title: Parabasal thin-element approximation approach for the analysis of microstructured interfaces and freeform surfaces.
abstract: The thin-element approximation (TEA) approach is an efficient algorithm to analyze microstructured interfaces, e.g., diffractive optical elements or scattering surfaces. However, the classical approach is valid only under the condition of paraxial illumination. We hereby develop an extended algorithm to include parabasal illumination, which is characterized by low divergence with arbitrary propagation direction. The extended approach is named as the parabasal TEA approach. In this paper, we present the algorithm of the parabasal TEA approach and compare the results with that of a rigorous calculation in order to demonstrate its validity. We also discuss the role of the parabasal TEA approach in a more general concept for modeling light propagating through freeform surfaces.
authors.forename: Huiying
authors.initials: H
authors.lastname: Zhong
authors.forename: Site
authors.initials: S
authors.lastname: Zhang
authors.forename: Frank
authors.initials: F
authors.lastname: Wyrowski