Analysis of rib waveguides by a fourth-order accurate finite-difference beam-propagation method.

When a step index waveguide is analyzed by the finite-difference method, the treatment of the discontinuous refractive index profile is a problem. In this paper, while the boundary condition of the field is taken into account, the improved finite-difference equation in which the truncation error is reduced to the fourth order is combined with the alternate direction implicit solution method, formulating a three-dimensional beam propagation method with high computational efficiency. First, by means of the imaginary axis method, an eigenmode analysis of the rib waveguide is carried out so that the effectiveness and validity of the method are proven. Next, a beam propagation analysis is carried out for the rib waveguide taper. By taking into account the discontinuity location of the refractive index, the quantization error is found to be reduced. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 85(12): 20–29, 2002; Published online in Wiley InterScience (<URL>www.interscience.wiley.com</URL>). DOI 10.1002/ecjb.10061 [ABSTRACT FROM AUTHOR]