Direct and indirect intraband optical absorption due to carrier transitionsfrom discrete levels to continuum states in quantum dot system

Within the framework of perturbation theory, a model is presented to calculate the direct andindirect intraband opticalabsorption cross-section due to carrier transitions from thequantum dot(QD) level to thecontinuum states. The results indicate that the phonon-assisted transition processdominates the total intraband optical transition process for large photon energies, and that theamplitude of the absorption cross-section for the indirect process is temperaturedependent, while it is dependent upon the QD size for the direct process. Our theoretical model mayprove useful for improving the performance of optoelectronic devices based onQD lasers oramplifiers.