Wideband switchable dual-functional terahertz polarization converter based on vanadium dioxide-assisted metasurface
Dexian Yan, Qinyin Feng, Ziwei Yuan, Miao Meng, Xiangjun Li, Guohua Qiu, Jining Li
Abstract
The terahertz technology has attracted considerable attention because of its potential applications in various fields. However, the research of functional devices, including polarization converters, remains a major demand for practical applications. In this work, a reflective dual-functional terahertz metadevice is presented, which combines two different polarization conversions through using a switchable metasurface. Different functions can be achieved because of the insulator-to-metal transition of vanadium dioxide (VO 2 ). At room temperature, the metadevice can be regarded as a linear-to-linear polarization convertor containing a gold circular split-ring resonator (CSRR), first polyimide (PI) spacer, continuous VO 2 film, second PI spacer, and gold substrate. The converter possesses a polarization conversion ratio higher than 0.9 and a bandwidth ratio of 81% in a range from 0.912 THz to 2.146 THz. When the temperature is above the insulator-to-metal transition temperature (approximately 68 °C) and VO 2 becomes a metal, the metasurface transforms into a wideband linear-to-circular polarization converter composed of the gold CSRR, first PI layer, and continuous VO 2 film. The ellipticity is close to −1, while the axis ratio is lower than 3 dB in a range of 1.07 THz–1.67 THz. The metadevice also achieves a large angle tolerance and large manufacturing tolerance.