Dynamically tunable single-layer VO₂/metasurface based THz cross-polarization converter

Abstract

We demonstrate a single-layer THz metadevice that exhibits cross polarization transmission, a key factor to achieve optical activity. The device is comprised of a two-dimensional array of split ring resonators, each with a vanadium oxide (VO2) pad, integrated into one of the two capacitive gaps of the unit cell. Through numerical investigations we find that as the conductivity of VO2 increases the amplitude of the cross-polarization intensity decreases but maintains a wider broadband range than previously reported for single layered hybrid metamaterial (MM) devices as the VO2 transforms from the insulator to metallic phase. Also the asymmetric transmission, optically modulated by the device, is higher than that of multi-layered MM devices. Due to the materials properties of VO2, our results introduce a promising method that allows for an active sub-cycle dynamic tunability for THz polarization conversion with multiple modalities using optical, electrical or thermal switching. The study is an important step forward in developing compact, integrated, passive and active metadevices for polarization and wavefront control application in the THz.

A Review: The Functional Materials-Assisted Terahertz Metamaterial Absorbers and Polarization Converters

“…Dynamical reconfigurable and switchable metamaterial structures based on phase change materials exhibit a controllable degree of freedom in the application of light-matter interaction and information processing [119]. Phase change materials, including GST [120][121][122][123][124], GeTe [125][126][127], VO 2 and so on, can be used to dynamically manipulate the metamaterial structures since the different optical and electronic characteristics of these materials can be achieved by changing their structural phases through a variety of external stimulation.…”

“…When VO2 film is in metal state, the ellipticity of the LTC converter is close to -1, while the axis ratio is lower than 3 dB in the range of 1.07-1.67 THz. Due to the dielectric properties of the VO 2 with insulating state, transmission function combined with other functions can also be realized [119,[157][158][159]. In Figure 15a, L. L. Chen et al introduced VO 2 film into a multi-layer design to achieve the dual-function of absorption and high transmission [157].…”

Terahertz MEMS metadevices

“…These active materials can be incorporated into the metamaterial as the substrate, surrounding media, part of the resonator or as an entire resonator itself. Various material systems have been explored for THz metadevices, including conventional semiconductors [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], phase change materials [38][39][40][41], phase transition materials [42][43][44][45][46][47][48], liquid crystals [49][50][51][52][53], 2D materials [54][55][56][57][58][59][60][61][62][63][64][65], 3D semimetals [66], topological insulators [67], perovskites [68]…”

Terahertz bandstop-to-bandpass converter based on VO2 hybrid metasurface

“…Metasurface is an artificial surface composed of some periodic sub-wavelength arrays and has unique EM properties that are not available in natural materials [3,4], and thus it can provide a way for the design of THz functional devices. Recently, many devices based on the metasurface have been demonstrated, such as THz coder [5], polarization converter [6], active quarter-wave-plate [7], wavefront modulators [8], multifunctional device [9,10] and absorbers [11][12][13][14].…”