Truncated SPW Operator for High Accuracy Propagation of Non-Paraxial Fields

The spectrum of plane waves (SPW) operator models free space propagation of electromagnetic fields in a rigorous way. However, numerically it is only suitable for small propagation distances. In particular for non-paraxial fields the SPW technique is often not practical. On the other hand, the Fresnel propagation operator is numerically suitable for larger distances, but physically it uses a paraxial field approximation (divergence of a few degrees). Thus, in particular for non-paraxial fields there is a need for alternative techniques which combine high physical modeling accuracy with reduced numerical effort. In our talk we present a new technique, which combines the numerical advantages of the Fresnel operator with significantly higher modeling accuracy. To this end we truncate the higher order SPW propagation kernel in a suitable way to adjust the compromise between accuracy and numerical effort. The theory is discussed and demonstrated. It is shown, that the truncated SPW operator closes the gap between SPW and far field approximation. The software LightTrans VirtualLab(TM) provides the described truncated SPW technique and is used for the numerical examples that are shown.