TIME-BANDWIDTH PRODUCT OF GAIN-SWITCHED IN0.2GA0.8AS GAAS MICROCAVITYLASERS/

We present the temporal and spectral evolution of stimulated emission from In0.2Ga0.8As/GaAs microcavity laser samples at 20 K after femtose cond optical excitation. Both, linewidth and chirp become smaller when the cavity resonance is at shorter wavelengths within the gain spectr um of the quantum well: The linewidth is reduced from Delta lambda = 0 .41 nm at 923 nm, where the threshold is lowest, to Delta lambda = 0.2 6 nm at 884 nm. Comparison with a phenomenological model yields linewi dth enhancement factors alpha of 2 and 5 for emission wavelengths of 8 84 and 925 nm, respectively. A time-bandwidth product of 0.68 is obtai ned at the shorter wavelength. (C) 1995 American Institute of Physics.