Power-area method to precisely estimate laser linewidth from its frequency-noise spectrum

We proposed a precise and simple method to estimate the laser linewidth from its frequency power spectral density, which is termed as power-area method (PAM). We applied this method to determine the full width at half-maximum (FWHM) of white-frequency noise and flicker-frequency noise, and the error was less than 7%. Then we successfully estimated the FWHM of the beat note of delayed self-homodyne/heterodyne interferometry with this method. Lastly we investigated the selection of loop gain and loop bandwidth using PAM to achieve a better result in linewidth compression with servo-loop control.