An asymmetric dual-loop feedback scheme with optimized second delay time to suppress spurious tones and timing jitter of self-mode-locked quantum dash lasers

摘要

We demonstrate an asymmetric dual-loop feedback scheme to suppress externalcavity side-modes induced in self-mode-locked quantum-dash lasers withconventional single and dual-loop feedback. In this letter, we achieved optimalsuppression of spurious tones by optimizing the length of second delay time. Weobserved that asymmetric dual-loop feedback, with large (~8x) disparity incavity lengths, eliminates all external-cavity side-modes and produces flat RFspectra close to the main peak with low timing jitter compared to single-loopfeedback. Significant reduction in RF linewidth and reduced timing jitter wasalso observed as a function of increased second feedback delay time. Theexperimental results based on this feedback configuration validate predictionsof recently published numerical simulations. This interesting asymmetricdual-loop feedback scheme provides simplest, efficient and cost effectivestabilization of side-band free optoelectronic oscillators based on mode-lockedlasers.