(a) (b)Figure 11: a) Density of states for photons in one dimension in a material in terms ofω; b) Density
of states of photons for voids in an fcc lattice
5.6 Photon Density of States
Now we have a three-dimensional density of states calculated for an fcc crystal. There are holes in
some material and the holes have an fcc lattice. The material has a dielectric constant of 3, the holes
have 1 (looks like some kind of organic material). So we have a lot of holes in the material, a large
modulation and we calculate the density of states. The little line in fig. 11(b) is the vacuum density of
states. But we have this periodic modulation and when there is a band we can get a gap. The peaks
are typically near edges and near the gaps because there the states pile up.
If we have a strange function for the density of states and we want to calculate the corresponding
planck radiation law, we just have to plug it in because the planck radiation law is the energy times
the density of states times the Bose-Einstein factor (see chapter 4).