Graphene layers for ultra-broadband and reconfigurable THz absorption: an analytical model and design procedure

An ultra-broadband dual-layer graphene absorber is analyzed and designed using a proposed rigorous analytical model in conjunction with an equivalent circuit model. Based on these models, a systematic design methodology has been developed and validated through the proposed analytical formulation, the equivalent circuit model, and two independent numerical simulation methods, all of which demonstrate excellent agreement. In addition to providing accurate analysis, the proposed analytical model offers deep physical insight into the influence of various design parameters on the performance of graphene-based THz absorbers. The designed absorber achieves greater than 95% uniform absorption over the frequency range of 0.5–2.55 THz, while maintaining absorption above 90% across an overall bandwidth extending from 0.44 to 2.6 THz, corresponding to a normalized bandwidth of 142%. Furthermore, the absorber exhibits exceptional reconfigurability. By tuning the Fermi levels of the graphene layers, the device can be configured to operate over the entire ultra-broadband frequency range, selectively target either the high-frequency or low-frequency region, or function as a broadband reflector. Owing to its moderate fabrication process, tunable response, and versatile operational characteristics, the proposed absorber is highly promising for emerging THz communication and sensing applications.