High-Efficiency All-Optical Modulator Based on Ultra-Thin Silicon/Graphene Hybrid Waveguides

All-optical modulation plays a key role in next-generation optical processing and has attracted enormous attention worldwide. With extraordinary optoelectronic characteristics and friendly integration compatibility with various nanostructures, graphene shows great potential for ultrafast and energy-efficient all-optical modulation. Here, high-efficiency on-chip all-optical modulation is experimentally demonstrated based on ultra-thin silicon/graphene hybrid waveguides, which are complementary-metal-oxide-semiconductor-compatible and easy to fabricate. Owing to the enhanced light-graphene interaction enabled by the ultra-thin silicon photonic platform, the optical nonlinear absorption in graphene is greatly enhanced and a modulation depth of >2 dB is achieved with a saturation threshold of 0.9 pJ per pulse for a 50-mu m-long modulator. The measured modulation efficiency is as high as 0.052 dB mu m(-1). Furthermore, the proposed all-optical modulator has the potential to operate at a bandwidth of hundreds of gigahertz. The present hybrid integration of graphene on ultra-thin silicon photonic waveguides paves the way toward the applications of on-chip ultrafast and energy-efficient all-optical information processing.