Graphene-based active tunable mode splitting in an indirectly coupled photonic crystal nanobeam cavity–waveguide system

Abstract

We propose an indirectly coupled photonic crystal nanobeam (PCN) cavity–waveguide system that consists of two PCN cavities indirectly coupled to each other through a bus waveguide and numerically investigate the mode splitting phenomenon by varying the coupling strength between two cavities. By placing graphene sheets on top of one of the cavities and tuning the Fermi level of graphene, the active control of the mode splitting is achieved without reoptimizing or readjusting the structures. A theoretical model based on the coupled mode theory is further exploited to unveil the physical mechanism behind such a graphene-based active tunable mode splitting phenomenon. Furthermore, active modulation of the group delay is also demonstrated by changing the Fermi level of graphene, achieving a well-controlled slow light effect. Our proposed system is expected to provide a broad range of photonics applications in slow light devices, optical switching, monitoring, and optical sensing.