PHASE-AMPLITUDE COUPLING FACTOR OF LASER-DIODES WITH SATURABLE ABSORBER

The phase-amplitude coupling factor (alpha-factor) is one of the fundamental parameters of semiconductor lasers. We show that this factor can be evaluated by time-resolved spectroscopic measurements in pulsed regime. Experiments are carried out with injection-seeded single-mode GaAs lasers whose active stripe includes regions of saturable absorption made by ion implantation. We show that the measured pulse downchirp is proportional to pulse energy. The downchirp amplitude is found to approach four laser cavity intermode spacings at the highest energies. Correspondingly, the alpha-values can be five times higher than those reported to date in litterature. High alpha-values are confirmed in pulse compression experiments. Several mechanisms are proposed to interprete these new results.