Nonlinear total internal reflection and its utilization in ruby laser mode locking

Nonlinear total internal reflection was observed experimentally when a solution of phototropic dye was used as the optically rarer medium. This effect was used for Q switching and mode locking in solid-state lasers. A train of ultrashort pulses modulated to a depth close to 100% was obtained for a ruby laser in a plane-minor resonator pumped at a level 1–2% higher than the threshold.