Second harmonic field generated in reflection by an inhomogeneous nonlinear polarization

The second harmonic field reflected at an interface by a spatially inhomogeneous nonlinear polarization is calculated. We show that, through the spatial derivative of the nonlinear polarization, this spatial profile adds a new term to the reflected field calculated by Bloembergen and Pershan for a homogeneous nonlinear medium. The amplitude and phase of the additional term strongly alter both the amplitude and phase of the reflected field. The importance of this effect is illustrated in some meaningful physical cases. (C) 1998 Elsevier Science B.V.