ULTRAFAST ABSORBER SATURATION PROCESS AND SHORT-PULSE FORMATION IN INJECTION-LASERS

The nature of lasing threshold in passively Q-switched GaAs/AlGaAs las ers with saturable absorbers formed by heavy ion implantation is inves tigated in this article. After studying various laser characteristics, including threshold current density, differential quantum efficiency, spectral output, and picosecond time-resolved emission, we conclude t hat the origin of the Q-switching is unlikely to be caused by spontane ous emission or mode locking, and that collective coherent radiation e ffects may contribute to the onset of lasing. (C) 1998 American Instit ute of Physics. [S0021-8979(98)03422-7].