Graphite/graphene disk stack-based metal-free wideband terahertz absorber

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 θ ≈ 70 ∘ in all the polarization planes. The utilization of the graphene disk allows the tuning of absorber response by varying its chemical potential ( μ c ) . For 0 &lt;<!-- μ c &lt;<!-- 0.2 e V , the absorber provides broadband response. The narrowband response is obtained for μ c &gt; 0.2 e V 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.

Graphene-based dual-functional chiral metamirror composed of complementary 90° rotated U-shaped resonator arrays and its equivalent circuit model

“…Metastructures, containing a resonator per unit cell with single-layered geometry, have a limited number of reflection bands and broadband reflection properties. Multi-band or broadband metamirrors are typically designed by combining multiple resonators with different sizes into a super unit cell 22 or stacking resonators as a multilayer structure with resonators with different geometrical parameters and separate with dielectric spacers 9 , 23 .…”

Bipolar charge trapping for absorption enhancement in a graphene-based ultrathin dual-band terahertz biosensor

“…Their extraordinary properties made the implementation of cloaks 2,3 , invisible carpet 4 and a perfect lens 5 possible. The current research trends are moving in the direction of implementing the terahertz (THZ) devices like antennas 6 , sensors [7][8][9] , filters 10 and absorbers 11 . The purpose of implementing the THz absorbers is enabling the technology in spectroscopy 12 , detection and sensing 13 and many more 14 .…”

“…The recent implementations discuss about the development of narrowband sensors with multi-layered media with complex structures having large thickness 17,20,21 . Another challenge in the implementation of sensors is making the response independent of incident angle and polarization of the incident electromagnetic wave 7,11 . This feature enables the sensor to be used in the dynamic sensing systems which can be utilized in the handheld devices 22 .…”

“…Moreover, the implemented absorbing unit behaves as a perfect wideband reflector in between the absorption peaks, thus can be utilized in the frequency selective THz sources. Generally, the multiple or dual-band resonances are obtained in the complex multilayered structures 11,[37][38][39][40] . In comparison, the proposed ultrathin dual-band absorber can offer a geometry with less complexities.…”

“…The current research trends are moving in the direction of implementing terahertz (THZ) devices like antennas, 6 sensors, 7–9 filters 10 and absorbers. 11 The purpose of implementing THz absorbers is enabling the technology in spectroscopy, 12 detection and sensing 13 and many more applications. 14 Recently, the implementation of ultrathin, 15 ultrasensitive 8,13,16,17 absorption based sensors/biosensors with a narrow 17,18 and ultra-narrowband 19,20 response is being investigated.…”