Ultrashort pulse generation from a Q-switched AlGaAs laser with cw injection

Injection of a weak cw radiation in a Q-switched AlGaAs laser diode is shown to produce single-mode pulses with a quasi-linear downchirp of very large amplitude. Strong pulse compression can be achieved by using single-mode dispersive fibers at the laser output. Time-resolved spectroscopic measurements of the laser pulses are presented. Optical solitary pulses shorter than 2 ps are obtained after compression, which corresponds to a pulse compression factor larger than 15. Although the laser-fiber coupling is not fully optimized, peak powers exceeding 3 W are measured at the fiber output. These performances are believed to be the best ever reported for an electrically pumped Q-switched AlGaAs laser diode.