Recent advances in stabilization of mode-locked quantum dash lasers at 1.55 µm by dual-loop optical feedback

Abstract This paper reports the effectiveness of a variety of single- and dual-loop optical feedback arrangements on stability of self-mode-locked two-section quantum dash lasers emitting at ≈1.55 µm and operating at 21 GHz repetition rate. We describe reduction of RF linewidth and timing jitter using five distinct schemes, including single and dual loops with symmetric and asymmetric lengths, and with balanced and unbalanced feedback ratios. All feedback schemes described are effective in stabilizing the pulse trains from SML QDash lasers, but some require precisely tuned resonance between loop delay and laser cavity. We show balanced asymmetric dual-loop optical feedback is the most robust, cost-effective and low-noise method to stabilize and control pulses from mode-locked lasers and optoelectronic oscillators.