A Simple Ultrathin Quad Band Polarization Insensitive Metamaterial Absorber for Infrared Applications

A simple ultrathin quad band polarization insensitive metamaterial absorber has been reported in this paper. The unit cell of the proposed structure consists of dipoles of unequal lengths. The structure exhibits absorptions at 18.4 THz, 33.4 THz, 51.4 THz and 75.2 THz with respective absorptivity of 99.2%, 99.4%, 92.2% and 98.2%. Under oblique incidence the structure behaves as an absorber for both TE and TM polarizations so long as the angle of incidence is within 60°. The structure is ultrathin ~ λ/33 as well as compact in dimension ~λ/8 periodicity (corresponding to lowest frequency). The proposed quad band metamaterial absorber structure is expected to find potential application in THz spectroscopy, imaging techniques and sensing.