Threshold self-start of laser passive mode-locking under conditions of high-order frequency dispersion of the refractive index

The dependence of the self-start of laser passive mode-locking on the peak intensity of initial pulses under conditions of high-order frequency dispersion of the refractive index is analyzed using numerical simulation and analytical calculations. It is found that frequency dispersion of this type can lead to generation bistability. Specifically, laser passive mode-locking requires the generation of a sufficiently intense seed pulse in the initial noise distribution of the field in the laser cavity; otherwise, no laser passive mode-locking occurs and a steady-state lasing mode with the entire laser cavity filled with radiation is established in the system after the transient process is completed. The revealed threshold dependence of the self-start of laser passive mode-locking on the intensity of the initial seed pulse is one of the possible factors preventing the generation of ultrashort pulses in Kerr-lens lasers.