Investigation of biexciton induced linear and nonlinear refractive index changes in ellipsoidal quantum dot

The biexciton states of the ground and excited levels in a GaAs strongly oblate ellipsoidal quantum dot are studied in the framework of the variational method. The trial variational wave function of the biexciton is constructed on the basis of single-particle wave functions, obtained in the scope of the adiabatic approximation. The biexciton energies for both ground and excited levels as a function of the ellipsoidal quantum dot's small semiaxis are obtained. The linear and nonlinear refractive indexes of the biexciton around one- and two photon resonances are calculated as real parts of the first- and third-order nonlinear susceptibilities, respectively. The spectra of changes of the biexciton refractive index for transitions between ground states as a function of the photon energy are obtained for different values of the small semiaxis of the ellipsoidal quantum dot