Dynamics of a semiconductor laser with frequency shifted feedback

Dynamics of the output of a semiconductor laser with frequency-shifted optical feedback system is systematically analyzed. Results from experimental studies using an 830 nm, QW, Fabry-Perot cavity, semiconductor laser are reported. The dynamics are mapped as a function of the level of frequency shifted feedback (FSF) and the injection current. The frequency shift of the optical feedback is the fundamental or a sub-harmonic of the external cavity frequency in the experiments. Multi-GHz-bandwidth real time data collection and analysis is used to investigate the temporal and spectral behaviour of the output power of the nonlinear system. The results are contrasted with those from conventional semiconductor laser with optical feedback systems. Three fundamentally different regimes of operation are identified for the FSF system corresponding to low, medium and high levels of FSF. The low and medium level FSF regimes are consistent with those found in the semiconductor with conventional optical feedback system. It is only when high levels of FSF are used that the output gives a noisy, near periodic output which is similar to the pulsed comb of mode output observed in analogous FSF laser systems using solid state gain media when the FSF is resonant.