Vanadium Dioxide Integrated Metasurfaces with Switchable Functionalities at Terahertz Frequencies

Abstract

fabrication, while enabling an unprecedented control over optical fields. [1][2][3][4][5] In contrast to the conventional methods for molding the EM wave propagation that strongly depend on the gradually accumulated phase during wave propagation, the metasurface operation is based on local modifications of the boundary conditions for impinging waves. Metasurface configurations are thereby fundamentally different from conventional optical components usually featuring curved and spatially extended (i.e., bulky) shapes and forms. Thus the resulting metadevices are surface-confined within subwavelength thicknesses, opening exciting possibilities for very dense integration and miniaturization in photonics. As such, a variety of unique phenomena and fascinating applications have been demonstrated by designed metasurfaces, including beam-steering, [6][7][8][9][10][11] surface waves couplers, [12][13][14][15] focusing lenses, [16][17][18][19] optical holograms, [20][21][22][23] broadband absorbers, [24][25][26][27][28][29] waveplates, [30][31][32][33][34][35][36][37] and polarimeters. [38][39][40] Up to now, most of the metasurfaces have been typically designed for a single functionality. Even though there have been reported various polarization-controlled metasurfaces, [10,[13][14][15]20] they process similar or identical functionalities. In this way, metasurfaces that facilitate effective integration of multiple diversified functionalities into one single device have become an emerging research area, especially interesting for terahertz (THz) range. Very recently, polarization coding has been proposed to realize multifunctional metasurfaces for circularly polarized [39,41] and linearly polarized light. [42,43] However, the implemented approach suffers from intrinsic crosstalk between different polarizations, and the efficiency of each functionality is inevitably limited due to its polarization-sensitive nature. To realize diversified functionalities, an alternative way is to hybridize metasurfaces with active functional materials, such as phase-change materials (PCM). [44][45][46][47][48][49][50][51][52][53][54][55] While PCM integrated metasurfaces have been successfully demonstrated to achieve the active configuration control, metasurfaces processing multiple distinct functionalities over a wide wavelength/frequency range still remain largely unexplored.In this paper, we design operating at THz frequencies polarization insensitive and tunable metasurfaces with diversified functionalities based on vanadium dioxide (VO 2 ), which undergoes the insulator-to-metal transition. Our simulations Integration of switchable and diversified functionalities into a single metasurface has become an emerging research area that requires dealing with formidable challenges, especially for terahertz (THz) frequencies. Here, polarization-insensitive and switchable THz metasurfaces are proposed with diversified functionalities that exploit insulator-to-metal transition in vanadium dioxide (VO 2 ). The simulations demonstrate that the desi...

Reprogrammable multifocal THz metalens based on metal–insulator transition of VO2-assisted digital metasurface

“…When VO2 passes the transition temperature, it comes to the metallic state. In this case, relative permittivity is constant, but the conductivity increases as high as an order of 10 5 [39].…”

Dynamic Terahertz Plasmonics Enabled by Phase‐Change Materials

“…[76,81,[86][87][88][89][90][91][92][93][94][95][96][97][98][99] The early demonstration of a THz metamaterial made of VO 2 involved an array of cut-wire-type resonators without any metal structures (Figure 7a). Instead of thin films, small pieces of VO 2 are integrated into metamaterial designs as a part of resonators so that the resonance properties can be directly tuned by controlling the IMT.…”

Multifunctional linear‐polarized terahertz focusing metasurface

“…Multifunctional devices have been realized by recently proposed metasurfaces combined with tunable two‐dimensional material at terahertz frequencies, such as vanadium dioxide (VO 2 ), graphene . In 2018, Bozhevolnyi et al proposed polarization‐insensitive and switchable THz metasurfaces with diversified functionalities that exploit insulator‐to‐metal transition in VO 2 . In 2019, a broadband active meta‐holography composed of vanadium dioxide (VO 2 ) integrated CSRRs, which enables temperature‐dependent dynamic holographic imaging was experimentally demonstrated by Zhang et al In addition to metal structures nested with two‐dimensional materials, metasurfaces based on metal and dielectric structure achieving multifunctionality work mainly either in reflection mode, or circular polarization mode incidence .…”