PULSE COLLIDING IN A SELF-MODE-LOCKED RING-CAVITY TI-SAPPHIRE LASER

A new self-mode-locked ring-cavity Ti:sapphire laser is described that is self-mode locked in both unidirectional and bidirectional operatio ns. We found that clockwise and counterclockwise pulses collide with e ach other at the Ti:sapphire rod when the laser is mode locked in a bi directional operation. Spectrum narrowing and pulse broadening were fo und in bidirectional rather than unidirectional mode-locked operation. This is explained by the performance of a transient grating in the ga in medium that restricts oscillation to a narrow spectral range. (C) 1 998 Optical Society of America.