Generation of a train of ultrashort pulses with controlled parameters

An analysis is made of the mode self-locking process in solid-state lasers and the emission noise pattern at the end of the linear stage is shown to be a superposition of the noise patterns emitted during a large number of passes of the field along the resonator, after the threshold condition has been satisfied. To improve the reproducibility of parameters of the ultrashort pulses, a proposal is made to reduce the number of lasing modes by thinning out the lasing spectrum without increasing its width. This method can be used to provide reproducible pulse parameters and to control the pulse characteristics, including the pulse-train envelope. A neodymium glass laser was investigated experimentally which produced ultrashort pulses having a repetition period controllable over the range 20 psec to 25 nsec.