  A broadband chaotic laser with a flat power spectrum extending up to 8.5GHz
is achieved by injecting continuous wave laser light into a chaotic diode laser
perturbed by fiber random grating induced distributed feedback, which forms a
gain-coupled chaotic laser system. More than triple bandwidth enhancement is
realized with appropriate frequency detuning between the master and slave
lasers. Unlike normal chaotic lasers, the output from such a broadband chaotic
laser is free from time-delay signature, which can be applied for practical
real-time random number generations and will find useful applications in the
fields of information security and computation systems.
