Robust Laser Phase Noise Reduction by Tracking Frequency Discrimination Change of Interferometer

We present a robust interferometer-based laser phase noise reduction technique that can easily be tuned to apply phase corrections at frequencies at which the interferometer is less affected by environmental disturbances. The technique operates by measuring the in-phase and quadrature components of the interference pattern along the circular Lissajous figure to compute the short-term phase error and reject long-term interferometer drift, and then uses that phase error to correct the laser phase noise. We successfully demonstrate phase noise reduction for an external cavity semiconductor laser without the need for an interferometer stabilization technique. The proposed technique realizes a frequency noise reduction about 20 dB between 100 Hz and 3 MHz. We also investigate the imbalance of the circular Lissajous figure and show that the performance degradation caused by an amplitude imbalance and a phase deviation from 90° can be compensated for by amplifying the extracted phase noise fluctuation.