  In the new approach to study the optical response of periodic structures,
successfully applied to study the optical properties of blue-emitting InGaN/GaN
superlattices, the spontaneous charge polarization was neglected. To search the
effect of this quantum confined Stark phenomenon we study the optical response,
assuming parabolic band edge modulations in the conduction and valence bands.
We discuss the consequences on the eigenfunction symmetries and the ensuing
optical transition selection rules. Using the new approach in the WKB
approximation of the finite periodic systems theory, we determine the energy
eigenvalues, their corresponding eigenfunctions and the subband structures in
the conduction and valence bands. We calculate the photoluminescence as a
function of the charge localization strength, and compare with the experimental
result. We show that for subbands close to the barrier edge the optical
response and the surface states are sensitive to charge polarization strength.
