Multimode operation and mode-locking effect in injection lasers

The oscillation regime of GaAs injection lasers has been investigated by methods of time-resolved spectroscopy and nonlinear interferometry. The relative roles of random and correlated process were studied. Spectroscopic data and interferometric investigations of laser samples in CW as well as in pulse regimes show that in most cases multimode operation occurs with random phase fluctuations. However, in some cases signs of mode locking of longitudinal modes were observed with ultrashort pulsation. The duration time of the pulsation is estimated to be about 3 ps.