In this paper, we present an accurate and computationally efficient system-level optical propagation technique suitable for the modeling of optical interfaces. Our technique is based on extensions to the angular spectrum technique used to solve the Rayleigh-Sommerfeld formulation. By using a FFT, the angular spectrum technique is efficient and suitable for system-level modeling of the complete system. To support the reflection and transmission at optical interfaces, we implement a semi-vector technique, taking into account the polarization of the optical wavefront. The polarization is used to determine the reflection and transmission coefficients through the use of Berreman's 4×4 matrix. Solutions are provided for typical TE and TM waves, however, wavefronts with arbitrary linear polarization are also supported. In this paper, we present a system-level simulation of a Silicon on Sapphire (SOS) interface.