Polarization-sensitive asynchronous switch and notable slow-light based on tunable triple plasmon-induced transparency effect

Abstract

We have achieved a tunable triple plasmon-induced transparency (PIT) effect on a metasurface aligned with continuous graphene strips. We also introduce coupled mode theory (CMT) as an explanation of the triple-PIT, obtaining theoretical calculation data consistent with time-domain finite-difference method (FDTD) simulations. A five-frequency asynchronous switch is developed by exploiting the sensitivity of the PIT to polarized light, and the modulation depths at the five resonance frequencies can reach 85.5 %, 83.03 %, 84.7 %, 87.5 %, and 79.8 %, respectively. Notably, altering the length of certain bright modes within the structure, either increasing or decreasing the length, will lead to the degradation of the triple-PIT to a double-PIT. Furthermore, it is demonstrated that the structure exhibits outstanding slow-light performance, possessing a group refractive index above 1000. Our findings thus offer a theoretical foundation for further investigation into high-performance slow light devices as well as multi-frequency modulators operating at terahertz frequencies.