PHASE-AMPLITUDE COUPLING FACTOR OF SINGLE-MODE GAIN-SWITCHED INGAASP LASER-DIODES

The phase amplitude coupling factor (alpha-factor) of gain-switched InGaAsP laser diodes is deduced from chirp measurements. A tunable laser scheme allows us to obtain the wavelength dependence of alpha over approximately 40 nm. The alpha-values are found to be higher than those deduced from spontaneous emission spectra below threshold. We show that the difference is explained by the dependence of alpha with carrier density. Time-resolved measurements of spontaneous emission during pulse build-up reveal that the carrier density at maximum can be 1.5 times higher than the threshold carrier density. Experimental evolutions of alpha are well reproduced by calculations.