The numerical scheme for solving the Helmholtz equation, based on the Lanczos orthogonalization scheme, is generalized so that it can be applied to media with space-dependent absorption or gain profiles.
© 1992 Optical Society of America
R. P. Ratowsky, J. A. Fleck, Jr., and M. D. Feit, "Accurate solution of the Helmholtz equation by Lanczos orthogonalization for media with loss or gain," Opt. Lett. 17, 10-12 (1992)