Efficiency of Self-Injection Locked Lasers

The integrated III-V self-injection locked (SIL) laser exhibits excellent linewidth compression, noise reduction, and frequency stability. However, the laser’s low efficiency and fluctuating output power severely limit its applications in optical coherent transmission, light detection and ranging (LiDAR), spectroscopy, and so on. Based on the rate equations for a semiconductor laser coupled to counter-propagating fields in a micro-ring resonator (MRR), we systematically investigate the laser power and linewidth compression under self-locking conditions. We improve the slope efficiency by adjusting the injection phase, diode–MRR coupling efficiency, the normalized mode-coupling rate between clockwise (CW) and counter-clockwise (CCW) modes, and the MRR Q-factor. The results show that the enhanced diode–MRR coupling efficiency effectively increases the laser slope efficiency and improves the stability of the injection phase and feedback intensity. The injection phase significantly influences the range of the self-injection locked state. The normalized mode-coupling rate effectively affects the locking bandwidth and maintains stable power transfer. The MRR intrinsic Q-factor has a positive correlation with improving the laser slope efficiency and compressing the linewidth.