Cylindrical 2D beam propagation method for optical structures maintaining a revolution symmetry

A cylindrical form of the finite difference beam propagation method (FD-BPM) is, for the first time, proposed to make easier the analysis of optical waveguide configurations for which the index profiles have a revolution symmetry and maintain an azimuthal symmetry of the field distribution. For these configurations the new 2D cylindrical FD-BPM requires a computation time shorter than that of the classical 3D Cartesian FD-BPM. Solutions are given to remove numerical difficulties occuring on the revolution axis. The proposed method is first applied, in association with the Wijnands's method, to solving the modes of two fibers with complicated index profile. It is also applied to studying the progressive transition between two different monomode fibers. (C) 1999 Academic Press.