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 m²/(V⋅s). Additionally, the maximum group index (2079) of this device is achieved at the 1.0 eV Fermi level and the 4.5 m²/(V⋅s) 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.