Independence of absorption coefficient-linewidth product to material system for multiple quantum wells with excitons from 850 nm to 1064 nm

The authors have measured the absorption coefficient ( alpha ) and linewidth ( Delta ) of the excitons of GaAs/AlGaAs and strain-balanced InGaAs/GaAsP multiple-quantum-well (MQW) modulators with wavelengths from 850 to 1064 nm. They find that alpha decreases and Delta increases as wavelength increases, but their product, and thus the integrated absorption coefficient, remains roughly constant. Thus, the reduced performance observed for longer wavelength modulators is due to exciton broadening.<>