Fourier Series-Based Bidirectional Propagation Algorithm With Adaptive Spatial Resolution

Recently we described the implementation of complex coordinate transformation as boundary conditions into a bidirectional eigenmode expansion propagation algorithm based on Fourier series expansion for modeling optical field distribution in waveguide devices. In this communication we report on the implementation of an additional coordinate transformation known as adaptive spatial resolution into this algorithm. It helps significantly reduce the number of expansion terms needed to reach required accuracy especially for photonics structures containing layers of very different thicknesses and/or optical properties, e.g., metal layers.