Spectral dependence of differential gain, mode shift, and linewidth enhancement factor in a InGaAs-GaAs strained-layer single-quantum-well laser operated under high-injection conditions

Strained-layer quantum-well lasers, when operated at moderate injection levels, are known to exhibit a reduced linewidth enhancement factor, α, an important parameter in the design of semiconductor lasers. Under increased loss conditions, when spill-over of carriers into the barrier becomes significant, they can also be operated in a quasi-double-heterostructure mode at the barrier wavelength. Thus, by proper control of loss, lasing at different wavelengths is possible, at least in principle. An investigation has been carried out to determine explicitly the spectral dependence of the differential gain, spectral shift, and α of a narrow-stripe InGaAs-GaAs separate-confinement strained-layer single-quantum-well laser operated near the wavelength of the GaAs barrier under extremely high injection. Despite the carrier spill-over, α was found to be remarkably low, about 1.7 at the spectral gain peak (877 nm), which was also the lasing wavelength