Polarisation-independent switchable absorber/reflector

A polarisation-independent switchable absorber/reflector based on active frequency selective surface (AFSS) has been reported. The FSS design consists of diagonally connected circular loops on which semiconductor switches (PIN diodes) have been mounted. By controlling the bias voltage of the PIN diodes, the structure shows perfect reflection in ON state while exhibits single band absorption during OFF state. The proposed design is four-fold symmetric, thereby realising polarisation-insensitive behaviour, unlike the earlier reported AFSS designs. Furthermore, a prototype of the proposed structure has been fabricated where the PIN diodes have been biased through a novel biasing technique. The measured result also shows good agreement with simulated response under normal incidence.