In the present work, a nonlinear dielectric function is derived using the B
orn-Huang equation and taking into account dispersion of optical phonons an
d nonlinear terms in the polarization vector P(u, E). The theoretical resul
ts show an obvious shift of the profile of the dielectric function. The sam
e expressions for the linear dielectric functions as previous ones are also
obtained when nonlinear factors are set to be zero in the present formulae
. (C) 2000 Published by Elsevier Science B.V.