  Collective electronic excitations "excitons" in planar optical lattices
exhibit strong modifications of the radiative damping rate and directional
emission pattern as compared to a single excited atom. Excitons for long wave
numbers and polarizations orthogonal to the lattice plane exhibit superradiance
with a very short life time and a tightly confined emission direction. For
shorter wavelength and in plane polarization they can posses a long life time,
which beyond a critical wave number tends to infinity. Those excitons thus
become metastable and decoupled from the free radiation field. They can store a
single energy quantum for a long time and transfer the excitation over long
distances. In general the spatial, polarization and frequency dependence of the
emission pattern can provide us with optical and electronic properties of
optical lattices.
