b) It can be seen that the change in the angle of the elliptical nanorods in the amplitude adjustment layer does not change the phase response distribution of the light field.

[0028] For the phase adjustment layer, a phase response database can be established by scanning the structure of the elliptical nanocolumns of the phase adjustment layer, and then a suitable long axis D can be selected for each upper elliptical nanocolumn according to the required phase response distribution from the phase response database. x2 and short axis D y2 .like Figure 6 As shown, in this embodiment, the long axis and short axis of the elliptical nanorods in the phase adjustment layer are scanned from 60nm to 460nm, and the phase response under high transmittance conditions is obtained. distribution, which has completely covered the range of 0 to 2π. Among them, Figure 6 (a) is to satisfy the phase response The corresponding major axis distribution is Figure 6 (b) is to satisfy the phase response The corresponding short axis distribution. The phase response can be selected according to the control requirements of the two orthogonal polarization components. And further according to the required phase response Select the corresponding long axis D of the elliptical nanorod x2 and short axis D y2 In this embodiment, the x-polarization component of the outgoing light field is the effective control light field, and the y-polarization component can be filtered out by polarization analysis.

[0029] Figure 7 Schematic diagram of the comparison between the metasurface structure in which both the light field amplitude and phase are adjustable in this embodiment and the conventional method of only adjusting the phase. Figure 7 (a) shows the numerical simulation results of the transmission process of the one-dimensional Airy beam generated by the plane wave modulation of the metasurface structure with adjustable light field amplitude and phase in this embodiment, and the white dotted line represents the theoretically expected main lobe deflection trajectory. Figure 7 (b) shows the numerical simulation result of the propagation process of a rough Airy beam obtained by conventional method, that is, only by phase control of the plane wave. Figure 7 (c) shows the comparison between the lateral light field intensity distribution near the exit surface obtained by the structure of this embodiment (blue dotted line) and the theoretical result (red solid line). Figure 7(d) shows the comparison between the lateral light field intensity distribution near the exit surface obtained by the conventional method (blue dashed line) and the theoretical result (red solid line). By comparing the two, it can be seen that the light beam generated by the metasurface structure of this embodiment is very close to the theoretical expectation in terms of both intensity distribution and main lobe deflection trajectory, and compared with the conventional method of only performing phase control, the light beam generated by the metasurface structure of this embodiment has obvious quality improvements in terms of light field distribution and transmission properties. Therefore, it can be seen that the metasurface structure of this embodiment is conducive to fine control of the light field.

[0030] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A metasurface structure capable of adjusting both the amplitude and phase of a light field, characterized in that: The invention comprises a substrate layer (1), an amplitude adjustment layer (2) and a phase adjustment layer (3); the lower end surface and the upper end surface of the substrate layer (1) are respectively provided with the amplitude adjustment layer (2) and the phase adjustment layer (3); the amplitude adjustment layer (2) is composed of a plurality of elliptical nanocolumns (21) of the same specifications but arranged at different angles; the phase adjustment layer (3) is composed of a plurality of elliptical nanocolumns (31) of different specifications; the arrangement angle of the nanocolumns (21) of the amplitude adjustment layer (2) is determined according to the amplitude of the desired light field, and the size of the nanocolumns (31) of the phase adjustment layer (3) is determined according to the phase of the desired light field; Among them, for the incident light E0 with y-direction linear polarization of λ=915nm, the geometric parameters of the lower elliptical nanorods are: D x1 =246nm,D y =166nm, h1=715nm, S x1 =S y1 =650nm; the geometric parameters of the upper elliptical nanocolumn are: S x2 =S y2 =650nm, choose the appropriate major axis D x2 and short axis D y2 The phase of the x and y polarization directions required under high transmission can be obtained , .

2. The metasurface structure capable of adjusting both the amplitude and phase of a light field according to claim 1, characterized in that: The amplitude adjustment layer (2) and the phase adjustment layer (3) are both made of high refractive index and low loss materials.

3. A method for realizing the metasurface structure with adjustable light field amplitude and phase as described in claim 1 or 2, characterized in that: Specifically: Determine the amplitude distribution and phase response distribution requirements under the illumination of linearly polarized light with an operating wavelength of λ; According to the amplitude distribution requirement, determining the placement angle of each nanocolumn of the amplitude adjustment layer to obtain the required amplitude distribution; According to the phase response distribution requirements, the required phase response distribution is obtained by changing the size of the nanorods at the corresponding positions in the phase adjustment layer.

4. The method according to claim 3, characterized in that For the phase adjustment layer, a phase response database is established by scanning the structure of the nanocolumns of the phase adjustment layer, and then the size of each nanocolumn is selected from the phase response database according to the required phase response distribution.

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