It is shown that by adapting the refractive indexes in the vicinity of interfaces, the 2-D beam propagation method based on the finite-difference (FDBPM) scheme can be made much more effective. This holds especially for TM modes propagating in structures with high-index contrasts, such as surface polaritons. A short discussion is given on the applicability of the FDBPM.
Hoekstra, H., Krijnen, G. J. M., & Lambeck, P. (1992). Efficient interface conditions for the finite difference beam propagation method. Journal of lightwave technology, 10(3), 1352-1355. https://doi.org/10.1109/50.166775