CN108279515B

CN108279515B - Metamaterial wave absorber based on liquid crystal

Info

Publication number: CN108279515B
Application number: CN201810353921.4A
Authority: CN
Inventors: 邓光晟; 赵天翔; 卢玉娇; 杨军; 尹治平
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2018-04-19
Filing date: 2018-04-19
Publication date: 2021-05-04
Anticipated expiration: 2038-04-19
Also published as: CN108279515A

Abstract

The invention discloses a metamaterial wave absorber based on liquid crystal, which comprises a plurality of wave absorbing units which are continuously arranged, wherein each wave absorbing unit comprises an upper layer of medium substrate and a lower layer of medium substrate, a liquid crystal layer is injected into a gap between the upper layer of medium substrate and the lower layer of medium substrate, a metal resonance unit is arranged on the lower surface of the upper layer of medium substrate, the metal resonance unit consists of a metal ring with four crossed symmetrical openings and four crossed symmetrical metal wires connected with the metal ring, and a metal layer is fully covered on the upper surface of the lower layer of medium substrate to form a metal grounding electrode. The adjusting width of the absorption frequency of the invention can reach 6.19 percent, and the adjusting range is large; the absorption rate under large-angle incident waves is high, the absorption rate of the invention for incident waves with different polarizations can still be maintained above 88% when the incident angle of the incident waves reaches 60 degrees, and the stability of absorption frequency is high.

Description

Metamaterial wave absorber based on liquid crystal

Technical Field

The invention relates to the technical field of metamaterials, in particular to a metamaterial wave absorber based on liquid crystal.

Background

The metamaterial is a novel artificial structural material, has supernormal electromagnetic characteristics which are not possessed by natural materials, and provides a new way for controlling electromagnetic waves. The metamaterial wave absorber is an important application field of the metamaterial and has attracted extensive attention of researchers in various countries around the world. The absorption frequency of the traditional metamaterial wave absorber is generally a fixed value and is difficult to change after processing. In recent years, researchers have made a lot of research in the direction of frequency tunable metamaterial absorbers, and materials such as graphene and vanadium dioxide are used to adjust the absorption frequency, and materials such as liquid crystal having a birefringence effect are also used in the design of frequency tunable metamaterial absorbers. However, the main problem of the existing frequency-adjustable metamaterial wave absorber is that the absorption rate under large-angle incident waves is very low, so that the practical application of the device is greatly limited.

Disclosure of Invention

The invention aims to make up the defects of the prior art and provides a metamaterial wave absorber based on liquid crystal.

The invention is realized by the following technical scheme:

the utility model provides a metamaterial wave absorber based on liquid crystal, is including a plurality of wave absorbing units that set up in succession, every wave absorbing unit including upper and lower two-layer medium base plate's clearance in inject into and have the liquid crystal layer upper medium base plate lower surface be equipped with the metal resonance unit, the metal resonance unit by one have four cross symmetry open-ended becket and connect four cross symmetrical metal cords of becket lower floor's medium base plate upper surface cover one deck metal level entirely, form metal earthing electrode.

The liquid crystal layer adopts nematic liquid crystal materials.

By applying a voltage to the metal resonance unit and the metal ground electrode, a bias electric field is formed in the liquid crystal layer.

By applying voltage on the metal resonance unit and the metal grounding electrode, a bias electric field is formed in the liquid crystal layer, and the bias electric field enables the arrangement direction of liquid crystal molecules to deflect, so that the dielectric constant of the liquid crystal is changed, and the absorption frequency of the wave absorber is further changed.

The invention has the advantages that: the adjusting width of the absorption frequency of the invention can reach 6.19 percent, and the adjusting range is large; the absorption rate under large-angle incident waves is high, the absorption rate of the invention for incident waves with different polarizations can still be maintained above 88% when the incident angle of the incident waves reaches 60 degrees, and the stability of absorption frequency is high.

Drawings

Fig. 1 is a schematic three-dimensional structure diagram of the wave absorbing unit of the invention.

Fig. 2 is a front view of the structure of the wave absorbing unit in the invention.

FIG. 3 is a schematic view of a metal resonant unit structure on the lower surface of the upper dielectric substrate according to the present invention.

FIG. 4 is a graph showing the simulation results of the absorption rate at normal incidence under different liquid crystal dielectric constants.

FIG. 5 is a graph showing the results of absorption rate simulation for a wide incident angle of TE polarized waves when the liquid crystal dielectric constant is 2.47 according to the present invention.

Fig. 6 is a graph showing the results of absorption rate simulation in the case of a wide incident angle of TM polarized wave when the liquid crystal dielectric constant is 2.47 according to the present invention.

Detailed Description

As shown in fig. 1, 2 and 3, a metamaterial wave absorber based on liquid crystal comprises a plurality of wave absorbing units which are continuously arranged, each wave absorbing unit comprises an upper layer of medium substrate 1 and a lower layer of medium substrate 2, a liquid crystal layer 3 is injected into a gap between the upper layer of medium substrate 1 and the lower layer of medium substrate 2, a metal resonance unit 4 is arranged on the lower surface of the upper layer of medium substrate 1, the metal resonance unit 4 is composed of a metal ring 6 with four crossed symmetrical openings and four crossed symmetrical metal wires 7 connected with the metal ring, and a metal layer 5 is fully covered on the upper surface of the lower layer of medium substrate 2 to form a metal grounding electrode.

The liquid crystal layer 3 adopts nematic liquid crystal material.

By applying voltage to the metal resonance unit 4 and the metal grounding electrode, a bias electric field is formed in the liquid crystal layer, and the bias electric field deflects the arrangement direction of liquid crystal molecules, so that the dielectric constant of the liquid crystal is changed, and the absorption frequency of the wave absorber is further changed.

In the specific implementation process, the corresponding structural arrangement comprises:

the upper dielectric substrate 1 has a side length of a and a thickness of H_qThe lower dielectric substrate 2 has a side length of a and a thickness of H_qThe cubic structure of (1).

The metal resonance unit 4 comprises a metal ring, the inner and outer diameters of which are R and R, and the metal ring has four openings with width w and cross symmetry. The metal loops of each adjacent cell are connected by a metal line of width s. The thickness of the metal resonance unit is t.

The upper surface of the lower dielectric substrate 2 is fully covered with a metal layer 5 with the thickness t as a metal grounding electrode.

In one embodiment, the liquid crystal layer has a thickness of H_LCAfter filling the liquid crystal material into the gap between the medium substrates, sealing with epoxy resin, and filling the liquid crystal material into the gapThe upper and lower surfaces of the layer are oriented with polyimide films.

In a specific application, the following are set:

size of cell a =400 μm, size of metal resonance cell: r =165 μm, R =115 μm, w =20 μm, s =20 μm. The thickness of the liquid crystal layer is 43 mu m, the thickness of the upper dielectric substrate and the thickness of the lower dielectric substrate are both 400 mu m, and the thickness of the metal resonance unit and the thickness of the metal layer are both 0.5 mu m. The liquid crystal material in the liquid crystal layer is S200, and the metal grounding electrode and the metal resonance unit are made of metal copper. The dielectric substrate is made of quartz material, the dielectric constant is 3.78, and the loss tangent is 0.02.

Fig. 4 is a vertical incidence absorption rate curve of the wave absorber obtained by software simulation under different liquid crystal dielectric constants, and the absorption frequency of the wave absorber changes along with the change of the liquid crystal dielectric constant. When the dielectric constant of the liquid crystal is changed from 2.47 to 3.06, the absorption frequency is changed from 194.24GHz to 182.01GHz, and the adjustment width of the absorption frequency of the wave absorber can reach 6.19%.

Fig. 5 and 6 are absorption curves of the present invention at wide incident angles of TE polarized waves and TM polarized waves when the liquid crystal dielectric constant is 2.47, respectively. It can be seen from the figure that, no matter the wave is TE polarized wave or TM polarized wave, when the incident angle reaches 60 degrees, the absorption rate of the wave absorber to the incident wave can still be kept above 88%, and the stability of the absorption frequency is high.

Claims

1. A metamaterial wave absorber based on liquid crystal is characterized in that: the wave absorbing device comprises a plurality of wave absorbing units which are continuously arranged, wherein each wave absorbing unit comprises an upper dielectric substrate and a lower dielectric substrate, a liquid crystal layer is injected into a gap between the upper dielectric substrate and the lower dielectric substrate, a metal resonance unit is arranged on the lower surface of the upper dielectric substrate, the metal resonance unit consists of a metal ring with four crossed symmetrical openings and four crossed symmetrical metal wires connected with the metal ring, and a metal layer is fully covered on the upper surface of the lower dielectric substrate to form a metal grounding electrode;

the liquid crystal layer adopts nematic liquid crystal material;