Sub-kilohertz hybrid integrated InP-Si 3 N 4 laser with a single microring resonator

Abstract Output optical characteristics of miniature highly stable hybrid integrated lasers were experimentally investigated. The devices are assembled in an industrial form factor using a multi-frequency semiconductor laser coupled with an external microring resonator (MRR). An expression for the coupling coefficient between the laser diode and the ring resonator is derived, taking into account the butt coupling efficiencies and reflection from the MRR. For two lasers with different MRRs the level of low-frequency thermorefractive noise is estimated and the instantaneous linewidth values are calculated and experimentally measured, yielding 200 Hz and 900 Hz, which are comparable to those of best commercially available analogues. The good agreement between theoretical and experimental data confirms the validity of the model used.