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

TL;DR

This paper presents an asymmetric dual-loop feedback scheme for quantum dash lasers that effectively suppresses spurious tones and reduces timing jitter, leading to more stable and cleaner laser operation.

Contribution

The study introduces an optimized asymmetric dual-loop feedback method with large disparity in cavity lengths to eliminate side-modes and improve laser stability, validated by experimental results.

Findings

Complete suppression of external-cavity side-modes.

Significant reduction in RF linewidth and timing jitter.

Validation of numerical simulations with experimental data.

Abstract

We demonstrate an asymmetric dual-loop feedback scheme to suppress external cavity side-modes induced in self-mode-locked quantum-dash lasers with conventional single and dual-loop feedback. In this letter, we achieved optimal suppression of spurious tones by optimizing the length of second delay time. We observed that asymmetric dual-loop feedback, with large (~8x) disparity in cavity lengths, eliminates all external-cavity side-modes and produces flat RF spectra close to the main peak with low timing jitter compared to single-loop feedback. Significant reduction in RF linewidth and reduced timing jitter was also observed as a function of increased second feedback delay time. The experimental results based on this feedback configuration validate predictions of recently published numerical simulations. This interesting asymmetric dual-loop feedback scheme provides simplest, efficient and cost effective stabilization of side-band free optoelectronic oscillators based on mode-locked lasers.