Tunable terahertz slow-light device based on triple plasmon-induced transparency on a patterned graphene metasurface

The present study proposes a reconfigurable metasurface comprising four graphene rectangles together with five graphene strips, designed to achieve triple plasmon-induced transparency (PIT). The coupled mode theory-based theoretical analysis demonstrates a high level of agreement with finite-difference time-domain simulation results. This graphene-based triple-PIT device enables dynamic tuning of its Fermi level and carrier mobility. For the prepared triple-PIT system, the group index varies from 1134 to 2020 with increasing graphene Fermi level in the range of 0.8-1.2 eV. Conversely, the group index ranges from 1123 to 2079 with increasing graphene carrier mobility in the range of 2.5-4.5 m^2/(V\cdots). Additionally, the maximum group index (2079) of this device is achieved at the 1.0 eV Fermi level and the 4.5 m^2/(V\cdots) carrier mobility, which markedly exceeds that of conventional terahertz slow-light structures. Furthermore, the device exhibits good tolerance to design and fabrication deviations. It thus provides useful design guidance for high-performance terahertz slow-light devices.