CN107272216A - Transmission-type metal Meta Materials light beam polarization distribution transformation device - Google Patents

Abstract

The invention provides a transmissive metal metamaterial beam polarization distribution conversion device, comprising: a dielectric substrate; a metal metamaterial layer disposed on the dielectric substrate; the metal metamaterial layer includes a periodic array of metal particles; a dielectric coating The layer is arranged on the metal metamaterial layer; each metal particle in the periodic array of metal particles has at least one pair of parallel smooth plane sidewalls for forming between adjacent metal particles perpendicular to the direction of the smooth plane sidewalls Fabry-Perot resonator; the metal metamaterial layer contains a periodic array of metal particles with an azimuth angle, and the polarization rotation angle of the incident light is regulated by changing the azimuth angle; or the metal metamaterial layer contains multiple particles with different azimuth angles. A periodic array of metal particles is used to transform the spatial polarization distribution of incident light by changing the spatial arrangement of multiple metal particle periodic arrays. The device has the characteristics of wide band adaptation, high work efficiency, simple device structure and easy preparation.

Description

Transmissive metal metamaterial beam polarization distribution conversion device

technical field

The invention relates to the field of optical devices, in particular to a transmissive metal metamaterial beam polarization distribution conversion device.

Background technique

Compared with traditional optical devices, metamaterial optical devices have attracted widespread attention due to their outstanding advantages such as flexible design of device functions, sub-wavelength effective device thickness, and easy-to-integrate planar device structure. The scheme of using optical metamaterials to transform the polarization distribution of beams has also been reported frequently. According to the types of functional unit materials, the existing metamaterial beam polarization control devices can be divided into two types: dielectric metamaterial polarization control devices and metal metamaterial polarization control devices. Among them, dielectric metamaterials mostly use the Mie resonance in the dielectric particles to adjust the polarization of incident light, while metal metamaterials generally use the surface plasmon resonance in the metal structure to adjust the polarization.

The beam polarization control device based on dielectric metamaterials has extremely low absorption loss when the wavelength is larger than its absorption edge, so the device shows extremely high work efficiency; Exhibits strong absorption and thus cannot work efficiently. For example, silicon, the most common dielectric metamaterial working medium, has a working band limited to more than 1.1 microns, and high-efficiency polarization regulation cannot be achieved in the visible light band. Although some devices using wide-bandgap dielectric materials such as titanium oxide can work in the visible light band, their structural aspect ratios are too large, making preparation extremely difficult and costly, making them difficult to popularize.

Most of the early metal metamaterial beam polarization control devices are composed of single-layer ultra-thin metal nanostructures. Such metamaterial beam polarization control devices based on single-layer ultra-thin metal nanostructures cannot effectively suppress the reflection and absorption of metal structures, so Its efficiency is very low. Multilayer metal nanostructures can generate electrical resonance and magnetic resonance at the same time, which can partially suppress reflection and absorption, and its efficiency is greatly improved compared with the phase control devices of early single-layer ultra-thin metal nanostructures, but the current highest efficiency is still It is less than 50%, and the preparation process of the multilayer metal nanostructure is complicated and the cost is high.

Contents of the invention

(1) Technical problems to be solved

In view of the above technical problems, the present invention provides a transmissive metal metamaterial beam polarization distribution conversion device, which has a wide wavelength band, high working efficiency, simple device structure and is easy to manufacture.

(2) Technical solution

According to one aspect of the present invention, a transmissive metal metamaterial beam polarization distribution conversion device is provided, including:

Dielectric substrate;

A metal metamaterial layer, disposed on the dielectric substrate; the metal metamaterial layer includes a periodic array of metal particles;

A dielectric cladding layer is disposed on the metal metamaterial layer; wherein,

Each metal particle in the periodic array of metal particles has at least one pair of parallel smooth plane sidewalls for forming a Fabry-Perot resonant cavity between adjacent metal particles perpendicular to the direction of the smooth plane sidewalls;

The metal metamaterial layer includes a periodic array of metal particles with an azimuth angle, and the polarization rotation angle of the incident light is regulated by changing the azimuth angle; or

The metal metamaterial layer contains multiple periodic arrays of metal particles with different azimuth angles, and the spatial polarization distribution of incident light is transformed by changing the spatial arrangement of the multiple metal particle periodic arrays.

In some embodiments of the present invention, the metal particles in the periodic array of metal particles are arranged in a rectangular array.

In some embodiments of the present invention, the thickness of the metal particles is not less than one-third of the working wavelength of the incident light in the dielectric cladding layer, for the incident light in the Fabry-Perot resonator cavity form a Fabry-Perot resonance.

In some embodiments of the present invention, by adjusting the distance between the smooth plane sidewalls of the adjacent metal particles, that is, the cavity length of the Fabry-Perot resonant cavity, it is used to change the working wavelength of the beam polarization distribution selection.

In some embodiments of the present invention, the azimuth angle of the periodic array of metal particles is 30°, and the polarization rotation angle of the linearly polarized incident light is 60°.

In some embodiments of the present invention, the metal metamaterial layer includes:

The first periodic array of metal particles, with an azimuth angle of 0°, is located in the first region of the metal metamaterial layer, and the first region includes a first first subregion and a first second subregion distributed diagonally;

The second periodic array of metal particles, with an azimuth angle of 30°, is located in the second region of the metal metamaterial layer, and the second region includes a second first subregion and a second second subregion distributed diagonally;

And the third periodic array of metal particles, with an azimuth angle of -30°, is located in the third region of the metal metamaterial layer, and the third region includes a third first subregion and a third second subregion distributed diagonally;

Wherein, the six sub-regions are centrally symmetrically distributed as a whole, the first one sub-region, the second first sub-region, the third first sub-region, the first two sub-regions, the second second sub-region and the third second sub-region arranged around the center, so as to transform the linearly polarized incident light into a radially polarized vector beam.

In some embodiments of the present invention, the working wavelength range of the beam polarization distribution conversion device is from visible light to microwave band.

In some embodiments of the present invention, the material of the dielectric substrate and the dielectric cladding layer is a non-absorbing medium within the working wavelength band of the beam polarization distribution conversion device.

In some embodiments of the present invention, the material of the dielectric substrate and the dielectric coating layer is silicon dioxide or aluminum oxide.

In some embodiments of the present invention, the material of the metal particles is gold, silver, copper, aluminum or a combination thereof.

(3) Beneficial effects

It can be seen from the above technical solution that a transmissive metal metamaterial beam polarization distribution conversion device of the present invention has at least one of the following beneficial effects:

(1) Compared with the existing metal metamaterial beam polarization distribution conversion device, the present invention avoids the high-loss surface plasmon resonance of the metal structure, and utilizes the high-transmission Fabry-Perot in the periodic array of metal particles Resonance and array azimuth are used to realize the transformation of beam polarization distribution, which improves work efficiency;

(2) The thickness of the metal metamaterial layer of the metal metamaterial beam polarization distribution conversion device provided by the present invention is on the sub-wavelength level, which can be integrated with other optical devices, which is conducive to improving the integration of the optical system, and the device structure is simple, easy to prepare;

(3) By adjusting the distance between the smooth plane side walls of adjacent metal particles, that is, the cavity length of the Fabry-Perot resonator, the selection of the working wavelength of the beam polarization distribution conversion device is realized, so that the beam polarization distribution conversion device It can be applied to a wider wave band without being limited by the band gap of the dielectric material.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of a transmissive metal metamaterial beam polarization distribution conversion device in the first embodiment of the present invention.

Fig. 2a is a schematic top view of a periodic array structure of metal particles with an azimuth angle θ=30° in the metal metamaterial layer in the first embodiment of the present invention.

2b is a schematic top view of a periodic array structure of metal particles with an azimuth angle θ=0° in the metal metamaterial layer in the first embodiment of the present invention.

2c is a schematic top view of a periodic array structure of metal particles at an azimuth angle θ=-30° in the metal metamaterial layer in the first embodiment of the present invention.

3 is a graph showing the relationship between the azimuth angle of the periodic array of metal particles and the polarization rotation angle of linearly polarized incident light in the first embodiment of the present invention.

4 is a schematic diagram of the structure of a metal metamaterial layer for transforming a linearly polarized incident beam into a radially polarized vector beam composed of periodic arrays of metal particles with different azimuth angles in the second embodiment of the present invention.

【Symbol Description】

1 Dielectric substrate; 2 Metal metamaterial layer; 3 Dielectric cladding layer;

4.7 Periodic array of metal particles with azimuth angle θ=0°;

5.8 Periodic array of metal particles with azimuth angle θ=30°;

6,9 A periodic array of metal particles with an azimuth angle θ=-30°.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

It should be noted that, in the drawings or descriptions of the specification, similar or identical parts all use the same figure numbers. Implementations not shown or described in the accompanying drawings are forms known to those of ordinary skill in the art. Additionally, while illustrations of parameters including particular values may be provided herein, it should be understood that the parameters need not be exactly equal to the corresponding values, but rather may approximate the corresponding values within acceptable error margins or design constraints. The directional terms mentioned in the embodiments, such as "up", "down", "front", "rear", "left", "right", etc., are only referring to the directions of the drawings, and are not intended to limit the present invention protected range.

The invention provides a transmissive metal metamaterial light beam polarization distribution conversion device. Fig. 1 is a schematic cross-sectional structure diagram of a transmissive metal metamaterial beam polarization distribution conversion device in the first embodiment of the present invention, wherein the z coordinate direction represents the vertical direction of the device, and the x and y coordinate directions represent the horizontal direction of the device. Please refer to Fig. 1, the transmissive metal metamaterial beam polarization distribution conversion device proposed by the present invention includes:

dielectric substrate 1;

The metal metamaterial layer 2 is arranged on the dielectric substrate, and the metal metamaterial layer includes a periodic metal particle array;

The dielectric coating layer 3 is arranged on the metal metamaterial layer;

Among them, the thickness of the metal metamaterial layer 2 is on the order of sub-wavelength, which can be integrated with other optical devices, which is beneficial to improve the integration degree of the optical system, and the device has a simple structure and is easy to manufacture.

The metal particles in the periodic array of metal particles contained in the metal metamaterial layer 2 are arranged in a rectangular array, and each metal particle in the periodic array of metal particles has at least one pair of parallel smooth plane side walls and the thickness is not less than the incident One-third of the working wavelength of light in the dielectric cladding layer is used to form a Fabry-Perot resonant cavity between adjacent metal particles in a direction perpendicular to the sidewall of the smooth plane.

Compared with the existing metal metamaterial beam polarization distribution conversion device, the present invention avoids the high-loss metal structure surface plasmon resonance, and utilizes the high-transmission Fabry-Perot resonance in the periodic array of metal particles and the array The azimuth angle is used to realize the transformation of the beam polarization distribution. After the incident light is scattered by the metal particles, it is coupled into the Fabry-Perot resonant cavity to form a transverse Fabry-Perot resonance, thereby realizing transformation of the polarization distribution of the light beam and improving work efficiency.

By changing the size of the particles to adjust the width of the Fabry-Perot resonator, thereby adjusting the confinement factor of the resonator, and then adjusting the polarization directions parallel to and perpendicular to the transmitted light components of the Fabry-Perot resonator. phase delay.

By adjusting the distance between the smooth plane side walls of adjacent metal particles, that is, the cavity length of the Fabry-Perot resonant cavity, the selection of the working wavelength of the transmissive metal metamaterial beam polarization distribution conversion device is realized, so that the working of the device The wavelength is tuned to any wavelength from visible light to microwave band, and the working wavelength of the light beam polarization distribution conversion device is also the working wavelength of incident light in the dielectric cladding layer. The material of the metal particles is gold, silver, copper, aluminum or a combination thereof.

The dielectric substrate and the dielectric cladding layer are used to provide support and protection for the metal metamaterial layer and impedance matching between the external environment and the metal particles, and the materials thereof are selected according to the working band of the metal metamaterial beam polarization distribution conversion device, so as to Ensure that the dielectric material has no absorption in the working band, such as silicon dioxide or aluminum oxide.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

1. The first embodiment

In this embodiment, the metal metamaterial layer includes a periodic array of metal particles with an azimuth angle, and the polarization rotation angle of the incident light is regulated by changing the azimuth angle. Fig. 2 a is a schematic top view of a periodic array structure of metal particles with an azimuth angle θ=30° in the metal metamaterial layer in the first embodiment of the present invention, and Fig. 2 b is a schematic top view of the metal metamaterial layer in the first embodiment of the present invention with an azimuth angle θ= A schematic top view of a periodic array structure of metal particles at 0°, and Figure 2c is a schematic top view of a periodic array structure of metal particles with an azimuth angle θ=-30° in the metal metamaterial layer in the first embodiment of the present invention, wherein the metal particles are along the length The period of the axis direction is P1, the period of the metal particle along the short axis direction is P2, the length of the long axis of the particle is 1, the length of the short axis is w, and the angle between the long axis direction of the particle and the x-axis direction of the coordinate axis shown in the figure is the metal particle The azimuth angle θ of the periodic array, the azimuth angle ranges from -90° to 90°.

As shown in Figure 2a, Figure 2b and Figure 2c, the shape of the metal particles in the metal metamaterial layer is a cuboid, and the two opposite planes where the long axes of the metal particles are located are a pair of parallel smooth plane side walls, along the vertical direction to the smooth A Fabry-Perot resonant cavity is formed between adjacent metal particles in the direction of the plane side wall (that is, the direction of the short axis of the particle). The linearly polarized incident light is decomposed into a component parallel to the long axis of the particle and a component perpendicular to the long axis of the particle. Since the metal particles are thick enough, that is, the thickness of the metal particles is not less than one-third of the working wavelength of the incident light in the dielectric coating layer, the component parallel to the long axis direction of the particles is scattered in the Fabry through inter-particle scattering coupling. A standing wave is formed in the Perot resonator to obtain high transmittance and phase delay. The component perpendicular to the long axis of the particle does not interact strongly with the periodic array of metal particles, so high transmission and a certain phase delay are also obtained.

By adjusting the length of the long axis of the particle, the phase delay between the component parallel to the long axis of the particle and the transmitted component perpendicular to the long axis of the particle is π, so the transmitted light is still linearly polarized light.

For a periodic array of metal particles with different azimuth angles, the amplitude of the light component perpendicular to the long axis of the particle is different from that parallel to the long axis of the particle, so the incident light of the same polarization state passes through the periodic array of metal particles with different azimuth angles. The angle of polarization rotation after the array is different. 3 is a graph showing the relationship between the azimuth angle of the periodic array of metal particles and the polarization rotation angle of linearly polarized incident light in the first embodiment of the present invention. Please refer to Figure 3. After the linearly polarized incident light passes through the metal periodic array with azimuth angles of 30°, 0°, and -30°, the polarization rotation angles of the linearly polarized incident light are 60°, 0°, and -60°, respectively.

Two, the second embodiment

In this embodiment, the metal metamaterial layer contains a plurality of periodic arrays of metal particles with different azimuth angles, and the linearly polarized incident beam is converted into a radially polarized light beam by changing the spatial arrangement of the periodic arrays of multiple metal particles Vector light beam.

The material of the dielectric substrate and the dielectric cladding layer of the device is quartz, and the material of the metal particles is silver. The size of the metal particles is: long axis length l=340nm, short axis length w=200nm, particle thickness h=360nm. The period of the metal particles along the long axis direction is P1=600nm, the period of the metal particles along the short axis direction is P2=620nm, and the operating wavelength of the device is 1.1 μm.

Fig. 4 is a schematic diagram of the metal metamaterial layer structure composed of periodic arrays of metal particles with different azimuth angles in the second embodiment of the present invention, which transforms the linearly polarized incident beam into a radially polarized vector beam. Please refer to Fig. 4, the entire metal metamaterial The layer is composed of 6 areas, namely area 4, area 5, area 6, area 7, area 8, and area 9. Areas of different colors contain periodic arrays of metal particles with different azimuth angles. Among them:

Area 4 and area 7 contain a periodic array of metal particles with an azimuth angle θ = 0°, and the polarization rotation angle for linearly polarized light incident along the x-axis direction shown in the figure is 0°, and the double-headed arrows in the corresponding areas indicate transmission The polarization direction of the light;

Areas 5 and 8 contain a periodic array of metal particles with an azimuth angle θ = 30°, and the polarization rotation angle for linearly polarized light incident along the x-axis direction shown in the figure is 60°, and the double-headed arrows in the corresponding areas indicate transmission The polarization direction of the light;

Areas 6 and 9 contain a periodic array of metal particles with an azimuth angle θ=-30°, and the polarization rotation angle for linearly polarized light incident along the x-axis direction shown in the figure is -60°, corresponding to the double-headed arrows in the area Indicates the polarization direction of the transmitted light.

After the linearly polarized light whose polarization direction is along the x-axis in Figure 4 is vertically incident on the surface of the device, the outgoing beam is transformed into a radially polarized vector beam.

So far, the present embodiment has been described in detail with reference to the drawings. Based on the above description, those skilled in the art should have a clear understanding of a transmissive metal metamaterial beam polarization distribution conversion device of the present invention.

It should be noted that, in the accompanying drawings or in the text of the specification, implementations that are not shown or described are forms known to those of ordinary skill in the art, and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and those skilled in the art can easily modify or replace them.

It should also be noted that the text may provide examples of parameters that include specific values, but these parameters need not be exactly equal to the corresponding values, but may approximate the corresponding values within acceptable error tolerances or design constraints. The directional terms mentioned in the embodiments, such as "up", "down", "front", "rear", "left", "right", etc., are only referring to the directions of the drawings, and are not intended to limit the present invention protected range. The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A transmission type metal metamaterial light beam polarization distribution conversion device comprises:

a dielectric substrate;

the metal metamaterial layer is arranged on the dielectric substrate; the metal metamaterial layer comprises a periodic array of metal particles;

the medium coating layer is arranged on the metal metamaterial layer; wherein,

each metal particle in the metal particle periodic array at least has a pair of parallel smooth plane side walls, and a Fabry-Perot resonant cavity is formed between adjacent metal particles in the direction perpendicular to the smooth plane side walls;

the metal metamaterial layer comprises a metal particle periodic array with an azimuth angle, and the polarization rotation angle of incident light is regulated by changing the azimuth angle; or

The metal metamaterial layer comprises a plurality of metal particle periodic arrays with different azimuth angles, and the spatial polarization distribution of incident light is changed by changing the spatial arrangement mode of the plurality of metal particle periodic arrays.

2. The device of claim 1, wherein the metal particles in the periodic array of metal particles are arranged in a rectangular array.

3. The device of claim 2, wherein the thickness of the metal particles is not less than one third of the operating wavelength of the incident light in the dielectric cladding layer, so that the incident light forms a fabry-perot resonance in the fabry-perot resonator.

4. The device of claim 3, wherein the distance between the smooth planar sidewalls of the adjacent metal particles, i.e. the cavity length of the Fabry-Perot resonator, is adjusted to select the operating wavelength of the device.

5. The device of claim 1, wherein the periodic array of metal particles has an azimuthal angle of 30 ° and the incident light with linear polarization is rotated by a polarization angle of 60 °.

6. The device of claim 1, wherein the metallic metamaterial layer comprises:

the first metal particles are periodically arrayed, the azimuth angle is 0 degrees, and the first metal particles are positioned in a first area of the metal metamaterial layer, and the first area comprises a first sub-area and a first second sub-area which are diagonally distributed;

the second metal particles are periodically arrayed, the azimuth angle is 30 degrees, and the second metal particles are positioned in a second area of the metal metamaterial layer, and the second area comprises a second first subregion and a second subregion which are diagonally distributed;

the third metal particle periodic array is positioned in a third area of the metal metamaterial layer, and the azimuth angle of the third metal particle periodic array is-30 degrees, and the third area comprises a third first sub-area and a third second sub-area which are distributed diagonally;

the six sub-regions are integrally distributed in a central symmetry manner, and the first sub-region, the second sub-region, the third sub-region, the first second sub-region, the second sub-region and the third second sub-region are sequentially arranged around the center, so that linear polarization incident light is converted into radial polarization vector light beams.

7. The device of claim 1, wherein the wavelength range of the device is from visible to microwave.

8. The device of claim 1, wherein the dielectric substrate and the dielectric cladding layer are made of a non-absorptive medium within an operating band of the device.

9. The metal metamaterial wave plate of claim 8, wherein the dielectric substrate and the dielectric cladding layer are made of silicon dioxide or aluminum oxide.

10. The device of claim 1, wherein the metal particles are made of gold, silver, copper, aluminum or a combination thereof.