A REFLECTIONLESS SPONGE LAYER ABSORBING BOUNDARY-CONDITION FOR THE SOLUTION OF MAXWELLS EQUATIONS WITH HIGH-ORDER STAGGERED FINITE-DIFFERENCE SCHEMES

We develop, implement, and demonstrate a reflectionless sponge layer f or truncating computational domains in which the time-dependent Maxwel l equations are discretized with high-order staggered nondissipative f inite difference schemes, The well-posedness of the Cauchy problem for the sponge layer equations is proved, and the stability and accuracy of their discretization is analyzed. With numerical experiments we com pare our approach to classical techniques for domain truncation that a re based on second-and third-order physically accurate local approxima tions of the true radiation condition. These experiments indicate that our sponge layer results in a greater than three orders of magnitude reduction of the lattice truncation error over that afforded by such c lassical techniques. We also show that our strongly well-posed sponge layer performs as well as the ill-posed split-field Berenger PML absor bing boundary condition. Being an unsplit-field approach, our sponge l ayer results in similar to 25% savings in computational effort over th at required by a split-field approach. (C) 1998 Academic Press.