Abstract

A wideband terahertz metal-free absorber is designed and numerically analyzed. The graphite/graphene disks supported by low permittivity dielectric disks are stacked. The stacked graphite disks are placed above a dielectric substrate acting as resonant cavity. The resonance of dielectric cavity is merged with the resonance of a graphite and graphene disk for obtaining the wide absorption band. The obtained response from numerical simulation is verified with the response obtained by an equivalent circuit model based on the transmission line method. The proposed absorber provides a simple and compact geometry with polarization insensitivity. The proposed absorber maintains high absorption over a wide range of variation in the incident angle $\theta \approx 70^\circ $ in all the polarization planes. The utilization of the graphene disk allows the tuning of absorber response by varying its chemical potential $( {{\mu _c}})$. For $0 \lt {\mu _c} \lt 0.2\;{\rm eV}$, the absorber provides broadband response. The narrowband response is obtained for $\;{\mu _c} \gt 0.2\;{\rm eV}$ by suppressing the lower-order modes generated by the stack of graphite disk resonators. Moreover, the proposed technique enables implementation of metal-free wideband absorbers.

© 2021 Optical Society of America

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