  Self-heterodyne beat note measurements are widely used for the experimental
characterization of the frequency noise power spectral density (FN-PSD) and the
spectral linewidth of lasers. The measured data, however, must be corrected for
the transfer function of the experimental setup in a post-processing routine.
The standard approach disregards the detector noise and thereby induces
reconstruction artifacts, i.e., spurious spikes, in the reconstructed FN-PSD.
We introduce an improved post-processing routine based on a parametric Wiener
filter that is free from reconstruction artifacts, provided a good estimate of
the signal-to-noise ratio is supplied. Building on this potentially exact
reconstruction, we develop a new method for intrinsic laser linewidth
estimation that is aimed at deliberate suppression of unphysical reconstruction
artifacts. Our method yields excellent results even in the presence of strong
detector noise, where the intrinsic linewidth plateau is not even visible using
the standard method. The approach is demonstrated for simulated time series
from a stochastic laser model including 1/f-type noise.
