Hybrid integrated modulation bandwidth enhanced laser based on self-injection locking to an external high-Q microring reflector

We demonstrate a hybrid integrated laser with nearly two folds of direct modulation bandwidth enhancement and 150 folds of linewidth reduction, by introducing the photon-photon resonance effect and self-injection locking effect to a commercial DFB laser simultaneously through an external high-Q silicon nitride microring reflector (MRR). Different from the widely studied passive feedback lasers, the proposed high-Q MRR keeps the DFB laser in the strong self-injection locking state, which can achieve stable narrow linewidth single-mode output with high Side-Mode Suppression Ratio. After packaging the proposed hybrid laser, we measure its direct modulation bandwidth and linewidth, which are increased from 7.70GHz to 15.28GHz, and reduced from 600kHz to 4kHz, respectively. This work explores a compact footprint and low-cost modulation bandwidth enhancement and linewidth reduction scheme for many applications such as high-speed coherent optical communication and microwave photonics.