Measuring the linewidth of a stabilized diode laser

TL;DR

This paper presents a simple method to measure the linewidth of a stabilized diode laser by beating two lasers in an interferometer and analyzing the signal, demonstrating a linewidth of about 0.3 MHz.

Contribution

It introduces a straightforward technique for linewidth measurement of external cavity diode lasers using beat signals and Fourier analysis.

Findings

Linewidth of each ECDL is approximately 0.3 MHz over 2 μs.

The method effectively characterizes laser stability for high-resolution applications.

Demonstrates suitability of ECDLs for atomic physics experiments.

Abstract

We demonstrate a straight-forward technique to measure the linewidth of a grating-stabilized diode laser system---known as an external cavity diode laser (ECDL)---by beating the output of two independent ECDLs in a Michelson interferometer, and then taking the Fourier transform of the beat signal. The measured linewidth is the sum of the linewidths of the two laser systems. Assuming that the two are equal, we find that the linewidth of each ECDL measured over a time period of 2 \textmu s is about 0.3 MHz. This narrow linewidth shows the advantage of using such systems for high-resolution spectroscopy and other experiments in atomic physics.