CN107238885A - Metal Meta Materials wave plate - Google Patents

Abstract

The invention provides a kind of metal Meta Materials wave plate, including：Dielectric substrate；Metal metamaterial layer, is arranged in dielectric substrate；The metal metamaterial layer includes metallic particles cyclic array；Media packs layer, is arranged in metal metamaterial layer, for providing impedance matching；Wherein, the metallic particles in metallic particles cyclic array is arranged by rectangular array；Each metallic particles in metallic particles cyclic array comprises at least a pair of parallel smooth flat side wall, for forming fabry perot cavity between the adjacent metal particles perpendicular to smooth flat sidewall direction.A kind of metal Meta Materials wave plate of the present invention, possess wide high conversion efficiency, service band, being easily integrated, it is easily prepared the characteristics of.

Description

Metal metamaterial wave plate

technical field

The invention relates to the field of optical devices, in particular to a metal metamaterial wave plate.

Background technique

Polarization is a fundamental property of electromagnetic waves. The information carried by the polarization state is of great value in both signal transmission and sensing measurement. Applications involving polarization control technology have penetrated into all aspects of our daily life and preface science. The wave plate is the most common polarization control device, which can realize the mutual conversion between linearly polarized light, circularly polarized light, and elliptically polarized light, and the rotation of the polarization direction of linearly polarized light. Most of the traditional wave plates are prepared from optical crystals with birefringence characteristics, which use the characteristics of different refractive indices of light components in different polarization directions of birefringent crystals to generate the required phase difference between mutually orthogonal transmitted lights, so as to realize Controlling the polarization state. Due to the weak optical activity of natural crystals, conventional waveplates are not convenient for optical integration.

Emerging metamaterial waveplates have attracted widespread attention due to their sub-wavelength effective device thickness, flexible design of working bands and working bandwidths. Among them, the wave plate based on dielectric metamaterial can realize ultra-wide working bandwidth and close to 100% working efficiency. However, most dielectric metamaterial waveplates use silicon as the working medium. Due to the limited band gap of silicon, this type of waveplate cannot maintain high efficiency in the band above 300 terahertz. Although some devices using wide-bandgap dielectric materials such as titanium oxide can adapt to wider bands, their structural aspect ratios are too large, making them extremely difficult to prepare and costly, making them difficult to popularize. Metal metamaterial-based wave plates can flexibly adjust the working band of the device through the structural design of the material, but this type of wave plate uses the surface plasmon resonance of the metal material, so the loss will be relatively high. At the same time, the wave plate with a single-layer metal nanostructure whose thickness is smaller than the wavelength cannot effectively control the reflection loss, so the efficiency of metal metamaterial wave plates in the optical band is generally low. The use of coupling between multilayer metal metamaterials to simultaneously generate electrical resonance and magnetic resonance to form a Huygens metasurface can improve the efficiency of metal metamaterial wave plates, but the efficiency of metal metamaterial Huygens metasurfaces is still at present. 50% or less, and its structure is complex and difficult to prepare.

Contents of the invention

(1) Technical problems to be solved

In view of the above technical problems, the present invention provides a metal metamaterial wave plate, which has the characteristics of high conversion efficiency, wide operating band, easy integration, and easy preparation.

(2) Technical solution

According to one aspect of the present invention, a metal metamaterial wave plate is provided, comprising:

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, disposed on the metal metamaterial layer, for providing impedance matching;

Wherein, the metal particles in the periodic array of metal particles are arranged in a rectangular array; each metal particle in the periodic array of metal particles includes at least a pair of parallel smooth plane side walls for A Fabry-Perot cavity is formed between adjacent metal particles in the sidewall direction.

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.

In some embodiments of the present invention, the incident light is scattered by the metal particles and then coupled into the Fabry-Perot resonant cavity to form a transverse Fabry-Perot resonance.

In some embodiments of the present invention, the phase delay between the transmitted light components whose polarization directions are respectively parallel to and perpendicular to the Fabry-Perot resonator is adjusted by changing the size of the metal particles.

In some embodiments of the present invention, the metal metamaterial wave plate is a quarter wave plate or a half wave plate.

In some embodiments of the present invention, the shape of the metal particle is a cuboid, and the phase delay between the transmitted light components whose polarization directions are respectively parallel and perpendicular to the Fabry-Perot resonator can be adjusted by changing the long axis length of the metal particle.

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, the working wavelength of the metal metamaterial wave plate is adjusted. select.

In some embodiments of the present invention, the working wavelength range of the metal metamaterial wave plate 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 wave plate.

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

The material of the metal particles is gold, silver, copper or aluminum.

(3) Beneficial effects

It can be seen from the above technical solution that a metal metamaterial wave plate of the present invention has at least one of the following beneficial effects:

(1) Compared with the existing metal metamaterial wave plate, the present invention uses the high transmittance Fabry-Perot resonance to adjust the phase delay generated by the transmitted light, which reduces the reflection and absorption loss of the wave plate, thereby improving the The conversion efficiency of the wave plate;

(2) Compared with traditional wave plates based on optical crystals, the thickness of the metal metamaterial layer of the metal metamaterial wave plate provided by the present invention is on the order of sub-wavelength, which can be integrated with other optical devices, which is conducive to improving the optical system. The degree of integration is high, and the wave plate device has a simple structure and is easy to prepare;

(3) By adjusting the distance between the smooth plane sidewalls of adjacent metal particles, that is, the cavity length of the Fabry-Perot resonator, the selection of the working wavelength of the wave plate is realized, and then the metal metamaterial wave provided by the present invention The chip is suitable for a wider range of bands.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of a metal metamaterial wave plate 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.

Fig. 2 is a top view structural diagram of a metal metamaterial layer in a metal metamaterial wave plate in the first embodiment of the present invention.

FIG. 3 is a curve of the transmittance of the incident light component polarized along the x-axis direction and the polarization along the y-axis direction as a function of the wavelength of the incident light in the first embodiment of the present invention.

FIG. 4 is a curve of the phase difference between the transmitted light component polarized along the x-axis direction and the polarized along the y-axis direction as a function of the wavelength of the incident light in the first embodiment of the present invention.

FIG. 5 is a curve showing the variation of the transmittance of the incident light component along the x-axis direction and the polarization along the y-axis direction with the wavelength of the incident light in the second embodiment of the present invention.

FIG. 6 is a graph showing the variation of the phase difference between the transmitted light components polarized along the x-axis direction and the polarized along the y-axis direction with the wavelength of the incident light in the second embodiment of the present invention.

【Main components】

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

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 metal metamaterial wave plate. FIG. 1 is a schematic cross-sectional view of a metal metamaterial wave plate in the first embodiment of the present invention. Please refer to Figure 1, the metal metamaterial wave plate includes:

dielectric substrate 1;

A metal metamaterial layer 2 is disposed on the dielectric substrate 1; the metal metamaterial layer includes a periodic array of metal particles;

A dielectric cladding layer 3 is disposed on the metal metamaterial layer 2 for providing impedance matching;

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

The metal particles in the periodic array of metal particles are arranged in a rectangular array; each metal particle in the periodic array of metal particles contains at least one pair of parallel smooth plane side walls and the thickness is not less than that of the incident light in the medium One-third of the operating wavelength in the cladding layer is used to form a Fabry-Perot cavity between adjacent metal particles in a direction perpendicular to the smooth planar sidewalls.

The incident light is coupled into the Fabry-Perot resonant cavity after being scattered by the metal particles to form a transverse Fabry-Perot resonance.

The width of the Fabry-Perot resonant cavity is adjusted by changing the size of the metal particles, thereby adjusting the confinement factor of the resonant cavity, and then adjusting the phase delay generated by the transmitted light. Compared with the existing metal metamaterial wave plate, the present invention utilizes the Fabry-Perot resonance with high transmittance to adjust the phase delay generated by the transmitted light, reduces the reflection and absorption loss of the wave plate, and thus improves the wave plate’s performance. conversion efficiency;

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 wave plate is realized, so that the working wavelength of the metal metamaterial wave plate is tuned to From visible light to any wavelength in the microwave band, the working wavelength of the wave plate is also the working wavelength of the incident light in the dielectric cladding layer. The material of the metal particles is gold, silver, copper or aluminum.

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. Materials are non-absorbing, such as silicon dioxide or aluminum oxide.

The metal metamaterial wave plate will be described in detail below in conjunction with FIG. 2 . Fig. 2 is a top view structural diagram of a metal metamaterial layer in a metal metamaterial wave plate in the first embodiment of the present invention. Please refer to Figure 2, the shape of the metal particle is a cuboid, the long axis of the metal particle is along the direction of the x coordinate axis, and the length is 1; the short axis of the metal particle is along the direction of the y coordinate axis, and the length is w; the thickness of the metal particle in the direction of the z axis is h; The period along the x-axis direction is Px; the period of the particle along the y-axis direction is Py.

The two opposite planes where the long axis of the metal particles are located are a pair of parallel smooth plane side walls, and a Fabry-Perot resonant cavity is formed between adjacent metal particles along the y-coordinate direction (ie, the short axis direction of the particles). Since the metal particles are sufficiently thick, 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 cladding layer, the incident light component polarized along the x-axis direction can be coupled to the Fabry-Perot resonance by scattering A standing wave forms in the cavity and is transmitted with high efficiency while producing an additional phase delay. However, the incident light component polarized along the y-axis direction has no strong interaction with the metal metamaterial layer, and can also penetrate the metal metamaterial layer with high efficiency, while producing a small fixed additional phase delay. The phase delay of the transmitted light component polarized along the x-axis direction can be adjusted by adjusting the length of the long axis of the metal particles, thereby adjusting the phase delay between the two transmitted light components polarized along the x-axis direction and the y-axis direction. Through the design of the structural parameters of the periodic array of metal particles, the phase difference of 90° and 180° can be obtained in the range from visible light to microwave, so as to realize the functions of quarter-wave plate and half-wave plate.

A metal metamaterial wave plate provided by the present invention will be further described in detail below in conjunction with specific embodiments.

1. The first embodiment

The metal metamaterial wave plate in this embodiment is a half-wave plate, which can rotate the polarization direction of incident light by 90 degrees, its working wavelength is 1.1 um, and its transmission efficiency is above 80%. The material of the dielectric substrate and the dielectric cladding layer of the half-wave plate is both quartz, and the material of the metal particles is silver. The size of the metal particle is: long axis length l=340nm, short axis length w=200nm, height h=360nm. The metal particle period along the x-axis direction is Px=600nm, and the period along the y-axis direction is Py=620nm.

The polarization direction of the incident light forms an angle of 45 degrees with the long axis and is perpendicular to the wave plate, so the intensity of the incident light component in the direction parallel to the long axis and the short axis is the same. Figure 3 is the variation curve of the transmittance of the incident light component polarized along the x-axis direction and the polarization along the y-axis direction with the incident light, where Tx represents the transmittance of the incident light component polarized along the x-axis direction, and Ty represents the polarization along the y-axis direction The transmittance of the incident light component in the axial direction. Please refer to Figure 3, the transmittance of the two polarization components is the same at the working wavelength of 1.1um. Fig. 4 is a graph showing the variation of the phase difference between the transmitted light components polarized along the x-axis direction and the polarized along the y-axis direction with the wavelength of the incident light. Please refer to FIG. 4 , at a working wavelength of 1.1um, the phase difference between the transmitted component with polarization along the x-axis and the transmission component with polarization along the y-axis is π. Therefore, the polarization direction of the transmitted light is rotated by 90 degrees relative to the polarization direction of the incident light, and the device realizes the function of a half-wave plate, and its efficiency is above 80%.

Two, the second embodiment

The metal metamaterial wave plate in this embodiment is a quarter wave plate, which can realize mutual conversion between linearly polarized light and circularly polarized light. The working wavelength of the wave plate is 1.1um, and the transmission efficiency is above 80%. The material of the dielectric substrate and the dielectric cladding layer of the quarter-wave plate is both quartz, and the material of the metal particles is silver. The size of the metal particle is: long axis length l=270nm, short axis length w=200nm, height h=360nm. The period of the periodic array of metal particles is: the period along the x-axis direction is Px=600nm, and the period along the y-axis direction is Py=620nm.

The polarization direction of the incident light forms an angle of 45 degrees with the long axis of the metal particle and is perpendicular to the wave plate, so the intensity of the incident light component with the polarization direction parallel to the long axis direction and the polarization direction parallel to the short axis direction is the same. Figure 5 is the variation curve of the transmittance of the incident light component polarized along the x-axis direction and the polarization along the y-axis direction with the wavelength of the incident light, where Tx represents the transmittance of the incident light component polarized along the x-axis direction, and Ty represents the polarization along the x-axis direction The transmittance of the incident light component in the y-axis direction. Please refer to Figure 5, the transmittance of the two polarization components at the working wavelength of 1.1um is basically the same. Fig. 6 is a curve of the phase difference between the transmitted light components polarized along the x-axis direction and the polarized along the y-axis direction as a function of the wavelength of the incident light. Referring to FIG. 6 , at an operating wavelength of 1.1 um, the phase difference between the transmitted component with polarization along the x-axis and the transmitted component with polarization along the y-axis is π/2. Therefore, the transmitted light component polarized along the x-axis direction has the same amplitude as the transmitted light component polarized along the y-axis direction, and the relative phase delay is π/2, and the linearly polarized incident light is converted into circularly polarized light after passing through the wave plate , that is, the device realizes the function of a quarter-wave plate, and its efficiency is above 80%. Compared with the half-wave plate in the first embodiment, the quarter-wave plate in this embodiment is different in that the length of the major axis of the metal particles is reduced. Since the length of the major axis of the metal particles is proportional to the cavity width of the Fabry-Perot resonator, the reduction of the length of the major axis of the metal particles reduces the confinement factor of the resonator, making the polarization along the x-axis direction and the polarization along the y-axis direction The phase delay between transmitted light components is reduced.

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 the metal metamaterial wave plate 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 modify or replace them, for example:

(1) The shape of the metal particle in the specific embodiment is a cuboid, and the metal particle can also be in other shapes, but it needs to have a pair of parallel smooth plane side walls, which does not affect the realization of the present invention;

(2) The structural parameters of the metal particle array can be changed with corresponding working conditions, without affecting the realization of the present invention;

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.

In summary, the metal metamaterial wave plate of the present invention realizes the control of the phase delay of transmitted light through the transverse Fabry-Perot resonance in the periodic array of metal particles, and has the advantages of high conversion efficiency and wide working band. Therefore, it can be widely used in many fields such as sensing and communication.

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 kind of metal Meta Materials wave plate, including：

Dielectric substrate；

Metal metamaterial layer, is arranged in the dielectric substrate；The metal metamaterial layer includes metallic particles cyclic array；

Media packs layer, is arranged in the metal metamaterial layer, for providing impedance matching；

Wherein, the metallic particles in the metallic particles cyclic array is arranged by rectangular array；The metallic particles is periodically Each metallic particles in array comprises at least a pair of parallel smooth flat side wall, for perpendicular to smooth flat side wall side To adjacent metal particles between form fabry perot cavity.

2. a kind of metal Meta Materials wave plate according to claim 1, wherein, the thickness of the metallic particles is not less than incidence Light the media packs layer in operation wavelength 1/3rd.

3. a kind of metal Meta Materials wave plate according to claim 1, wherein, coupling after incident light is scattered by the metallic particles Close and horizontal Fabry Perot resonance is formed in Fabry Perot resonant cavity.

4. a kind of metal Meta Materials wave plate according to claim 1, wherein, by change the size of the metallic particles come Regulation polarization direction is parallel and perpendicular to the phase delay between the transmission light component of fabry perot cavity respectively.

5. a kind of metal Meta Materials wave plate according to claim 1, wherein, the metal Meta Materials wave plate is a quarter Wave plate or half-wave plate.

6. a kind of metal Meta Materials wave plate according to claim 1, wherein, metallic particles is shaped as cuboid, passes through Change the long axis length of metallic particles to adjust the transmitted light that polarization direction is parallel and perpendicular to fabry perot cavity respectively Phase delay between component.

7. a kind of metal Meta Materials wave plate according to claim 1, wherein, by the light for adjusting the adjacent metal particles The distance between sliding flat sidewall, i.e. the chamber of fabry perot cavity is long, realizes to the metal Meta Materials wave plate operation wavelength Selection.

8. a kind of metal Meta Materials wave plate according to claim 1, wherein, the metal Meta Materials wave plate operation wavelength model Enclose for visible ray to microwave band.

9. a kind of metal Meta Materials wave plate according to claim 1, wherein, the dielectric substrate and the material of media packs layer Expect for the medium without absorption in the wave plate service band.

10. a kind of metal Meta Materials wave plate according to claim 1, wherein, the material of the metallic particles is gold, silver, Copper or aluminium.