CN214954178U - Phase modulator of plasma super-surface etalon structure - Google Patents

Abstract

The utility model relates to the technical field of optical phase modulation, in particular to a phase modulator of a plasma super-surface etalon structure; the structure is characterized in that a pentagonal cylindrical nano periodic array antenna formed by aluminum is arranged on a flat plate made of SiO2 material, the structure can excite Fabry-Perot resonance in a wavelength range of 600-1000 nm, tuning of coupling resonance of LSPR and Fabry-Perot is realized by respectively adjusting LSP and Fabry-Perot parameters, phase control in a full 2 pi range is realized by changing the height and side length of a pentagonal cylinder, and local surface plasmon resonance is tuned for realizing control of reflectivity; this controller can realize the phase modulation of 0 ~ 2 pi scope at 600 ~ 1000nm wavelength range to accomplished the focusing effect at 43 mu m focus, the utility model discloses simple structure, device compact structure easily integrates to current system, and processing is convenient, and is with low costs.

Description

Phase modulator of plasma super-surface etalon structure

Technical Field

The utility model relates to an optics phase modulation technical field especially relates to a phase modulator of super surface etalon structure of plasma.

Background

The traditional refraction type optical element realizes specific phase distribution by utilizing the difference of material refractive indexes or surface shape change, so that a corresponding functional device is constructed, but the problems of large device size, difficult integration, high loss and difficult realization of conformal design in application are prominent, and the research of a super-surface device changes the current situation along with the development of the technology. The super-surface device based on surface plasma utilizes SP local phase modulation, so that the device structure is more compact, the integration to the existing system is easy, the design is simple, and the super-surface device is considered to be a technical means expected to replace the traditional refraction type device. Compared with the traditional optical device, the super-surface device has the advantages of random regulation and control of sub-wavelength scale phase, amplitude and polarization, light weight, easiness in integration, low loss, conformal surface design and the like.

The traditional optical lens has the defects of thick center, spherical aberration and the like, and the imaging and focusing capabilities of an optical system are limited.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a phase modulator of super surface etalon structure of plasma, it is thick to aim at solving traditional optical lens center among the prior art, and spherical aberration and other defects appear in the lens, have restricted optical system's the formation of image and the technical problem of focusing ability.

In order to achieve the above object, the utility model provides a phase modulator of super surface etalon structure of plasma, the phase modulator of super surface etalon structure of plasma includes plasma nanometer antenna array, isolation layer and reflection stratum, the isolation layer with plasma nanometer antenna array fixed connection, and be located the top of plasma nanometer antenna array, the reflection stratum with isolation layer fixed connection, and be located the top of isolation layer.

The plasma nano antenna array is composed of a plurality of pentagonal metal columns, each pentagonal metal column is fixedly connected with the isolation layer, and the pentagonal metal columns are periodically distributed above the isolation layer.

Wherein the length w of the pentagonal side of each pentagonal metal column is 20-220 nm.

The isolation layer is made of silicon dioxide, and the thickness h2 is 200 nm.

The reflecting layer is made of aluminum, and the thickness h3 is 200 nm.

The utility model discloses a phase modulator of super surface etalon structure of plasma, can pass through plasma nanometer antenna array carries out periodic regulation, utilizes the difference that different duty cycle range metal post corresponds the equivalent refractive index, can realize the regulation of transmission phase place equally to construct relevant plane optical device, improve because traditional optical lens center is thick, defects such as spherical aberration appear in the lens, optical system's formation of image and focusing ability have been restricted, because super surface structure levels, work is on same thickness, spherical aberration problem can not appear in consequently the focusing lens based on super surface system realizes.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a graph of the relationship between the side length and the phase of the metal pillar provided by the present invention.

Fig. 2 is a graph showing the variation of the reflection intensity and phase with the side length and wavelength of the metal pillar provided by the present invention.

Fig. 3 is a graph of the relationship between the target phase and the distribution position of the metal pillars.

Fig. 4 is an effect diagram of the lens provided by the present invention after focusing.

Fig. 5 is a schematic structural diagram of a phase modulator of a plasmonic super-surface etalon structure according to the present invention.

1-plasma nano antenna array, 2-isolation layer and 3-reflection layer.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are merely for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. In addition, in the description of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to fig. 1 to 5, the present invention provides a phase modulator of a plasma super-surface etalon structure, the phase modulator of the plasma super-surface etalon structure includes a plasma nano antenna array 1, an isolation layer 2 and a reflection layer 3, the isolation layer 2 is fixedly connected to the plasma nano antenna array 1 and is located above the plasma nano antenna array 1, and the reflection layer 3 is fixedly connected to the isolation layer 2 and is located above the isolation layer.

In the embodiment, the device is a simple periodic structure, the wave band of the localized surface plasmon resonance and the phase delay (0-2 pi) attached to the wave band can be effectively controlled by controlling the structural parameters (array period, metal film thickness and the like) of the super-surface structure unit, a reflection-type super-surface lens with the working wave band of 1000nm is designed and simulated by utilizing the phase regulation characteristic of the super-surface, the design focal length is highly matched with the simulation focal length, and the size of the focal spot is close to the diffraction limit theoretical value.

The structure of the reflection type surface plasmon polariton super-surface structure based on the pentagonal array is composed of a metal-dielectric-metal (MIM) sub-wavelength resonance micro-cavity, aluminum is used as a substrate material, a middle isolation layer is made of silicon dioxide, a top layer is made of periodic pentagonal aluminum metal columns, and phase regulation is achieved through optical path difference generated in the transmission process of light.

Furthermore, continuous phase regulation is realized in the range of 0-2 pi by adopting transmission phase type regulation, the phase regulation is realized by the optical path difference generated in the transmission process of light, and the expression of the phase difference is as follows:

(wherein: is a phase difference; lambda: a wavelength; n)_effIs the equivalent refractive index; d is thickness)

In the embodiment, the phase can be regulated and controlled by adjusting the thickness or the refractive index, so that the incident light can be subjected to full-phase delay (0-2 pi) modulation by combining localized surface plasmon resonance through aluminum nano discs with different side lengths and thicknesses and changing the period, a reflection-type super-surface flat micro-lens is designed and simulated at the wavelength of 1000nm by utilizing the reflection-type microstructure, the designed focal length is highly matched with the simulated focal length, the size of the focal spot is close to the diffraction limit theoretical value, and further simulation results show that the centrifugal perfect focusing of any position of the flat micro-lens can be realized by utilizing the flexible phase regulation and control function of the super-surface.

Further, the plasma nano antenna array 1 is composed of a plurality of pentagonal metal columns, each pentagonal metal column is fixedly connected with the isolation layer 2 and is periodically distributed above the isolation layer 2, and the period P is 1000 nm; the length w of the pentagon side of each pentagonal metal column is 20-220 nm, and continuous phase regulation and control are realized through periodic change of the side length; the isolation layer 2 is made of silicon dioxide, and the thickness h2 is 200 nm; the reflecting layer 3 is made of aluminum, and the thickness h3 is 200 nm; and (3) exciting Fabry-Perot resonance between the plasma nano antenna array 1 and the reflecting layer and in the working wavelength range by taking TM polarized light with the wavelength range of 600-1000 nm as an incident light source.

In this embodiment, fig. 1(a) demonstrates the side length and phase relationship curve of a single pentagonal metal pillar at a height of 350nm, which can achieve a phase transition of almost 2 pi; FIG. 1(b) is a graph showing the relationship between the side length and the reflection intensity when the height of a single pentagonal metal pillar is 350nm, and it can be seen that the reflection intensity value is greater than 0.7. Therefore, by increasing the metal pillar thickness and side length, the full 2 pi real phase transition can be further tuned.

The position of the LSPR can be changed by adjusting the side length of the nanodisk as shown in fig. 2, so that the whole pattern is moved along the wavelength axis, and the results of reflection and phase are obtained by scanning the height and side length of the nanorods using the s-parameter analysis group for scan calculation. Fig. 2(a) - (b) show the variation of the reflection intensity and phase with the side length and wavelength when the metal pillar thickness d is 350 nm; it can be seen that within the parameter ranges, the wavelength is 600-1000 nm, and the design requirements are met. From the scanning results, the height and wavelength are selected to achieve the desired transmission and phase characteristics. The utility model discloses set the operating wavelength for 1000 nm.

Fig. 3 is a graph showing the relationship between the target phase and the distribution positions of the metal pillars, after the required side length of the nanorods is calculated according to the phase and side length data selected in the above steps, the array arrangement of the cells can be determined according to the curve of the given diagram three, and the purpose of generating a specific phase value at a given spatial position is achieved. For focusing, the light rays propagating from the super-surface to the focal plane must interfere constructively, so that the phase shift of each point on the super-surface should satisfy the relation of the expression of phase difference; the construction of the focusing lens can be further completed according to the determined unit side length and unit array arrangement.

Further, placing a circular hole consisting of a PEC (perfect electrical conductor) between the light source and the lens, confining the injection area to a circular metal area, they show a clear field cut-off due to the incident light being blocked by the PEC aperture; the numerical aperture plays a decisive role in the focusing performance in the lens design, and the calculation of the numerical aperture is based on the formula:

(wherein D is the diameter and f is the focal length)

In the present embodiment, the diameter D is 40 μm depending on the selected cell. The focal length f is 43 μm and the numerical aperture of the superlens is calculated to be about 0.421. And then FDTD simulation setting is carried out, the light source is plane wave, the three-axis boundary conditions are all PML, and a z-plane monitor is arranged to record electric field information and energy information at a focal plane.

Far field projection along the propagation axis z shows that the focal length of the metal is about 43um, as shown in fig. 4(a) and 4(b), and the calculated focal length deviates somewhat from the target value of 50um, mainly due to lens size limitations, so that only a small number of nanorods can be used to achieve a 2 pi phase change at the lens radius. Increasing the size of the lens may help to improve the results, while other parameters, such as the period, may also be optimized. Fig. 4(c) shows the effect of focusing, i.e. a focal spot is finally obtained. According to the diffraction limit formula lambda/2 NA of lens, the utility model relates to a diffraction limit is about 1186nm, and it is worth pointing out, when its diffraction limit is close the wavelength, also can realize high resolution formation of image to being less than the object of illumination wavelength. The results show that changing the side length of the nanorod array can control its phase, but in many cases other design requirements, such as phase profile and transmission efficiency, must be considered, and therefore to complete a design that meets these requirements, other parameters, such as height, period and refractive index effects, may also need to be considered.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (5)

1. A phase modulator of a plasma super-surface etalon structure is characterized in that,

the phase modulator of the plasma super-surface etalon structure comprises a plasma nano antenna array, an isolation layer and a reflection layer, wherein the isolation layer is fixedly connected with the plasma nano antenna array and is positioned above the plasma nano antenna array, and the reflection layer is fixedly connected with the isolation layer and is positioned above the isolation layer.

2. The phase modulator of a plasma super surface etalon structure of claim 1,

the plasma nano antenna array is composed of a plurality of pentagonal metal columns, and each pentagonal metal column is fixedly connected with the isolation layer and periodically distributed above the isolation layer.

3. The phase modulator of a plasma super surface etalon structure of claim 2,

the length w of the pentagon of each pentagon metal column is 20-220 nm.

4. A phase modulator according to claim 3 for a plasma super surface etalon structure,

the isolation layer is made of silicon dioxide, and the thickness h2 is 200 nm.

5. The phase modulator of a plasma super surface etalon structure of claim 4,

the reflecting layer is made of aluminum, and the thickness h3 is 200 nm.

Images