Subpicosecond switch-off and switch-on of a semiconductor laser due to transient hot carrier effects

Recently it has been shown that perturbation of an already operating semiconductor laser with an additional pump pulse may lead to an unusual ultrafast switch-off. This effect is due to transient carrier heating. Subsequent carrier cooling allows for switch-on after about two picoseconds. In vertical cavity lasers containing only a few quantum wells as the active medium, the recovery, however, is limited by the comparatively low gain in the cavity. Here we demonstrate experimentally that both switch-off and switch-on can exhibit subpicosecond time constants if a bulk semiconductor is used as the active medium.