The MIT Photonic-Bands (MPB) package is a free program for computing the band
structures (dispersion relations) and electromagnetic modes of periodic
dielectric structures, on both serial and parallel computers. It was developed
by Steven G. Johnson at MIT in the Joannopoulos Ab Initio Physics group.

This program computes definite-frequency eigenstates of Maxwell's equations in
periodic dielectric structures for arbitrary wavevectors, using fully-vectorial
and three-dimensional methods. It is especially designed for the study of
photonic crystals (a.k.a. photonic band-gap materials), but is also applicable
to many other problems in optics, such as waveguides and resonator systems.
(For example, it can solve for the modes of waveguides with arbitrary cross-
sections.)

WWW: http://ab-initio.mit.edu/mpb/