A pulse laser apparatus (100) for creating laser pulses (1), in particular soliton laser pulses (1), based on Kerr lens mode locking of a circulating light field in an oscillator cavity (10), comprises at least two resonator mirrors (11, 12, . . . ) spanning a resonator beam path (2) of the oscillator cavity (10), at least one Kerr-medium (21, 22, 23) for introducing self-phase modulation and self-focusing to the circulating light field in the oscillator cavity (10), at least one gain-medium (31) for amplifying the circulating light field in the oscillator cavity (10), and a tuning device (40) for setting a first mode-locking condition and a second mode-locking condition of the oscillator cavity (10) such that an intra-cavity threshold-power for mode-locking at the first mode-locking condition is lower than that at the second mode-locking condition, wherein the first mode-locking condition is adapted for starting or shutting-down of the Kerr lens mode locking and the second mode-locking condition is adapted for continuous Kerr lens mode locking and a resonator-internal peak-power of the circulating light field is higher at the second mode-locking condition than at the first mode-locking condition. Furthermore, a method of operating a pulse laser apparatus is described.