Maxwellian material-based absorbing boundary conditions for lossy media in 3-D

A two time-derivative Lorentz material (2TDLM), which has been shown previously to be the correct Maxwellian medium choice to match an absorbing layer to a lossy region, is extended here to a complete absorbing boundary condition (ABC) for three-dimensional (3-D) finite-difference time-domain (FDTD) simulators. The implementation of the lossy 2TDLM (L2TDLM) ABC is presented. It is shown that in contrast to the one-dimensional (1-D) and two-dimensional (2-D) versions, the full 3-D ABC requires a three time-derivative Lorentz material in the edge and corner regions to achieve a rigorous matching of the resulting Maxwellian absorbing layer to the lossy medium. The 3-D ABC implementation thus requires the introduction of an auxiliary field to handle the edge and corner regions to achieve a state-space form of the update equations in the ABC layers. Fully 3-D examples including pulsed dipole radiation and pulsed Gaussian beam propagation in lossless and lossy materials as well as pulse propagation along a microstrip over lossless and lossy materials are included to illustrate the effectiveness of the L2TDLM ABC.