Chaos spectrum -- semiconductor laser with delayed optical feedback

Maximizing the rf bandwidth associated with the chaotic output from tailored operation of nonlinear semiconductor laser systems is an ongoing research effort. The early pioneering research was done in semiconductor laser with delayed optical feedback systems, which continue to be researched. We report numerical simulations of this system, using a travelling wave model. The results provide new insights into the impact of key device parameters affecting the chaos bandwidth and spectrum. Linewidth enhancement factor and the nonlinear gain saturation parameter are found to be the most important parameters when seeking to optimize the chaotic output. We reassess a standard definition being used to report chaos bandwidth. We propose that more spectral information should be reported if numerical and experimental research results are to be of most value into the future. A database from previous experimental study is also analyzed to connect with the predictions of the numerical simulations. This elucidates the links between the chaos bandwidth achieved in real systems and the semiconductor laser parameters. The results inform recommendations for semiconductor laser parameters that will better support broadband chaos generation in whatever semiconductor-gain-medium-based nonlinear system approach is being used. They elucidate the physics of both the envelope and the fine structure of the rf spectrum of coherence collapse.