Multifunctional terahertz device based on a VO 2 -assisted metamaterial for broadband absorption, polarization conversion, and filtering

Abstract

This paper proposes a multifunctional terahertz device based on VO 2 with a simple structure that needs only one step lithography. The designed device can realize broadband absorption, reflective broadband cross-polarization conversion, reflective linear-to-circular polarization conversion, transmissive narrowband cross-polarization conversion, and filtering under different working conditions. When VO 2 is in a metallic state, the device can perform two different functions depending on the direction of the incident wave. When the electromagnetic wave is a forward incident, the device is a broadband absorber in the frequency range from 3.53 THz to 9.68 THz with a corresponding absorption efficiency above 90% and a relative bandwidth of 93%. When the electromagnetic wave is a backward incident, the device can work as a reflective broadband cross-polarization converter in the frequency range from 0.77 THz to 1.79 THz with a polarization conversion rate greater than 97% and a relative bandwidth of 80% and a reflective linear-to-circular polarization converter at 0.66 THz and 1.86 THz. While for VO 2 in the insulating state, the device exhibits the transmissive narrowband cross-polarization converter with polarization conversion rate greater than 90% at 1.32 THz and the function of the transmissive narrowband filter with transmittance more than 60% at 1.84 THz for both forward and backward incident waves. This multifunctional device may have great potential in miniaturized terahertz systems.