Polarization influence and its mitigation on laser frequency noise measurement by a short-delayed self-homodyne...

This paper investigated how a polarization state influences frequency noise measurement accuracy of the short-delayed self-homodyne interference method. An autopolarization control method was demonstrated to mitigate polarization-induced fading (PIF) in a 120-deg phase difference Mach-Zehnder Interferometer (MZI). This method used a feedback adjustment with simulated annealing algorithm, which had the advantages of a short control period, high accuracy, and easy implementation. Frequency fluctuations' power spectral density and linewidth results measured by the improved MZI were consistent with the results of the Michelson interferometer, which used the Faraday rotator mirrors (FRMs) to overcome PIF. The novel MZI structure is unrestricted to FRMs and can extend the capability of the short-delayed self-homodyne interference technique for many special bands' laser frequency noise measurements such as visible bands.