Refined method to extract frequency-noise components of lasers by delayed self-heterodyne

TL;DR

This paper introduces a simple, cost-effective delayed self-heterodyne method for accurately extracting laser frequency noise components, providing a practical alternative to complex phase measurements for laser stability analysis.

Contribution

The work presents a novel application of the delayed self-heterodyne technique to measure laser frequency noise, demonstrating high accuracy with shorter delay lengths than the coherence length.

Findings

DSH trace correlates with FN PSD from commercial instruments

Method achieves discrepancies below 0.2% in dither tone frequencies

Applicable to multiple laser types for stability assessment

Abstract

An essential metric to quantify the stability of a laser is its frequency noise (FN). This metric yields information on the linewidth and on noise components which limit its usage for high precision purposes such as coherent communication. Its experimental determination relies on challenging optical phase measurements, for which dedicated commercial instruments have been developed. In contrast, this work presents a simple and cost-effective method for extracting FN features employing a delayed self-heterodyne (DSH) setup. Using delay lengths much shorter than the coherence length of the laser, the DSH trace reveals a correspondence with the FN power spectral density (PSD) measured with commercial instruments. Results are found for multiple lasers, with discrepancies in intense dither tone frequencies below 0.2 percent