BANDWIDTH LIMITATION AND DISTINCT OPERATING REGIMES OF PASSIVELY MODE-LOCKED DYE-LASERS USING STRONG PHASE SHAPING

The role of bandwidth limitation in passively mode-locked dye lasers is examined for the case in which strong phase shaping is combined with conventional amplitude shaping by saturable gain and saturable absorption. Numerical methods and recent experimental evidence for passively mode-locked dye lasers reveal three distinct operating regimes, which can be reached by varying the strength of the amplitude shaping and consequently the degree of bandwidth limitation. For weak amplitude shaping the pulse evolution can closely approximate that of higher-order solitons of the nonlinear Schrodinger equation. For strong amplitude shaping the laser produces stable trains of pulses with durations that are the shortest obtainable directly from a laser oscillator for a given bandwidth of the intracavity spectral filter and a given strength of amplitude shaping. For amplitude shaping of intermediate strength the laser exhibits complex pulse evolutions, which are not describable either by conventional mode-locking theory or by the nonlinear Schrodinger equation.