Abstract-Temperature-controlled terahertz polarization conversion bandwidth

 

Jing Zhao, Chunmei Ouyang, Xieyu Chen, Yanfeng Li, Caihong Zhang, Longcheng Feng, Biaobing Jin, Jiajun Ma, Yi Liu, Shoujun Zhang, Quan Xu, Jiaguang Han,  Weili Zhang, 

Schematic diagram of the metasurface structure and experimental system. (a) Unit cell, composed of sapphire substrate, VO2 and gold SRRs layers, polyimide dielectric layer and a gold grating, with geometrical parameters h = 2000 µm, P = 80 µm, d = 200 nm, t = 35 µm, d1 = 10 µm, and d2 = 22 µm. (b) Vertical view of the unit cell. (c) Gold SRR with geometrical parameters O = 10°, O1 = 10°, C1 = 30°, and C2 = 45°. (d)-(f) Optical microscope images of the fabricated VO2 and gold SRRs, gold grating and their combined structure, respectively. (g) Sample characterization by THz-TDS.

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Active control of metasurfaces has attracted widespread attention because of the adjustable electromagnetic properties obtained. Here we designed and experimentally studied a dynamically controllable polarization converter in the terahertz band. By designing the structural parameters and utilizing the insulator-to-metal phase transition of vanadium dioxide and principle of current resonance, dynamic tunability of the polarization conversion function from dual-broadband (0.45∼0.77 THz and 0.97∼1.2 THz) to ultra-broadband (0.38∼1.20 THz) can be realized with a high polarization conversion ratio. The scheme proposed here can find potential applications in integrated terahertz systems, sensing, imaging and communications areas.

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