BREAKUP OF CW MULTIMODE OSCILLATIONS AND LOW-FREQUENCY INSTABILITY INA MICROCHIP SOLID-STATE LASER BY HIGH-DENSITY PUMPING

The effect of high-density pumping on lasing mode spectra is investiga ted in a laser-diode pumped microchip LiNdP4O12, (LNP) laser. Breakup of multimode oscillations, leading to single-mode oscillations, is obs erved experimentally. It is shown analytically that the enhanced Auger recombination process among excited Nd ion pairs results in a strong deformation of spatial hole-burning patterns, leading to a destabiliza tion of the multimode laser output via a quadratic-to-quartic transiti on of the spatial distribution of population inversion. The destabiliz ation threshold is shown to be given by a universal relation which rep roduces experimental results quite well. A mode-partition instability is observed above the transition, whose properties are intimately rela ted to the antiphase dynamics.