The research paper entitled "Reliable intracavity reflection for self-injection locking lasers and microcomb generation" was recently published in the journal Photonics Research, reporting the latest results on hybrid integrated narrow linewidth lasers.

Narrow linewidth lasers have important applications in coherent communications, microwave photonics, optical clocks, precision measurements and other fields. Among them, narrow linewidth lasers based on self-injection locking are expected to realize fully on-chip integrated highly coherent light sources, which have attracted much attention in recent years. In the self-injection-locked laser scheme, the laser cavity is made to be directly connected to the high-quality-factor resonant cavity, and when the high-quality-factor cavity can provide reflection peaks with narrow linewidths, the reflection from the high-quality-factor resonant cavity will pull the output laser from the laser cavity. Under suitable operating conditions, the laser output laser frequency will be locked to the resonant frequency of the high quality factor cavity, thus realizing the suppression of laser phase noise.

In conventional schemes, reflection from a high-quality factor cavity can be introduced by relying on Rayleigh scattering from the cavity, but this backscattering mechanism is stochastic in nature. In this work, a reliable reflection mechanism introducing a self-reflecting structure within an on-chip micro-ring resonant cavity is proposed, which can realize reliable reflection within a wide spectrum and thus support self-injection-locked lasers at different wavelengths. Further combined with intracavity optical nonlinear effects, self-injection-locked microcavity optical comb excitation can be realized. This work paves the way for wafer-scale preparation of high-coherence light sources based on self-injection locking.

Link to the original paper:

https://doi.org/10.1364/PRJ.511627