Narrowband-to-broadband switchable and polarization-insensitive terahertz metasurface absorber enabled by phase-change material

Abstract

A terahertz absorber with controllable and switchable bandwidth and insensitive to polarization is of great interest. Here, we propose and demonstrate a metasurface absorber with switchable bandwidth based on a phase-change material of vanadium dioxide (VO2) and verify its performance by the finite element method simulations. The metasurface absorber is composed of a hybrid cross fractal as a resonator separated from a gold ground-plane by a polyimide spacer. Switching from narrowband to broadband absorber is achieved via connecting VO2 patches to the gold first-order cross fractal converting the resonator to a third-order cross fractal. In the insulator phase of VO2, the main narrowband absorption occurs at the frequency of 6.05 THz with a 0.99 absorption and a full-width half-maximum (FWHM) of 0.35 THz. Upon insulator-to-metal transition of VO2, the metasurface achieves a broadband absorption with the FWHM of 6.17 THz. The simulations indicate that by controlling the partial phase-transition of VO2, we can tune the bandwidth and absorption level of the absorber. Moreover, the designed absorber is insensitive to polarization due to symmetry and works well for a very wide range of incident angles. In the metallic state of VO2, the absorber has an absorption exceeding 0.5 in the 3.57-8.45 THz frequency range with incident angles up to 65°.

Superresolution in phase image of π-phase step on plasmonic metasurface using differential heterodyne microscope

“…There are many techniques to create phase objects. Recently, the study of phase objects based on plasmonic metasurfaces has become widespread, including for various applications in optical radiation control systems and elements, such as terahertz absorbers, nonlinear integrated optics, thermal emission control, and focusing elements 31 – 38 The question arises whether it is possible to use this promising technology to fabricate phase objects suitable for observing the superresolution effect in edge detection.…”

“…Recently, the study of phase objects based on plasmonic metasurfaces has become widespread, including for various applications in optical radiation control systems and elements, such as terahertz absorbers, nonlinear integrated optics, thermal emission control, and focusing elements. [31][32][33][34][35][36][37][38] The question arises whether it is possible to use this promising technology to fabricate phase objects suitable for observing the superresolution effect in edge detection. The answer on this question is not obvious, since the characteristic size of the unit cell of the metasurface [35][36][37] is comparable with the wavelength of optical radiation and with the size of the focused probing spot of the microscope.…”

Fabric‐Based Smart Metasurface

“…[34] A key challenge when using fabric as the substrate for tunable metasurfaces lies in the contradiction between the bad hightemperature resistance of fabric material and the need of welding a large number of semiconductor components (PIN diodes and varactors). Although various approaches have been attempted to realize active function by combining the passive meta-structure with new materials including phase change materials, [35,36] 2D materials (i.e. graphene and MoS2), [10,17,26,[37][38][39] and liquid crystals, [40] the way of integrating Si-based components are still necessary because of more consistent performance and faster response speed.…”

TiN-GST-TiN all-optical reflection modulator for the 2 µm wave band reaching 85% efficiency

“…In recent years, due to unique combination of optical properties upon phase change [23][24], many phase change materials such as Sb 2 S 3 [25], Sb 2 Se 3 [26], Ge 2 Sb 2 Se 4 Te 1 (GSST) [27], Ge 2 Sb 2 Te 5 (GST) [28] and VO 2 [29] have drawn more attention in the fields of optical absorption [30], modulation [31], filtration [32] and micro-display [26]. Though VO 2 shows discernible metal-to-insulator phase transition, it is volatile.…”