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.
CW passive mode-locking evolved from Q-switched mode-locking in erbium doped fiber lasers
Summary form only given. We report a new mode-locking mechanism, where the use of a two-photon absorber in addition to a saturable absorber allows for CW mode-locking to reliably evolve from Q-switched mode locking. An optimal design of the two-photon absorber limits the peak power of the Q-switched pulses via optical limiting and thus aids in preventing damage to the saturable absorber. Moreover, the threshold for optical limiting is chosen to set an optimum stability point for CW mode-locked operation.
Degenerate four-wave interaction in a resonant medium allowing for variation of the pump waves
A theoretical analysis is made of the efficiency of wavefront reversal under conditions of a degenerate form of the four-wave interaction in a resonantly absorbing (amplifying) medium allowing for changes in the pump waves as a result of their natural resonant absorption (amplification). The coefficient of reflection into a reversed wave is obtained as a function of the optical thickness of a layer of the medium, the boundary values of the pump wave intensity, and the shift of the field frequency from the line center. The optimal values of these parameters and the corresponding maximum reflection coefficient are determined.