Laser diode self-injection locking to an integrated high-Q Fabry-Perot microresonator

TL;DR

This paper demonstrates the extension of self-injection locking to chip-integrated high-Q Fabry-Perot microresonators, achieving thermorefractive-noise-limited narrow-linewidth laser operation with a scalable fabrication process.

Contribution

It introduces a novel SIL approach using chip-integrated Fabry-Perot microresonators with a theoretical model and experimental validation, advancing chip-scale low-noise lasers.

Findings

Achieved thermorefractive-noise-limited laser linewidths

Demonstrated precise SIL tuning via evanescent coupling

Validated theoretical model with experimental results

Abstract

Self-injection locking (SIL) of laser diodes to microresonators is a powerful technique that enables compact narrow linewidth lasers. Here, we extend this technique to chip-integrated Fabry-Perot microresonators, which offer high-quality factors and large mode volumes in a compact footprint, reducing fundamental thermo-refractive noise. The resonators consist of a silicon nitride waveguide terminated by two photonic crystal reflectors fabricated via scalable ultraviolet lithography. Evanescent side-coupling allows precise tuning of the SIL feedback mechanism. We present a theoretical model and experimentally demonstrate SIL, resulting in a fundamental thermorefractive-noise-limited laser. We achieve excellent agreement between the experimental results and theoretical model. These results complement current SIL techniques and are relevant to chip-scale low-noise laser systems.