Passive negative feedback in mode-locked solid-state lasers

Passive negative feedback by an intracavity GaAs platelet in actively/passively mode-locked solid-state lasers is reexamined, and the role of both single- and two-photon absorption in determining the features of the pulses and the pulse train is explored and compared with the experimental results. The time-bandwidth product is shown to acquire in the steady-state part of the train a value close to the minimum allowed by the uncertainty relation.