Reciprocity and the scattering matrix of waveguide modes
arXiv:1301.2458 · doi:10.1103/PhysRevA.87.013838
Abstract
The implications of the Lorentz reciprocity theorem for a scatterer connected to waveguides with arbitrary modes, including degenerate, evanescent, and complex modes, are discussed. In general it turns out that a matrix is symmetric, where is the matrix of generalized orthogonality coefficients, and is the scattering matrix. Examples are given, including a scatterer surrounded by waveguides or free space, and discontinuities of waveguides.