Phase effects in intracavity doubling of the frequency of ultrashort pulses

An investigation was made of intracavity generation of the second harmonic in a YAG:Nd³⁺ laser with active mode locking. Quasiperiodic dependences of the second harmonic energy on the phase mismatch in a nonlinear crystal and on the position of this crystal in the resonator were determined experimentally and theoretically. It was found that a laser with intracavity second harmonic generation was a self-consistent system and a suitable selection of its parameters could reduce considerably the duration of the harmonic pulses while retaining a fairly high conversion efficiency.