Modified angular spectrum of plane waves method by adding perfectly matched layers to eliminate aliasing

We propose a method to add Perfectly Matched Layers (PMLs) at the lateral sides of the computational domain by complex coordinate transformation. It modifies the Helmholtz equation from which the rigorous numerical solution for the Angular Spectrum of Plane Waves (ASPW) method could be obtained. The results of the numerical experiments are compared with the traditional ASPW. They are in nice agreement. The numerical effort is also discussed in different cases. It is showed that the modified ASPW method performs well when simulating highly divergent beams and evanescent waves.