2.5D quasi-axisymmetric finite difference frequency domain modeling

A new 2.5D quasi-axisymmetric Finite Difference Frequency Domain (FDFD) algorithm for sources with arbitrary locations and polarizations greatly extends strict 2D axisymmetric modeling which requires on-axis or azimuthally-symmetric source distributions. Field expansions in sinusoidal modes are required, so multiple discretized Helmholtz operators A(m) must be constructed and inverted for each mode index m. Although convergence of the background and total fields can be relatively slow, particularly in the vicinity of the ring sources used in the expansion, convergence of scattered fields is reasonably fast. Excellent agreement with both analytic solutions and existing 2D axisymmetric FDFD simulations is demonstrated.