Theory of sub-10 fs Generation in Kerr-lens Mode-locked Solid-State Lasers with a Coherent Semiconductor Absorber

The results of the study of ultra-short pulse generation in continuous-wave Kerr-lens mode-locked (KLM) solid-state lasers with semiconductor saturable absorbers are presented. The issues of extremely short pulse generation are addressed in the frames of the theory that accounts for the coherent nature of the absorber-pulse interaction. We developed an analytical model that bases on the coupled generalized Landau-Ginzburg laser equation and Bloch equations for a coherent absorber. We showed, that in the absence of KLM semiconductor absorber produces 2pi - non-sech-pulses of self-induced transparency, while the KLM provides an extremely short sech-shaped pulse generation. 2pi- and pi-sech-shaped solutions and variable-area chirped pulses have been found. It was shown, that the presence of KLM removes the limitation on the minimal modulation depth in absorber. An automudulational stability and self-starting ability were analyzed, too.