Dynamic detuning in actively mode-locked semiconductor lasers

The authors describe a new limit on the achievable pulsewidth from actively mode-locked semiconductor lasers which is due to dynamic detuning. Dynamic detuning sets a higher limit on pulsewidth than the effects of finite gain bandwidth and dispersion, agreeing with experimental results which show pulsewidths much longer than expected if dynamic detuning is neglected. The dynamic detuning mechanism gives rise to the multiple-pulse output seen for all measurements of subpicosecond pulses and can lead to an unstable output waveform if a perfect antireflection coating is used. The analysis uses the traveling-wave rate equations to include a spatial variation in carrier and photon densities along the laser cavity and also includes the nonzero reflectivity on the antireflection-coated facet. The effects of phase at the antireflection-coated facet and dynamic carrier heating are included in the model