Optimization of laser stabilization via self-injection locking to a whispering-gallery-mode microresonator: experimental study

TL;DR

This paper demonstrates how self-injection locking to a microresonator can significantly stabilize and narrow the linewidth of diode lasers, enabling precise frequency control and applications like long-range LIDAR.

Contribution

It provides an experimental and analytical study of laser stabilization via self-injection locking to whispering-gallery-mode microresonators, including control of frequency tuning and modulation capabilities.

Findings

Achieved laser linewidths of 1 Hz using microresonator locking.

Demonstrated fine frequency tuning through locking phase control.

Enabled sub-micrometer velocity measurements with stabilized lasers.

Abstract

Self-injection locking of a diode laser to a high-quality-factor microresonator is widely used for frequency stabilization and linewidth narrowing. We constructed several microresonator-based laser sources with measured instantaneous linewidths of 1 Hz and used them for investigation and implementation of the self-injection locking effect. We studied analytically and experimentally the dependence of the stabilization coefficient on tunable parameters such as locking phase and coupling rate. It was shown that precise control of the locking phase allows fine tuning of the generated frequency from the stabilized laser diode. We also showed that it is possible for such laser sources to realize fast continuous and linear frequency modulation by injection current tuning inside the self-injection locking regime. We conceptually demonstrate coherent frequency-modulated continuous wave LIDAR over a distance of 10 km using such a microresonator-stabilized laser diode in the frequency-chirping regime and measure velocities as low as sub-micrometer per second in the unmodulated case. These results could be of interest for cutting-edge technology applications such as space debris monitoring and long-range object classification, high resolution spectroscopy and others.