Stabilization of narrow-band operation of semiconductor DFB laser self-injection locked to a PM fiber ring cavity

This work presents a scheme for narrowing and stabilizing the narrow-band emission of a distributed feedback semiconductor laser diode achieved through its self-injection locking to an external fiber ring cavity. A distinctive feature of this laser configuration is its implementation using polarization-maintaining fibers (PM fibers) and an additional optoelectronic feedback system based on a low-cost USB-DAQ controller. These novel technical solutions have enabled a narrowing of the laser Lorentzian linewidth to ∼75 Hz while reducing the phase noise by ∼30 dB. Owing to a design composed of standard PM fiber components and the absense of polarization controllers, the new laser configuration does not need tuning and offers enhanced resistance to environmental noise. The proposed laser design is promising for many applications that demand a combination of a narrow (below 1 kHz) lasing linewidth, structural simplicity, and cost-effectiveness.