All-Optical Modulation of a Graphene-Cladded Silicon Photonic Crystal Cavity

The combination of graphene and a silicon photonic crystal cavity provides an ideal structure for realizing sensitive all-optical modulation. In this paper, an all-optical tuning of a graphene-cladded photonic crystal cavity is demonstrated. A 3.5 nm resonance wavelength shift and a 20% quality factor change are observed as a 1064 nm continuous-wave control laser is focused on the cavity. The resonance wavelength shift is nearly 2 times that realized with electrical modulation and can be further improved with increasing laser power. Meanwhile, it is found that the laser power to reach the saturation absorption state of graphene is nearly 2 orders of magnitude lower than that for monolayer graphene on silica. The experimental results are attributed to optically induced transparency and hot carrier effects. This study opens up a promising way to construct a sensitive all-optical modulator, which is a necessary device in an all-optical integrated circuit, by using a graphene-cladded photonic crystal cavity.