Polarization insensitive electro-absorption and gain-switching quantum-well modulators using interdiffusion

A theoretical study of the polarization independent quantum-well gain using interdiffusion is presented here. Group V sublattice interdiffusion in InGaAs/InP quantum wells is used to produce polarization independent optical gain. The reverse bias and carrier effects on the subband structures, transition energy and optical gain of the interdiffused quantum well are discussed. The interdiffused quantum well structures are optimized in terms of their subband structure, carrier density, structural parameters and properties of optical gain spectra. The results show that an optimized interdiffused quantum well structure can produce polarization independent optical gain over a range of operation wavelengths around 1.5 mu m, although the differential gain and linewidth enhancement factor are slightly degraded. The required tensile strain for the polarization independence of a lattice-matched quantum well structure is generated here using interdiffusion. These results suggest that polarization independent optical devices can be fabricated using interdiffusion using a lattice-matched InGaAsP quantum well structure.