Meep (or MEEP) is a free finite-difference time-domain (FDTD) simulation software package developed at MIT to model electromagnetic systems, along with our MPB eigenmode package. Its features include:
-Free software under the GNU GPL.
-Simulation in 1d, 2d, 3d, and cylindrical coordinates.
-Distributed memory parallelism on any system supporting the MPI standard. Portable to any Unix-like system (GNU/Linux is fine).
-Arbitrary anisotropic electric permittivity ε and magnetic permeability μ, along with dispersive ε(ω) and μ(ω) (including loss/gain) and nonlinear (Kerr & Pockels) dielectric and magnetic materials, and electric/magnetic conductivities σ.
-PML absorbing boundaries and/or perfect conductor and/or Bloch-periodic boundary conditions.
-Complete scriptability — either via a Scheme
scripting front-end (as in libctl and MPB), or callable as a C++ library; a Python interface is also available.
and ...
link: http://ab-initio.mit.edu/wiki/index.php/Meep