Gain, refractive index, and /spl alpha/-parameter in InGaAs-GaAs SQW broad-area lasers

Gain, refractive index, and the linewidth enhancement factor, or /spl alpha/-parameter, are measured in broad-area InGaAs-GaAs single-quantum-well semiconductor lasers using below-threshold amplified spontaneous emission spectra and a far-field filtering technique. The /spl alpha/ parameter is shown to increase dramatically with increasing carrier density and wavelength. Modes propagating in the transparent substrate of the lasers are shown to have a significant influence on the measured value of /spl alpha/.