PMLC: A perfectly matched layer collimator and its applications to time and frequency domain numerical techniques

Several types of absorbing boundary conditions and simple matched absorbers, employed for mesh truncation in time and frequency domain numerical techniques (FDTD, FEM) work well for normally incident waves. However, their performance at other angles of incidence is often deemed unacceptable, motivating their replacement by perfectly matched layers. We propose a medium that can collimate incident waves, producing almost normally incident plane waves that can be readily absorbed even by a low order absorbing boundary condition such as Mur's. This perfectly matched layer collimator (PMLC) is a lossless, uniaxially anisotropic medium; its numerical implementation is much simpler than that of the conventional PML. Numerical results demonstrate the effectiveness of this medium as a means of rendering the performance of a first order absorbing boundary condition comparable to that of a PML.