CN-116780203-B - Terahertz beam splitter with adjustable beam splitting ratio and manufacturing process thereof

CN116780203BCN 116780203 BCN116780203 BCN 116780203BCN-116780203-B

Abstract

The invention discloses a terahertz beam splitter with an adjustable beam splitting ratio, which is formed by arranging super units in a arrayed mode, wherein the super units are formed by 8 or 8 basic units, 4 basic units are symmetrically distributed according to a phase difference, each basic unit comprises a dielectric layer, an opening circular ring type metal pattern layer and a metal reflecting layer, the opening circular ring type metal pattern layer is positioned on the dielectric layer, the metal reflecting layer is positioned below the dielectric layer, the metal reflecting layer covers half of the dielectric layer, the metal reflecting layer only covers the basic units positioned on the left side of a symmetry axis, the phase difference between the 4 basic units of the super surface beam splitter is 90 degrees when terahertz waves vertically enter in the direction of a-z axis, a quarter beam is obtained when the terahertz waves vertically enter in the direction of the-z axis through observing far field patterns in simulation software, the beam splitting ratio is 1.2:1, and the quarter beam is obtained when the terahertz waves vertically enter in the direction of the +z axis through observing the far field patterns in the simulation software, and the beam splitting ratio is 1.9:1.

Inventors

PAN WU
ZHU ZIHENG
HU SHENGJIAN
TAN MINGSEN
CHEN XIN
XU YINGSONG
SHENG HONGYUAN

Assignees

重庆邮电大学

Dates

Publication Date: 20260512
Application Date: 20230406

Claims (8)

1. A terahertz beam splitter with an adjustable beam splitting ratio is characterized by being formed by arranging super units in a arrayed mode, wherein each super unit comprises 8 base units and an opening circular ring type metal pattern layer, each base unit comprises a medium layer and the opening circular ring type metal pattern layer, the opening circular ring type metal pattern layer is located above the medium layer, 4 base units are formed by changing the inner diameter and the opening size of the opening circular ring type metal pattern, the phase difference between the 4 base units of the super surface beam splitter is 90 degrees when the phase difference is 0.7THz, the super units are symmetrically arranged left and right, the 4 base units are symmetrically arranged on two sides of a symmetry axis according to the phase difference, a metal reflection layer is located below the medium layer, the metal reflection layer covers half of the medium layer of the super units, the metal reflection layer covers the base units located on the left of the symmetry axis, when terahertz waves are vertically incident in the direction of-z axis, four-beam splitting is obtained when the terahertz waves are vertically incident in the direction of 0.7:1 through observing far field diagrams in simulation software, and the beam splitting ratio is obtained when the terahertz waves are vertically incident in the direction of +z direction, and the four-beam splitting ratio is 0.539:1 when the terahertz waves are obtained when the far field diagrams in the simulation software are observed in the direction of 0.7:5.
2. The adjustable beam splitting ratio terahertz beam splitter of claim 1, wherein the dielectric layer of the base unit is polyimide, has a dielectric constant of 3.5, a thickness d=50 μm, and a dimension p=125 μm×125 μm.
3. The adjustable beam splitting ratio terahertz beam splitter of claim 1, wherein the metal pattern layer is made of gold, has a thickness of 0.2 μm, and has an electrical conductivity of 4.561 x10 7 S/m.
4. The terahertz beam splitter according to claim 1, wherein the metal reflective layer is made of gold, has a thickness of 0.2 μm, and has an electrical conductivity of 4.561 x10 7 S/m.
5. The terahertz beam splitter according to claim 1, wherein the specific dimensions of the metal pattern layer of one base unit are respectively an open circular ring inner diameter h 1 = 57.5 μm, a circular ring opening size g = 10.0 μm, a dielectric layer thickness d = 50.0 μm, the remaining base units are constructed by changing h 1 , g, the open circular ring inner diameters of the remaining 3 base units are respectively 52.0 μm, 30.0 μm, 43.75 μm, and the circular ring opening sizes are respectively 10.0 μm, 25.0 μm, 10.0 μm.
6. The adjustable beam splitting ratio terahertz beam splitter of claim 1, wherein the Generalized stoneley reflection theorem for beam splitters The generalized stoneley refraction theorem for beam splitters is , wherein, And Representing the angle of reflection and the angle of incidence, And The refractive index of the incident medium and the outgoing medium is represented, lambda 0 represents the wavelength of the incident wave, and the phase change gradient dΦ/dx at the interface.
7. The adjustable beam splitting ratio terahertz beam splitter according to claim 1, wherein the basic unit period of the super surface beam splitter is 120 μm by 120 μm to 130 μm by 130 μm, and the above 4 kinds of open annular basic unit parameters are realized by changing the inner diameter of the annular ring to 20-60 μm and the opening size of the annular ring to 10-50 μm.
8. A process for manufacturing a terahertz beam splitter with an adjustable beam splitting ratio according to any one of claims 1 to 7, comprising the following steps: The method comprises the steps of designing 4 basic unit structures and arranging the basic unit structures into super units, wherein a metal pattern layer adopts a classical anisotropic open circular ring structure, so that a phase difference condition meeting 90 degrees can be generated in the x-axis direction when terahertz waves are incident, and no phase difference exists in the y-axis direction; Cleaning the photoetching mask plate, namely putting the photoetching mask plate into an ultrasonic cleaner containing acetone to clean, removing surface impurities, then putting the photoetching mask plate into absolute ethyl alcohol to soak, cleaning the mask plate by using deionized water, and finally drying by using a nitrogen gun; step three, cleaning the polyimide substrate by using acetone and alcohol in advance, and keeping the polyimide surface of the substrate dry; Plating gold with thickness of 200nm and titanium with thickness of 10nm on two sides of the polyimide film by utilizing a magnetron sputtering machine FHR, wherein the titanium is added for increasing the adhesiveness between the metal and the polyimide; Step five, gluing and pre-drying, namely placing the sample on a glue homogenizing machine for glue homogenizing, and then pre-drying the glued sample; exposing and developing, namely exposing and photoetching the sample by using a photoetching machine, and then developing the sample by using a developing solution; Etching the top layer and the bottom layer of the super surface metal by using an ion beam etching machine; and step eight, photoresist removing, namely placing the etched sample into an acetone solution for soaking, then removing a photoetching machine on the surface of the sample by using a plasma photoresist remover, and finally cleaning the sample by using deionized water and air-drying.

Description

Terahertz beam splitter with adjustable beam splitting ratio and manufacturing process thereof Technical Field The invention belongs to the technology of terahertz beam splitters, in particular to a terahertz beam splitter with an adjustable beam splitting ratio and a manufacturing process thereof. Background Terahertz (Terahertz, THz) waves refer to electromagnetic waves with a frequency range of 0.1-10 THz. The long wave band of terahertz is coincident with microwaves, the short wave band is coincident with infrared waves, and compared with electromagnetic waves of other wave bands, the terahertz has wide application prospect in the fields of biomedicine, nondestructive detection, communication application and the like due to the position specificity. The two-dimensional equivalent of the super surface as the metamaterial is a periodic sub-wavelength artificial electromagnetic medium, and has wide application on terahertz beam splitter devices due to the negative refractive index, electromagnetic induction-like transparent effect, nonlinear effect and the like. In 2017, s.l.l. Wendy et al proposed an ultrathin circularly polarized terahertz beam splitter, whose super surface unit is a coaxial split ring resonator, and when a circularly polarized wave is perpendicularly incident, the reflected wave is split into two beams of a left-handed circularly polarized wave and a right-handed circularly polarized wave, and the two beams of the circularly polarized wave are split at a splitting ratio of 1:1 when 0.58-1.00 thz. 2022, zhang Changchang et al propose a periodic metal surface composed of a single layer copper structure, which can realize two beam splitting of terahertz waves at 0.8-1.1 thz, and the beam splitting ratio of the beam splitter is 1:1. With the research of beam splitters, the beam splitter with single beam splitting ratio cannot meet many application scenes, so the research direction gradually develops to the beam splitter with tunable beam splitting ratio. In 2022, yin S et al designed an active terahertz beam splitter device based on an open circular array, and the beam splitting ratio of y-polarized waves was controlled by controlling the reflection and absorption of terahertz waves by the super-surface array by using pump light to illuminate the super-surface array, and the beam splitting ratio could be varied from 1:1 to 15:1. The terahertz beam splitter achieves a good beam splitting effect, but only achieves a single beam splitting ratio, and once the beam splitting ratio is manufactured, the beam splitter is fixed, and the beam splitting ratio is tunable, so that the terahertz beam splitter is an active device, has high cost, and limits the application of the terahertz beam splitter in aspects of multi-signal transmission, imaging, stealth and the like of the terahertz communication. CN 201910348908.4A terahertz metamaterial beam splitter has a unit structure composed of a top metal strip, a middle dielectric layer and a bottom metal plate. The periodic arrangement forms a 4 x 4 phase gradient subsurface using 4 units with a rotational step of 45 °. When terahertz waves are perpendicularly incident on the array surface, electromagnetic waves are reflected into four waves of equal energy but different propagation directions, and reflection angles of different frequency points are different. The beam splitter has the advantages of small volume and low cost, and can be applied to the aspects of terahertz stealth, terahertz imaging and the like First, the ratio of the incident electromagnetic wave beam is 1:1, and the ratio of the electromagnetic wave beam split when the electromagnetic wave enters the direction of the-z axis is 1.2:1, the ratio of the electromagnetic wave beam split when the electromagnetic wave enters the direction of the +z axis is 1.9:1, and the energy of the beam split generated when the electromagnetic wave enters is not equal. Secondly, the patent is a passive device, the beam splitting ratio of the passive device cannot be changed after the passive device is manufactured, the structure proposed herein is the passive device, but different beam splitting ratios can be generated by incident electromagnetic waves in different directions, and two different beam splitting ratios can be realized herein. Disclosure of Invention The present invention is directed to solving the above problems of the prior art. A terahertz beam splitter with adjustable beam splitting ratio and its manufacture are disclosed. The technical scheme of the invention is as follows: The terahertz beam splitter with the adjustable beam splitting ratio is formed by arranging super units in a arrayed mode, the super units are formed by 8 x 8 base units, 4 base units are symmetrically arranged according to a phase difference, 4 base units are formed by changing the inner diameter and the opening size of an opening circular ring type metal pattern, each base unit comprises a dielectric layer, an opening