Ultra Low Frequency Noise Laser Stabilized On Optical Fiber Spool

In this paper, the development of an ultra low frequency noise laser has been presented. This laser is obtained by frequency stabilizing a fiber laser to a 1-km fiber length-unbalanced Michelson interferometer with heterodyne detection configuration. The laser frequency noise power spectral density is reduced by more than 40 dB for Fourier frequencies ranging from 1 Hz to 10 kHz, corresponding to a level well below 1 Hz²/Hz over the whole range. Between 30 Hz and 10 kHz, the frequency noise of the laser is shown to be comparable to that obtained by Pound-Drever-Hall locking of the laser to an ultra-stable cavity. Moreover this laser has the great advantage of no optical alignment and no polarization adjustment due to the utilization of an all-fiber system. It is therefore intrinsically more compact, light, robust and flexible than cavity-based systems. This stabilization technique allows the frequency tunability of the low noise laser.