Use of second-harmonic generation in mode locking of continuously operating solid-state lasers

An analysis is made of effective mode locking in continuously operating solid-state lasers by modulators based on second-harmonic generation. A new type of modulator is proposed in which a radiation field replica, attenuated as a result of harmonic generation, is subtracted interferometrically from the field. In principle, the proposed modulators can ensure more effective mode locking because of optimisation of the initial modulator transmission and because the intensity derivative of the transmission is used. Self-consistent solutions of a system describing continuous generation of ultrashort pulses are obtained and are shown to agree with the results of an analysis of the lasing dynamics based on the fluctuation model.