Featureless Broadband Chaos Through Cascaded Optically Injected Semiconductor Lasers

Optical chaos generated by a semiconductor laser under cascaded optical injection is experimentally and numerically investigated. A semiconductor slave laser under continuous-wave optical injection from a master laser is employed as the chaotic laser. The chaotic output optically injects a third laser to enhance the chaotic properties. Using three semiconductor lasers coupled in a master-slave configuration without any delay-based components, optical chaos is generated without any time-delay signatures present. Flat broadband chaos is observed with standard and effective bandwidths reaching six and three times the relaxation resonance frequency of the semiconductor laser, respectively. For simultaneous flat and broadband chaos, the chaotic optical injection of the second stage is adjusted for weak injection strength and a high positively detuned frequency.