Polaron effect on the optical absorption and refractive index of an exciton in quantum dots

We have studied the optical absorption of an exciton and its refractive index in a disc-like quantum dot, taking into account of the confined longitudinal optical (LO) phonons. Calculations are performed in the framework of the effective-mass approximation using the compact density-matrix approach. With typical semiconducting GaAs materials, the linear, third-order nonlinear, total optical absorption coefficients and refractive index changes with and without considering the exciton-phonon interaction have been examined. By comparing the polaron effect of the two-electron quantum dot, it is found that the corrections due to the LO phonons on the optical absorption and refractive index are very important and cannot be ignored.