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Manuscript Title: A program for calculating photonic band structures and Green's functions using a non-orthogonal FDTD method.
Authors: A.J. Ward, J.B. Pendry
Program title: ONYX
Catalogue identifier: ADIJ_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 112(1998)23
Programming language: Fortran.
Computer: Digital Alpha 250.
Operating system: Digital UNIX V3.2D-1 (Rev. 41), MS-DOS.
RAM: 8.4M words
Word size: 32
Keywords: Electrostatics, Discretised maxwell's Equations, Order(n) method, Finite difference time, Domain (fdtd) method, Photonic band structure, Green's function, Density of states.
Classification: 10.

Nature of problem:
Efficient calculation of either photonic dispersion relationships or Green's functions for photons in complex dielectric structures.

Solution method:
A discretisation of Maxwell's equations in both the space and time domains which leads to finite difference equations connecting the electric and magnetic fields at one time step to those at the next. After using these equations to find the response in the time domain to a particular initial set of fields, we perform a Fourier transform to obtain the response in the frequency domain. From this we can easily extract dispersion relationship information, or alternatively, by setting the initial fields to be a delta function, we can obtain the Green's function for the system under consideration.

The complexity of the dielectric structure that the method can be applied to is limited only by the computer time and memory available. Both time and memory requirements scale linearly with the system size. One restriction on the method is that the dielectric permittivity and magnetic permeability must both be independent of frequency. This means it cannot treat some problems typically those involving metals.

Unusual features:
Option to work with non-orthogonal co-ordinate systems.

Running time:
Highly dependent on the system under consideration. For the test band structure calculation given, 164 seconds on a Digital Alpha 250 workstation.