Experimental and theoretical studies of complex pulse evolutions in a passively mode-locked ring dye laser

A detailed experimental and theoretical study has been made of the role of group velocity dispersion and self-phase modulation arising from time-dependent absorption saturation and the optical Kerr effect in a Rhodamine 110 CPM dye laser. Periodic pulse evolutions are observed, when both positive and negative frequency chirp are present, that are reminiscent of those governed by the nonlinear Schrodinger equation but that are, in fact, distinctly different. Similar results have been obtained with the standard Rhodamine 6G system, and it is believed that the theoretical model is generally applicable to any passively mode-locked femtosecond dye laser. An important consequence of these results is that they permit the absolute value of the group velocity dispersion in the laser cavity to be estimated