Pulse shortening in a mode-locked YAG:Nd laser using the colliding pulse method

Mode locking in a pulsed YAG:Nd laser was studied using the colliding pulse method in a passive antiresonant ring interferometer. The results were compared with those obtained when a cell filled with a dye located next to a nontransmitting resonator mirror was used for mode locking. It was found that the colliding pulse method nearly halved the pulses, was characterized by good amplitude stability and short-term reliability, but suffered from poor long-term stability. Possible causes of the instability and also the mechanism of this pulse shortening are discussed.