Polarization and Wide Incident Angle Insensitive Metal Free Superwideband Absorber For Terahertz and Infrared Spectrum

Abstract A circular slot loaded octagonal metal free graphite based absorber for superwideband applications at terahertz and infrared spectrum is proposed. The absorber comprises a circular slot loaded octagonal graphite slab at the top layer, silicon dioxide as substrate and square graphite slab as the bottom layer. This absorber is operating over a frequency spectrum of 6 THz to more than 80 THz (ratio bandwidth of > 12:1 and fractional bandwidth of > 172.093%) for absorption more than 90% with unity peak absorption. The absorber dimensions are 5 µm × 5 µm × 7.04 µm. The thickness of the substrate is only ∼ λo/26 and the periodicity of absorber is ∼ λo/10 at 6 THz. The performance of the absorber is found to be insensitive to changes in polarization angle (Φ). Furthermore, the performance of the absorber is observed to be unaffected by incident angle (θ) variations from 0o to 60o. The metal-free geometry along with insensitiveness to Φ and 0o ≤ θ ≤ 60o makes the proposed absorber suitable for compact terahertz/infrared micro/nanoscale systems.