A comparison of Michelson and Mach-Zehnder interferometers for laser linewidth measurements

The performances of the Michelson (MI) and Mach-Zehnder interferometers (MZI) are compared for laser linewidth measurement with the delayed self-heterodyne technique. Voigt fitting is used to extract the Lorentzian and Gaussian components for the MZI and MI with faraday mirrors and also standard gold mirrors. The MI with Faraday mirrors provides a measurement with significantly lower error, owing to the elimination of noise associated with random polarisation drifts.