Optical gain and refractive index of a laser amplifier in the presence of pump light for cross-gain and cross-phase modulation

The wavelength dependent changes in optical gain and refractive index in a Fabry-Perot semiconductor optical amplifier are measured for various detunings of the pump wavelength from the quasi-Fermi level separation. The refractive index change is nearly constant over a very large wavelength range. We also present data for the linewidth enhancement factor due to optical injection. Estimates of the carrier densities and stimulated recombination rates are made using our optical gain model based on realistic band structure calculations for a strained quantum-well laser. Our results are very useful for ultra-broad-band wavelength conversion by cross-gain and cross-phase modulation (XGM, XPM).