An agile laser with ultra-low frequency noise and high sweep linearity

TL;DR

This paper presents a fiber-stabilized agile laser with ultra-low frequency noise and high linearity in frequency sweep, achieved through analysis and mitigation of Rayleigh backscattering effects.

Contribution

The work introduces a novel fiber-stabilized laser with ultra-low frequency noise and high linearity, including techniques to reduce Rayleigh backscattering noise.

Findings

Frequency noise comparable to ultra-stable cavity lasers at >30 Hz

Achieved 50 Hz peak-to-peak non-linearity over 600 MHz range

Identified and mitigated Rayleigh backscattering as a noise source

Abstract

We report on a fiber-stabilized agile laser with ultra-low frequency noise. The frequency noise power spectral density is comparable to that of an ultra-stable cavity stabilized laser at Fourier frequencies higher than 30 Hz. When it is chirped at a constant rate of ~ 40 MHz/s, the max non-linearity frequency error is about 50 Hz peak-to-peak over more than 600 MHz tuning range. The Rayleigh backscattering is found to be a significant frequency noise source dependent on fiber length, chirping rate and the power imbalance of the interferometer arms. We analyze this effect both theoretically and experimentally and put forward techniques to reduce this noise contribution.