  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.
