A bidirectional broadband multifunctional terahertz device based on vanadium dioxide

We propose a switchable and bidirectional metamaterial terahertz absorber/reflector based on vanadium dioxide. Simulation results show that the device can achieve broadband absorption and reflection by adjusting the phase state of vanadium dioxide. When the vanadium dioxide is in the insulating phase, the device can be a perfect bidirectional broadband absorber with more than 90% absorptivity under normal forward/backward TE/ TM-polarized incident wave in the frequency range from 1.9 THz to 10 THz. This excellent absorption characteristic is insensitive to the polarization angle of the incident wave. When the vanadium dioxide is in the metal phase, the device achieves more than 90% reflectivity in the low-frequency range under forward/backward TEpolarized incident wave. In the high-frequency range, the device has both reflection and absorption effects on the TE-polarized wave. When vanadium dioxide is in two different phase states, the performance of device is not sensitive to the electromagnetic wave incidence angle. The change in vanadium dioxide conductivity does not affect the stable performance of the device at high (low) frequencies when used as an absorber (reflector). The proposed device has potential applications in terahertz energy harvesting, detection, sensing, optical switching, and shielding.