Analysis of optical elements with the local plane-interface approximation

The local plane-interface approximation (LPIA) is a method for propagating electromagnetic fields through the inhomogeneous regions (e.g., elements) o f an optical system. The LPIA is the superclass of all approximations that replace the usually curved optical interfaces with local tangential planes. Therefore the LPIA is restricted to smooth optical surfaces. A maximum rad ius of curvature of the optical interface of the order of a few wavelengths is a rough estimate for the validity of the LPIA. Two important approximat ion levels of the LPIA are the thin-element approximation (TEA) and a geome tric-optical version of the LPIA (LPIA(ray)). The latter combines the wave- optical propagation of an electromagnetic field in the homogeneous region o f an optical system with a ray-tracing step in the inhomogeneous region. We discuss the regions of validity of the LPIA in general and the approximati on levels LPIA(ray) and TEA in detail. (C) 2000 Optical Society of America OCIS codes: 350.4600, 050.1940, 120.5710, 050.1970, 350.3950.