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 vari ous detunings of the pump wavelength from the quasi-Fermi level separa tion. 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 an d 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 waveleng th conversion by cross-gain and cross-phase modulation (XGM, XPM).