GAIN SATURATION PROPERTIES OF A SEMICONDUCTOR GAIN MEDIUM WITH TENSILE AND COMPRESSIVE STRAIN QUANTUM-WELLS

Gain saturation properties of a multiple-quantumwell structure with bo th tensile and compressively strained quantum wells are investigated a nalytically. This type of structure has recently been experimentally d emonstrated to serve as a basis for the implementation of a two-polari zation/two-frequency laser and polarization insensitive traveling wave (TW) amplifier. The performance of these devices strongly depends on t he interaction between the TE and TM gains of the structure. The gain medium model appropriate for this type of structure is developed and t he rate equation approach is used to describe the saturation propertie s of TE/TM gains and the coupling between the TE and TM gains due to g ain saturation. The minimum amount of coupling between the two is gove rned by the basic symmetry of the light-hole wavefunction which intera cts with photons of both polarization: photon cross-coupling. The fini te rate of carrier escape from the quantum wells provides for carrier induced coupling between the populations of the two well types and the refore also couples TE and TM gains: carrier cross-coupling. The perfo rmance of a polarization insensitive amplifier, laser, and polarizatio n control element is evaluated as a function of the amount of carrier cross-coupling, which is a structure dependent parameter. A structure with high degree of cross-coupling is desirable for polarization insen sitive TW amplifier, while two-polarization lasers and polarization co ntrol elements require minimum cross-coupling.