Background reading: http://en.wikipedia.org/wiki/Finite-difference_time-domain_method
Our group has a license for Lumerical FDTD simulations.
A license server is available for Lumerical, at gallumbits.eng.gla.ac.uk swansea.eng-ad.gla.ac.uk port 8095 which uses the license manager available in more recent versions of Lumerical FDTD Solutions. It it also possible to run the simulations on the Device Modelling Group's computation cluster, Miffy. Access to this can be obtained by emailing Engineering IT support.