The linear and the third-order nonlinear optical absorption coefficient and refractive index changes of a hydrogenic impurity in an ellipsoidal quantum dot have been investigated, using the compact-density matrix formalism and an iterative method. In this regard, the effect of the size and geometry of the dot, aluminium concentration in Ga Lambda s/Lambda l(x)Ga(1-x)As structures, and optical intensity on the optical absorption coefficient and refractive index changes are investigated. It is found that the light intensity, size and geometry of the dot and aluminium concentration have a great influence on the absorption coefficient and refractive index changes of the dot. (C) 2010 Elsevier B. V. All rights reserved.