CN116299803A - Transmitted light amplitude, phase and polarization independent modulation metasurface device and modulation method - Google Patents

Abstract

The invention provides a transmissive light amplitude, phase and polarization independently modulated metasurface device and modulation method, comprising three layers of metal structure layers and two layers of intermediate dielectric layers, the intermediate layer is arranged between each two layers of the metal structure layer The medium layer, the metal structure layer is a metal micro-nano structure array, the top layer and the bottom layer of the metal micro-nano structure array are metal grating arrays perpendicular to each other, and the middle structure of the metal micro-nano structure array is along the metal micro-nano structure array. A metal split loop antenna with a 45° directional symmetry of the grating array. By controlling the geometric parameters of different three-layer metal metasurfaces, the present invention can independently regulate the amplitude, phase and polarization of the transmitted light, and the modulation of the above three properties is controlled by independent parameters without affecting each other and can be carried out independently . The modulation efficiency can reach more than 92%, expanding the regulation function of the metasurface.

Description

Transmitted light amplitude, phase and polarization independent modulation metasurface device and modulation method

technical field

The invention relates to the technical field of metasurface devices, in particular to a metasurface device and a modulation method for independently modulating the amplitude, phase and polarization of transmitted light.

Background technique

Metasurfaces refer to artificially designed two-dimensional planar materials composed of subwavelength-scale unit structures. Because their properties are not mainly determined by the inherent properties of the constituent materials, they are determined by designing the size, geometry, and spatial distribution of their unit structures. and other parameters, so it can be designed to have properties that materials in nature do not have, such as special permittivity and magnetic permeability. Compared with traditional materials, metasurfaces have the advantages of small size, thinness, controllability, easy processing, and low cost, and can be used to prepare miniaturized, lightweight, and highly integrated optical modulation devices.

In previous work, by designing complex metasurfaces and changing the geometric parameters of the metasurfaces, one or both of the amplitude, phase, and polarization characteristics of the transmitted light waves can be independently modulated. For example, the phase and polarization of the transmitted light can be modulated by using a dielectric metasurface. For example, the phase and polarization of the transmitted light can be modulated by using an anisotropic elliptical silicon pillar structure. By separately adjusting the elliptical silicon pillar along the two main axes The geometric dimension of the direction can control the phase of the outgoing light. Or use a cross-shaped metal metasurface to modulate the amplitude and polarization of the transmitted light, and rotate the cross-shaped metasurface as a whole to adjust the polarization angle of the outgoing ray-polarized light. Alternatively, the metasurface composed of three metal C-rings can realize the modulation of the amplitude and phase of the transmitted light, and the amplitude modulation of the transmitted light can be realized by changing the radius of the metal C-ring.

The above three tasks realize the independent adjustment of phase/polarization, amplitude/polarization and amplitude/phase respectively. When the relevant parameters are modulated, the corresponding amplitude, phase, and polarization state are fixed values, which cannot be modulated according to requirements. So far, no report has been found on the realization of amplitude, phase, and polarization-independent regulation of metasurfaces. Amplitude, phase, and polarization are important intrinsic properties of a beam of electromagnetic waves. Independent regulation of the above three properties will greatly improve the ability of the device to control the beam, which is of great significance in the generation of structured light, beam shaping, and the development of new photonic devices.

Although the existing technology can use the existing metal and dielectric metasurface devices, it can realize the modulation of any one of the properties of amplitude, phase, and polarization, and can also independently regulate two properties, but the above three properties Independent regulation has always been a difficulty.

Contents of the invention

The purpose of the present invention is to provide a transmitted light amplitude, phase and polarization independent modulation metasurface device and modulation method, which can realize the independent regulation of the transmitted light amplitude, phase and polarization state, and greatly expand the modulation function of the metal metasurface. It provides a way for the design and development of various functional devices.

According to an object of the present invention, the present invention provides a transmissive light amplitude, phase and polarization independently modulated metasurface device, comprising three layers of metal structure layers and two layers of intermediate dielectric layers, between each two layers of the metal structure layer is arranged The intermediate dielectric layer, the metal structure layer is a metal micro-nano structure array, the top layer and the bottom layer of the metal micro-nano structure array are metal grating arrays perpendicular to each other, and the middle structure of the metal micro-nano structure array is along and The metal grating array has a direction angle of 45° and is a symmetrical metal split loop antenna.

Further, the metal split loop antenna is a C-shaped loop, a V-shaped antenna or an L-shaped antenna.

Further, the metal micro-nano structure array and the two intermediate dielectric layers together form a Fabry-Perot resonant cavity.

Further, the metal grating array and the metal split loop antenna are made of gold with a thickness of 100 nm.

Further, the intermediate dielectric layer is made of polyimide material with a thickness of 40 μm.

Further, the width w and period d of the metal grating array are 10 μm and 20 μm respectively, and the outer radius and inner radius R and r of the metal split loop antenna are 45 μm and 35 μm, respectively.

According to another object of the present invention, the present invention provides a modulation method for independently modulating metasurface devices of amplitude, phase and polarization of transmitted light, comprising the following steps:

S1, the top layer and the bottom layer of the metal micro-nano structure array are perpendicular to each other, the azimuth angle θ of the grating is defined as the angle between the top layer grating and the x-axis, and the opening angle of the metal split loop antenna is 2α,

S2, define the angle between the u-axis and the x-axis as θ+45°, define the angle between the v-axis and the x-axis as θ-45°, define the C-ring rotation angle δ as the symmetry axis and u-axis of the metal split loop antenna The angle between the C-ring symmetry axis is defined as the angle between the symmetry axis of the metal split loop antenna and the x-axis;

S3, controlling the polarization angle of the transmitted terahertz wave to be θ° by adjusting the azimuth angle θ of the grating;

S4, by adjusting the opening angle 2α of the metal split loop antenna, the phase of the transmitted terahertz wave is changed between 0-360°;

S5, changing the absolute amplitude transmittance of the outgoing terahertz wave between 0° and 45° by changing the rotation angle δ of the C ring between 0° and 45°.

Further, the metal split loop antenna is a C-shaped loop antenna.

Further, the width w and period d of the metal grating array are 10 μm and 20 μm respectively, and the outer radius and inner radius R and r of the metal split loop antenna are 45 μm and 35 μm, respectively.

Further, by adjusting the geometric parameters of the metasurface structure in each layer, the transmitted light is modulated with an amplitude range of 0-1, a phase range of 0-360°, and a polarization angle of 0-180°.

The technical solution of the present invention can independently regulate the amplitude, phase and polarization of the transmitted light by controlling the geometric parameters of different three-layer metal metasurfaces, and the modulation of the above three properties is controlled by independent parameters without affecting each other. Can be done independently. The modulation efficiency can reach more than 92%, expanding the regulation function of the metasurface.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

Fig. 1 is the structural representation of the embodiment of the present invention;

Fig. 2 is a schematic diagram of the working principle of the method-glass cavity formed by the three-layer metal metasurface of the embodiment of the present invention.

Fig. 3 is a top view of the top metal grating layer, the middle metal C-loop antenna layer and the bottom metal grating layer according to the embodiment of the present invention.

Fig. 4 shows the amplitude, phase and polarization modulation of 512 metasurface antennas according to the embodiment of the present invention to transmitted cross-polarized terahertz waves.

Fig. 5 shows the detailed parameters and modulation data of the amplitude modulation series metasurfaces selected by the embodiment of the present invention.

Fig. 6 shows the detailed parameters and modulation data of the phase modulation series metasurfaces selected by the embodiment of the present invention.

Fig. 7 shows the detailed parameters and modulation data of the polarization modulation series metasurfaces selected in the embodiment of the present invention.

Fig. 8 shows the detailed parameters and modulation data of the amplitude and phase modulation series metasurfaces selected by the embodiment of the present invention.

Fig. 9 shows detailed parameters and modulation data of amplitude and polarization modulation series metasurfaces selected in the embodiment of the present invention.

Fig. 10 is the detailed parameters and modulation data of phase and polarization modulation series metasurfaces selected by the embodiment of the present invention.

Fig. 11 shows the detailed parameters and modulation data of the amplitude, phase, and polarization modulation series metasurfaces selected by the embodiment of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In describing the present invention, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", etc. or The positional relationship is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. In addition, the terms "installation", "connection" and "connection" should be interpreted in a broad sense, for example, it can be fixed connection, detachable connection, or integral connection; it can be mechanical connection or electrical connection; it can be It can be directly connected, or indirectly connected through an intermediary, and can be internal communication between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

Example 1

As shown in Figure 1,

A metasurface device for independently modulating the amplitude, phase and polarization of transmitted light, comprising three metal structure layers and two intermediate dielectric layers, wherein the metal structure layer is a metal micro-nano structure array, specifically, the top layer of the metal micro-nano structure array The metal grating array and the bottom layer are perpendicular to each other, as a polarization filter for the incident line polarization and the outgoing cross line polarization component. The middle structure of the metal micro-nano structure array is a metal splitting symmetrical to the direction angle of 45° to the direction of the metal grating array. Loop antenna, the metal split loop antenna can be a C-shaped loop, V-shaped antenna or L-shaped antenna, etc., to achieve cross-polarization conversion and amplitude and phase modulation of the incident ray polarized light, the orientation of the metal split loop antenna in the middle The angle is related to the desired linear polarization angle at the cell. By changing the azimuth angle of the metal grating array and the combination parameters of the metal split loop antenna, such as rotation angle and opening angle, the polarization angle, amplitude and phase of the ray polarized light can be independently modulated.

In this embodiment, the three-layer metal micro-nano structure array and two intermediate dielectric layers together form a Fabry-Perot resonant cavity, so the polarization conversion efficiency can theoretically reach more than 92%, thereby obtaining high modulation efficiency.

The invention uses a three-layer metal metasurface, which can independently regulate the amplitude, phase, and polarization state of the transmitted light. Compared with the modulation of the metasurface in the traditional method, this embodiment can only modulate the amplitude of the transmitted terahertz wave. Compared with the technology of a single property or some two properties in , phase, and polarization, the method of this embodiment increases the modulation dimension of the metasurface, and will greatly expand the wavefront modulation function of the metasurface device on the basis of ensuring high performance.

The three-layer metal metasurface of the invention is composed of three metal structure layers and two dielectric layers. Light waves are incident on the metasurface from left to right, wherein the first and last metal structure layers from left to right are composed of periodic metal gratings, and the middle metal structure layer is composed of metal split loop antennas such as metal C-rings Antenna composition. Between every two metal structure layers is an intermediate dielectric layer. The metal layer and the dielectric layer together constitute a Fapp-like resonant cavity.

表示各次震荡带来的相位差，通过精细调整介质层2和介质层3的厚度，可以使得各个y偏振分量之间发生相干叠加，从而使整个器件获得较高的调制效率。The schematic diagram of the working principle of the F-P-like resonant cavity formed in this embodiment is shown in Figure 2, assuming that the x-polarized terahertz wave is Ex ⁱⁿ incident from the upper layer, and the y-polarized component transmitted through the entire metasurface once is Ey ^t1 , in The y-polarized component resonated once and transmitted in the resonant cavity formed by the upper layer PI is Ey ^t2 , the y-polarized component resonated once and transmitted in the resonant cavity formed by the lower layer PI is Ey ^t3 , and the y-polarized component transmitted through the metasurface is finally The Hertzian wave is equal to the coherent superposition of electric fields of several y-polarized components, expressed by Equation 1, where t and r represent the amplitude transmittance and reflectivity, respectively, and the second and first numbers in the superscript represent the incident from the first medium to the second In the case of two media, the second and first letters of the subscript indicate the incident and transmitted polarization states.

Represents the phase difference caused by each oscillation. By finely adjusting the thickness of the dielectric layer 2 and the dielectric layer 3, coherent superposition can occur between each y-polarized component, so that the entire device can obtain higher modulation efficiency.

Example 2

This embodiment presents the design results of a metasurface device with a working frequency of 0.75 THz for simultaneous and independent modulation of amplitude, phase, and polarization. In this embodiment, the period P of the metasurface is set to 100 μm, the metal grating and metal C-loop antenna are made of gold (Au) with a thickness of 100 nm, and the two intermediate dielectric layers are made of 40 μm thick polyimide material ( PI) to support the interference and constructive interference of transmitted waves with a working frequency of 0.75 THz to obtain higher polarization conversion efficiency.

As shown in FIG. 3 , the top views of the first metal grating layer, the middle metal C-loop antenna layer and the last metal grating layer are respectively shown. Among them, the width w and period d of the metal grating are 10 μm and 20 μm, respectively, the outer radius and inner radius of the metal C-shaped antenna are R and r, respectively, 45 μm and 35 μm, and the first layer and the last layer of metal gratings are perpendicular to each other. Define the azimuth angle θ of the grating as the angle between the first grating and the x-axis, the opening angle of the C ring is 2α, define the axes u and v as shown by the dotted lines in Figure 3, and the angle between the u-axis and the x-axis is θ+45 °, the angle between the v-axis and the x-axis is θ-45°, and the C-ring rotation angle δ is defined as the angle between the symmetry axis and the u-axis of the metal C-loop antenna in the middle layer, and the angle of the C-ring symmetry axis is defined as the C-ring The included angle between the symmetry axis and the x-axis will vary with the azimuth angle of the grating and the rotation angle of the C ring.

The specific modulation method is as follows: by adjusting the azimuth angle θ of the grating, the polarization angle of the transmitted terahertz wave can be controlled to be θ°; by adjusting the opening angle 2α of the C-loop antenna, the phase of the transmitted terahertz wave can be between 0-360° By changing the C-ring rotation angle δ from 0° to 45°, the absolute amplitude transmittance of the outgoing terahertz wave can be changed from 0 to 1.

Example 3

In order to demonstrate the modulation effect of the metasurface designed by this method on the transmitted terahertz wave, 512 representative metasurfaces were selected to form the metasurface library, and their amplitude, phase, and polarization modulation on the transmitted terahertz wave are shown in Figure 4 , the metasurface in the metasurface library can realize the modulation of transmitted terahertz wave amplitude from 0-1, phase modulation from 0-315°, and polarization modulation from 0-315°. Just select the metasurface series that meets the modulation requirements in the surface library. As an example, this embodiment selects 7 different modulation series antennas, and each modulation series is composed of 8 metasurface basic units, wherein, the period of each metasurface basic unit, grating width, grating period, C ring inner and outer radius However, the azimuth angle θ of the grating, the rotation angle δ of the C ring, the opening angle of the C ring 2α, and the angle of the symmetry axis of the C ring need to be changed accordingly. Now we will introduce each modulation series separately.

1. Amplitude modulation series metasurfaces: As shown in Figure 5, the grating azimuth angle θ of the 8 metasurfaces in this series is fixed at 0°, which means that the transmitted terahertz wave polarization angle is 0°; the 8 metasurfaces The opening angles 2α of the C-rings are all 120°, that is, the phase modulation of the transmitted terahertz wave is a fixed value, about 100°, and the absolute error of the phase modulation is 5°; by changing the rotation angles of the C-rings of the 8 metasurfaces δ varies from 2.5° to 45°, so that the transmitted terahertz wave obtains amplitude modulation in the range of 0 to 1.

2. Phase modulation series of metasurfaces: As shown in Figure 6, the grating azimuth angle θ of the 8 metasurfaces of this series is fixed at 0°, that is to say, the polarization angle of the transmitted terahertz wave is 0°; the 8 metasurfaces The rotation angle δ of the C rings is 10°, that is, the amplitude modulation of the transmitted terahertz wave is a fixed value, about 0.85, and the error of the amplitude modulation is 0.15; by changing the C ring opening angle 2α of the 8 metasurfaces, and The angle of the symmetry axis of the C ring enables the transmitted terahertz wave to obtain a phase modulation of 0-315°.

3. Polarization modulation series metasurfaces: As shown in Figure 7, the C-ring opening angles 2α of the eight metasurfaces in this series are all 146.4°, that is, the phase modulation of the transmitted terahertz wave is a fixed value, about 45° ; The C-ring rotation angle δ of the 8 metasurfaces is all 10°, that is, the amplitude modulation of the transmitted terahertz wave is a fixed value, about 0.95; the azimuth angle θ of the 8 metasurfaces is between 0° and 315° Change, so that the polarization angle of the transmitted terahertz wave also changes within this range.

4. Amplitude and phase modulation metasurface series: As shown in Figure 8, the grating azimuth angle θ of the eight metasurfaces in this series is fixed at 0°, that is to say, the transmitted terahertz wave polarization angle is 0°; By changing the C-ring opening angle 2α and the C-ring rotation angle δ of the metasurface, both the amplitude and phase of the transmitted terahertz wave are modulated, and the amplitude varies between 0-1, while the phase varies between 0-315°.

5. Amplitude and polarization modulation metasurface series: As shown in Figure 9, the C-ring opening angle 2α of the 8 metasurfaces in this series is fixed at 120°, so that the phase of the transmitted terahertz wave is a fixed value, about 102° ; By simultaneously changing the C-ring rotation angle δ and the grating azimuth angle θ of the metasurface, both the amplitude and the polarization angle of the transmitted terahertz wave are modulated, and the amplitude varies between 0-1, while the polarization angle ranges from 0-315° change between.

6. Phase and polarization modulation metasurface series: As shown in Figure 10, the C-ring rotation angle δ of the 8 metasurfaces in this series is fixed at 10°, so that the amplitude modulation of the transmitted terahertz wave is a fixed value, about 0.85 ; By simultaneously changing the C-ring opening angle 2α of the metasurface and the grating azimuth angle θ, the phase and polarization angle of the transmitted terahertz wave are modulated, and the phase varies between 315° and 0°, while the polarization angle is between 0- Change between 315°.

7. Amplitude, phase, polarization modulation metasurface series: As shown in Figure 11, the C-ring rotation angle δ of the 8 metasurfaces in this series is fixed at 10°, so that the amplitude modulation of the transmitted terahertz wave is a fixed value, about is 0.85; by simultaneously changing the C-ring rotation angle δ, C-ring opening angle 2α and grating azimuth θ of the metasurface, the amplitude, phase and polarization angle of the transmitted terahertz wave are all modulated, and the amplitude modulation is between 1-0 The phase modulation varies between 315° and 0°, and the polarization angle varies between 0-315°.

In summary, the present invention can independently regulate the amplitude, phase and polarization of the transmitted light by controlling the geometric parameters of different three-layer metal metasurfaces, and the modulation of the above three properties is controlled by independent parameters, independent of each other. effects can be performed independently.

The present invention uses a three-layer metal metasurface, and by adjusting the geometric parameters of the metasurface structure in each layer, the transmitted light can be adjusted with an amplitude range of 0-1, a phase range of 0-360°, and a polarization angle of 0-180°. Modulation, the above modulations are independent of each other and do not affect each other. The modulation efficiency can reach more than 92%, which expands the control function of the metasurface and provides methods and approaches for the development of various new metasurface devices.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. Transmitted light amplitude, phase and polarization independent modulation metasurface device, it is characterized in that, comprise three layers of metal structure layer and two layers of intermediate medium layer, be provided with described intermediate medium layer between every two layers of described metal structure layers, The metal structure layer is a metal micro-nano structure array, the top layer and the bottom layer of the metal micro-nano structure array are metal grating arrays perpendicular to each other, and the middle structure of the metal micro-nano structure array is along the direction of the metal grating array. A metal split loop antenna with 45° directional symmetry. 2. The transmitted light amplitude, phase and polarization independently modulated metasurface device according to claim 1, wherein the metal split loop antenna is a C-shaped loop, a V-shaped antenna or an L-shaped antenna. 3. The transmitted light amplitude, phase and polarization independently modulated metasurface device according to claim 1, wherein the metal micro-nano structure array and the two layers of the intermediate dielectric layer together form a Fabry-Perot resonance cavity. 4. The transmitted light amplitude, phase and polarization independently modulated metasurface device according to claim 1, wherein the metal grating array and the metal split loop antenna are made of gold with a thickness of 100 nm. 5 . The metasurface device for independently modulating transmitted light amplitude, phase and polarization according to claim 1 , wherein the intermediate dielectric layer is made of polyimide material with a thickness of 40 μm. 6. The transmitted light amplitude, phase and polarization independently modulated metasurface device according to claim 1, wherein the width w and period d of the metal grating array are respectively 10 μm and 20 μm, and the metal split loop antenna The outer and inner radii of R and r are 45 μm and 35 μm, respectively. 7. A modulation method for transmitting light amplitude, phase and polarization independent modulation metasurface device, is characterized in that, comprises the steps: S1, the top layer and the bottom layer of the metal micro-nano structure array are perpendicular to each other, the azimuth angle θ of the grating is defined as the angle between the top layer grating and the x-axis, and the opening angle of the metal split loop antenna is 2α, S2, define the angle between the u-axis and the x-axis as θ+45°, define the angle between the v-axis and the x-axis as θ-45°, define the C-ring rotation angle δ as the symmetry axis and u-axis of the metal split loop antenna The angle between the C-ring symmetry axis is defined as the angle between the symmetry axis of the metal split loop antenna and the x-axis; S3, controlling the polarization angle of the transmitted terahertz wave to be θ° by adjusting the azimuth angle θ of the grating; S4, by adjusting the opening angle 2α of the metal split loop antenna, the phase of the transmitted terahertz wave is changed between 0-360°; S5, changing the absolute amplitude transmittance of the outgoing terahertz wave between 0° and 45° by changing the rotation angle δ of the C ring between 0° and 45°. 8. The modulation method of the transmitted light amplitude, phase and polarization independent modulation metasurface device according to claim 7, characterized in that the metal split loop antenna is a C-shaped loop antenna. 9. the modulation method of transmitted light amplitude, phase and polarization independent modulation metasurface device according to claim 7, it is characterized in that, the width w and period d of metal grating array are respectively 10 μ m and 20 μ m, the metal split loop antenna The outer and inner radii R and r are 45 μm and 35 μm, respectively. 10. The modulation method of the transmitted light amplitude, phase and polarization independent modulation metasurface device according to claim 7, characterized in that, by adjusting the geometric parameters of the metasurface structure in each layer, the amplitude range of the transmitted light is 0 -1, the phase range is 0-360°, and the polarization angle is 0-180° modulation.

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