  In the field of neutrino astronomy, large volumes of optically transparent
matter like glacial ice, lake water, or deep ocean water are used as detector
media. Elementary particle interactions are studied using in situ detectors
recording time distributions and fluxes of the faint photon fields of Cherenkov
radiation generated by ultra-relativistic charged particles, typically muons or
electrons.
  The Photonics software package was developed to determine photon flux and
time distributions throughout a volume containing a light source through Monte
Carlo simulation. Photons are propagated and time distributions are recorded
throughout a cellular grid constituting the simulation volume, and Mie
scattering and absorption are realised using wavelength and position dependent
parameterisations. The photon tracking results are stored in binary tables for
transparent access through ANSI-C and C++ interfaces. For higher-level physics
applications, like simulation or reconstruction of particle events, it is then
possible to quickly acquire the light yield and time distributions for a
pre-specified set of light source and detector properties and geometries
without real-time photon propagation.
  In this paper the Photonics light propagation routines and methodology are
presented and applied to the IceCube and Antares neutrino telescopes. The way
in which inhomogeneities of the Antarctic glacial ice distort the signatures of
elementary particle interactions, and how Photonics can be used to account for
these effects, is described.
