Terahertz Chirality Response Of Flexible Metamaterials

Terahertz(THz)wave has the excellent electronics and the photonics properties,it has great application prospects in many important fields such as radar,remote sensing,highsecurity data communication and transmission,atmospheric and environmental monitoring,real-time biological information extraction and medical diagnosis have gradually emerged.The limitation of the development of THz technology is primarily a result of the lack of the naturally occurring materials which support strong terahertz(THz)wave-matter interaction.Therefore,metamaterials and metasurfaces which structures are constructed by artificial design have attracted the attention of related researchers in the field of THz technology since they exhibit great flexibility to electromagnetic properties.In terahertz wave manipulation,the manipulation of polarization is a hot research topic.Therefore,chiral metamaterials,chiral metasurfaces,and terahertz polarization components attracted the attention of many researchers.The previous chiral metamaterials and chiral metasurfaces usually have the disadvantages of high production difficulty and high cost,and they are difficult to be applied to micro devices.Therefore,easy-to-fabricate,large-area,and inexpensive microstructures that realize control of the polarization of terahertz(THz)radiation are of fundamental importance to the development of the field of THz wave photonics.In this paper,we design a chiral functional device based on textile technology and a dual-band spin-selective flip chiral reflective metamirror,which not only have great polarization manipulation ability,but also have the advantages of simple structure,low cost and good application prospect.The main research contents are as follows:(1)A terahertz chiral functional device based on textile technology is designed,which consists of leveraging a two-step textile manufacturing approach microhelical strings on optical fibers into an array.The CST microwave studio is used to study the influence of the loss tangent value of the selected optical fiber,the diameter of the optical fiber,the diameter of the copper wire,the distance between the copper helix and the distance between the optical fiber on the working frequency and the amplitude of the chiral response of the designed structure.The fabricated sample by appropriate parameters is tested and analyzed.The results show that the chiral metamaterial have a strong chirality response at terahertz frequency,which verifies that the chiral selective transmission and polarization manipulation effects can be realized by the change of material parameters and fabrication parameters in a simple micro-helical textile structure.It also provides a proof of concept for the application of textile technology-based microstructures in terahertz components with complex functions.(2)In this work,we have demonstrated a flexible flip chiral dual-band THz reflective metamirror which has the ability to realize opposite spin selection reflection in two different frequency bands.The design of this metamirror is based on a typical chiral structure,which consisting of two asymmetric C-shaped structures.We can adjust the lengths and heights of part of the structure to modulate the value of chiral response and change the frequency that chiral response occurred.The metamirror is fabricated using standard UV lithography,we measure four linear reflection coefficients to exhibition the circular reflection coefficients by using Terahertz time-domain spectroscopy(THz-TDs).Comparing the spectra of simulation and experiment,the experimental results are in good agreement with the simulation results,indicating that the metasurface designed by us has good selective reflection and flip chirality.The metasurface essentially realizes the dual-band manipulation of THz spin wave.