Use of neodymium-activated niobium phosphate glasses in lasers with passive mode locking

Neodymium-activated niobium phosphate glasses, characterized by a narrow (4–6 cm^–1) stimulated emission band under free-oscillation conditions at room temperature, were used in a laser with passive self-locking of the modes. In this case the total width of the stimulated emission spectrum did not exceed 1.2–1.5 cm^–1. This made it possible to achieve a completely reproducible mode locking in ultrashort (20 psec) pulses, in agreement with the reciprocal of the spectral width. Absolute stabilization of the average emission frequency was also observed.