阅读说明：本技术 一种太赫兹自旋选择性传输全硅超构器件设计方法 (Design method of terahertz spin selective transmission all-silicon super-structure device ) 是由 李继涛 岳震 李�杰 郑程龙 于 2021-05-28 设计创作，主要内容包括：本发明公开了一种太赫兹自旋选择性传输全硅超构器件设计方法,包括S1、基于全硅有损材料构建基本结构,基本结构包括三个几何分布的椭圆条；S2、将S1中的基本结构进行周期延伸形成超表面。本发明强化太赫兹波与硅的相互作用,设计了自旋选择性透射全硅超表面,在太赫兹波段获得了优良的自旋选择性传输特性,圆二色性可达0.4,相比现有技术,本发明将自旋选择透射全硅超表面的圆二色性提高了30％左右。(The invention discloses a design method of a terahertz spin selective transmission all-silicon super-structure device, which comprises the steps of S1, constructing a basic structure based on all-silicon lossy materials, wherein the basic structure comprises three geometrically distributed elliptical strips; and S2, periodically extending the basic structure in the S1 to form a super surface. The invention strengthens the interaction between the terahertz wave and the silicon, designs the spin selective transmission all-silicon super-surface, obtains excellent spin selective transmission characteristic in the terahertz wave band, and has circular dichroism reaching 0.4, compared with the prior art, the invention improves the circular dichroism of the spin selective transmission all-silicon super-surface by about 30 percent.)

1. A design method of a terahertz spin selective transmission all-silicon super-structure device is characterized by comprising the following steps:

s1, constructing a basic structure based on the all-silicon lossy material, wherein the basic structure comprises three geometrically distributed elliptical strips;

and S2, periodically extending the basic structure in the S1 to form a super surface.

2. The design method of the terahertz spin selective transmission all-silicon metamaterial according to claim 1, wherein: the all-silicon is high-resistance silicon.

3. The design method of the terahertz spin selective transmission all-silicon metamaterial according to claim 1, wherein: two of the three elliptical strips are completely the same in size, and the two elliptical strips with the same size are arranged in pairs and form an inclined included angle of 45 degrees with the third elliptical strip; the major axis of the third elliptical strip is the same as the major axes of the other two elliptical strips, and the minor axes are different.

Technical Field

The invention belongs to the technical field of novel artificial electromagnetic materials and terahertz scientific technology, and particularly relates to a design method of a terahertz spin selective transmission all-silicon super-structure device.

Background

In recent years, researchers design a super surface with a specific structure to realize selective transmission and reflection of circularly polarized light in different spin directions, and the characteristic can be used for preparing asymmetric filters and optical anti-counterfeiting devices and can be applied to optical communication, quantum optics and optical sensing. Circular dichroism is a key index for evaluating spin-selective propagation characteristics, and in general, by constructing a chiral structure using a layer of a metal material, spin-selective transmission through a super-surface can be achieved. However, to obtain strong circular dichroism, it is often necessary to further rely on multilayer metal designs. In addition, composite all-dielectric (e.g., silicon and silica system, or silica and titania system) micro-nano structures are also good choices for achieving strong circular dichroism. The all-silicon super-surface (without compounding other materials) is one of all-dielectric super-surfaces, and has the advantages of high refractive index and low loss, and has rich sources and mature processing technology. Compared with the composite all-dielectric super surface, the preparation process of the all-silicon super surface is simple and the cost is low. Compared with the super-surface of a multilayer metal frame, the full-silicon super-surface does not need a cumbersome process. However, in the terahertz waveband, the interaction between silicon materials and terahertz is weak, and good circular dichroism is generally difficult to form, so that at present, few researches are made on devices based on spin-selective transmission of the all-silicon super-surface, and the circular dichroism of the spin-selective transmission all-silicon super-surface reported in the existing literature is only 0.3 at most.

Disclosure of Invention

The present invention is directed to provide a design method of a terahertz spin selective transfer all-silicon super-structure device to solve or improve the above-mentioned problems.

In order to achieve the purpose, the invention adopts the technical scheme that:

a design method of a terahertz spin selective transmission all-silicon super-structure device comprises the following steps:

s1, constructing a basic structure based on the all-silicon lossy material, wherein the basic structure comprises three geometrically distributed elliptical strips;

and S2, periodically extending the basic structure in the S1 to form a super surface.

Further, all silicon is high resistance silicon.

Furthermore, two of the three elliptical strips have the same size, and the two elliptical strips with the same size are arranged in pairs and form an inclined included angle of 45 degrees with the third elliptical strip; the major axis of the third elliptical strip is the same as the major axes of the other two elliptical strips, and the minor axes are different.

The design method of the terahertz spin selective transmission all-silicon super-structure device provided by the invention has the following beneficial effects:

the invention strengthens the interaction between the terahertz wave and the silicon, designs the spin selective transmission all-silicon super-surface, obtains excellent spin selective transmission characteristic in the terahertz wave band, has circular dichroism reaching 0.4, and improves the circular dichroism of the spin selective transmission all-silicon super-surface by about 30 percent compared with the existing report.

Besides, the invention does not depend on the traditional composite full-medium system and multilayer metal system, realizes high-performance terahertz spin selective transmission on the full-silicon material through ingenious structural design, and has the advantages of simpler preparation process, easy batch production, high yield and small product error.

Compared with the existing similar products, the circular dichroism reported by the invention is improved by more than 30 percent, which means stronger spin selective transmission characteristics.

Drawings

Fig. 1 is a schematic two-and three-dimensional view of the basic structure.

FIG. 2 is a functional diagram of a super-structure device formed by periodically extending basic structures.

FIG. 3 is a graph of the performance characteristics of a nanostructured device in which (a) the transmission amplitude of the different circular polarization components and (b) the circular dichroism curve.

Detailed Description

The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.

In a first embodiment, referring to fig. 1, the method for designing a terahertz spin selective transmission all-silicon super-structure device in the present scheme includes the following steps:

s1, designing a basic structure based on the all-silicon lossy material, wherein the basic structure is formed by arranging three elliptical strips according to a certain geometric rule.

And S2, periodically extending the basic structure designed in the step one to form a super surface.

The above designs are all based on high resistance silicon.

The total thickness of the silicon is 500 μm, the structure depth is 200 μm, and the period constant of the basic structure in the first step is 160 μm; two of the three elliptical strips have the same size, the major axis is 90-100 μm, the minor axis is 20-25 μm, and the major axis of the third elliptical strip is 90-100 μm, but the minor axis is 50-60 μm. Two elliptical strips of the same size were arranged in pairs with a center distance of 80 μm and a 45 ° oblique angle to the third elliptical strip. If the center of the whole structure is taken as the origin of coordinates, the center coordinates of two elliptical strips with the same size are (40, 40) and (40, -40); the center of the third strip was spaced 80 μm from the overall geometric center of the other pair of strips with center coordinates (-40, 0). The central operating band of the device of the invention is 1.05 THz.

The present invention will be described in detail with reference to examples.

Example two

S1, designing a basic structure based on the all-silicon lossy material, wherein the basic structure consists of three elliptical strips. As shown in fig. 1, the selected silicon material is high-resistance silicon. The total thickness of silicon is 500 μm, where the substrate portion thickness h2 ═ 300 μm, the structure depth h1 ═ 200 μm, and the structure period constant P ═ 160 μm; two of the three elliptical strips have the same size, the major axis is L (100 μm), the minor axis is W2 (20 μm), the major axis is L (100 μm), and the minor axis is W1 (60 μm). Two elliptical strips of the same size are arranged in pairs, are centered at a distance of 80 μm and are inclined at an angle θ of 45 ° to the third elliptical strip. If the center of the whole structure is taken as the origin of coordinates, the center coordinates of two elliptical strips with the same size are (40, 40) and (40, -40); the third ellipse bar has a major axis parallel to the y axis of the coordinate and a minor axis parallel to the x axis of the coordinate, with its center coordinate (-40, 0).

And S2, periodically extending the basic structure designed in the step one to form a super surface. As shown in fig. 2, the central operating band of the device of the present invention is 1.05 THz. The functions provided are described as follows: when right-handed circularly polarized (RCP) terahertz waves are incident from the front of the device, they are transmitted smoothly and are converted into left-handed circularly polarized (LCP) terahertz waves, which, however, are reflected and cannot be transmitted smoothly when they are incident from the front of the device. The transmission amplitude of each circularly polarized component is shown in fig. 3(a), and its circular dichroism is shown in fig. 3 (b); it can be seen that the circular dichroism of the device is as high as 0.4 at 1.05THz, a value which is at least 30% higher than that reported previously.

In conclusion, the invention realizes high-performance terahertz spin selective transmission on the all-silicon material through ingenious structural design without depending on the traditional composite all-dielectric system and multilayer metal system, obtains the circular dichroism value as high as 0.4, and is improved by at least 30% compared with the existing record. The device of the invention has simpler preparation process, easy batch production, high yield and small product error.

While the embodiments of the invention have been described in detail in connection with the accompanying drawings, it is not intended to limit the scope of the invention. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.