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

Abstract 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‐µm‐long modulator. The measured modulation efficiency is as high as 0.052 dB µm⁻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.