Efficient absorbing layers for the guided-mode analysis using the imaginary-distance BPM

摘要

The imaginary-distance beam-propagation method (ID-BPM) with the conventional perfectly matched layer (PML) often yields unstable results for the guided-mode analysis of an optical waveguide. To address this issue, two efficient absorbing layers are discussed on the basis of suitable modifications to the stretching coordinate variables of the conventional PML. Theoretical descriptions of these layers are presented using the plane wave solutions. The performance of these layers is investigated for several two- and three-dimensional problems. It is found for the analysis of a light-guiding metal line near the cutoff condition that the calculation time is reduced to one sixth of that using a zero boundary.