An efficient way to compare ABCs

The authors present a performance comparison of absorbing-boundary conditions (ABCs), including the introduced perfectly matched layer (PML), for finite-difference time-domain (FDTD) simulations. This innovative PML for truncating FDTD domains was introduced by J. Berenger (see J. Comp. Phys. vol.114, p.195-200, 1994), and has since been the subject of intensive study. The key feature of the PML is its extremely low reflectivity over a broad range of (real) incidence angles, and its broadband characteristics. The authors provide color-coded graphs, which can be easily used to measure the PML´s performance as a function of frequency and incidence angle. An important component of these graphs is that they also display the performance of the PML for evanescent waves. For comparison, similar graphs are given for the second order Mur and Lindman (see J. Comp. Phys., vol.18, p.66-78) ABCs. The superior performance of the PML (for propagating) waves is clearly seen, but for evanescent waves, the Lindman ABC gives better performance