Linewidth narrowing and frequency stabilization of a coin-sized laser module

We demonstrate linewidth narrowing and frequency stabilization of a coin-sized laser module using both a short imbalance path length Michelson fiber interferometer and Doppler-free spectroscopy of molecular iodine. The linewidth of the coin-sized laser is reduced from 2 MHz to 6 kHz, which is now narrower than the Doppler-free spectral linewidth (670 kHz) of molecular iodine. Laser frequency stabilization based on the Doppler-free iodine signal is carried out by directly controlling the imbalance path length of the fiber interferometer. The frequency stability of the hybrid-locked coin-sized laser is 9.8 x 10(-13) at 1-s averaging time and reaches 6.8 x 10(-14) at 400 s. The hybrid-locked coin-sized laser with linewidth narrowing and frequency stabilization has a long coherence time and known absolute frequency and can be used for precision measurements in either fundamental science or industrial applications. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement