Graphene-VO2-based-defect-induced tunable multiple narrowband unidirectional photonic terahertz absorber

Abstract

This work demonstrates a one-dimensional unidirectional terahertz (THz) absorber with thermal switching from broadband to narrowband and tunable multiple narrowband absorption with vanadium dioxide (VO2)-graphene-based defective photonic crystal. The thermal tuning of defect layer switches the phase of VO2 and obtain multiple narrowband optical absorptance with 70-90% peak at 4.12, 4.86 and 5.23THz respectively with a Q factor around 291 for 4.86 THz peak. The thermal dependent Q factor of the stack varies from 19 to 291 with phase transition from metal to the insulating state of the defect. The optical non-magnetic THz unidirectional absorber has switchable propagation functions within the metallic phase from non-absorption to higher peak absorption with forward and backward propagated wave. The asymmetrical dual defect layer with dual absorption peaks can be switched and the wavelength can be changed by changing the distance between the two peaks. Multiple graphene-based VO2 defects have increased peaks of narrowband absorption. This novel phase changing material (PCM) based asymmetric defective photonic layer can tune the defect layer for optimum and adjustable absorption at THz range and non-magnetic reciprocal and unidirectional structure with temperature dependent dual band switchable, which leads to this structure for terahertz wireless communication systems as well as other THz sensing devices.