Photo-Induced Thermo-Optical Refraction Switching by a Graphene-Assisted Silicon Microring Resonator

We demonstrate the in-plane photo-induced thermo-optical refraction switching using a silicon all-pass microring resonator (APMRR) assisted by graphene. The optimized design of low-doped graphene on an overcoupled APMRR realizes nearly critical coupling with an extinction ratio of 21 dB. For an input power of 250 
$\mu W$
, a high modulation of resonance with a tuning efficiency of 216 pm/mW and an extinction ratio contrast of 10 dB is realized relying on nearly critical coupling of APMRR and large electrical conductivity of graphene. Furthermore, the typical switching performance with a 0.2-
$\mu s$
rise time and a 1.5-
$\mu s$
fall time following the 10%–90% rule is obtained by direct pumping of light and large thermal conductivity of graphene. This proposed device with ease of fabrication and integration, low power consumption, and short response time shows great potential for totally planar photonic integrated circuits.