Improved laser linewidth estimation from self-heterodyne beat note measurements using parametric Wiener filters

Abstract

Self-heterodyne beat note measurement techniques are widely used for the experimental char- acterization of the phase noise power spectral density (PSD) and the spectral linewidth of lasers. The measured data, however, must be corrected for the transfer function of the interferometer in a post-processing routine. The standard approach disregards the measurement noise and thereby induces uncontrolled artifacts in the reconstructed noise PSDs. We introduce an improved data post-processing routine based on a parametric Wiener filter (power spectrum equalization, PSE), that is potentially free of reconstruction artifacts provided a good estimate for the signal-to-noise ratio (SNR) is supplied. Based on the PSE filter, we describe a new method for the estimation of the intrinsic laser linewidth. Our method yields accurate estimates even in the case of strong measurement noise, where the intrinsic linewidth plateau is not visible using the standard method. We demonstrate the method using simulated data from a stochastic laser rate equation model.