The change of the refractive index due to quantum well (QW) disordering is calculated for light propagating normal to the AI0.3Ga0.7As/GaAs QW layers (i.e. along the QW growth direction). A hyperbolic function is used to model the above QW confinement profile after disordering, i.e. thermal interdiffusion of trivalent atoms across the wellbarrier interfaces. The refractive index difference (An) is evaluated for two cases, where case I refers to the difference between a partially disordered QW and a more extensively disordered QW, while case II refers to the difference between an as-grown QW and a partially disordered QW. The results demonstrate that good photon confinement (large An > 0) can be achieved for both cases, where An increases with increasing QW width and decreases with annealing time for case I while for case II it increases with annealing time. In comparing the two cases, a shorter annealing time is required to achieve the same value of An if the case II structures are used. The change of refractive index obtained here demonstrates a larger value of An than that produced by the variation of the concentration of free carriers in the bulk material.