High‐Performance All‐Optical Modulator Based on Graphene‐Loaded Ultrathin Silicon Slot Waveguides

All‐optical modulators can operate in an ultrafast way without limitation of the “electric bottleneck,” showing great potential applications in ultrabroadband communication and artificial intelligence. However, it remains as a persistent challenge for realizing ultrafast and energy‐efficient all‐optical modulation, especially on silicon photonic platform though CMOS‐compatible manner. Herein, a novel scheme composed of graphene‐loaded ultrathin silicon slot waveguide is demonstrated, realizing efficient and ultrafast all‐optical modulation on silicon photonic platform. Owing to the enhanced light–matter interaction and suppression of two‐photon absorption, the device shows a measured modulation depth over 3 dB with a potential maximum value of 6.9 dB, a modulation efficiency of 0.086 dB μm −1 , and a low saturation threshold energy of 0.88 pJ per pulse with a response time at picosecond scale or less. To the best of our knowledge, the device shows the best comprehensive performance with regard to the modulation efficiency and modulation depth among all silicon‐waveguide‐integrated all‐optical modulators operating at a speed in the picosecond scale or less. Besides, the structure deployed is fabrication friendly and CMOS compatible. The presented work provides a novel strategy for realizing energy‐efficient and ultrafast all‐optical modulators on silicon photonic platform, paving the way toward on‐chip ultrafast and energy‐efficient photonic processing.