Slow-light-enhanced energy efficiency for the graphene microheater on silicon photonic crystal waveguides

Slow light has been widely utilized to obtain enhanced nonlinearities, enhanced spontaneous emissions, and increased phase shifts owing to its ability to promote light-matter interactions. By incorporating a graphene microheater on a slow-light silicon photonic crystal waveguide, we experimentally demonstrated an energy-efficient graphene microheater with a tuning efficiency of 1.07 nm/mW and power consumption per free spectral range of 3.99 mW. The rise and decay times (10% to 90%) were only 750 ns and 525 ns, which, to the best of our knowledge, are the fastest reported response times for microheaters in silicon photonics. The corresponding record-low figure of merit of the device was 2.543 nW.s, which is one order of magnitude lower than results reported in previous studies. The influences of the graphene-photonic crystal waveguide interaction length and the shape of the graphene heater were also investigated, providing valuable guidelines for enhancing the graphene microheater tuning efficiency.