Spontaneous emission into a planar optical waveguide mode by an atom   outside the waveguide
  An electronically excited atom or molecule located outside but near a planar optical waveguide can decay by spontaneous emission of a photon into a guided mode of the waveguide. We outline a QED theory for calculating the probability for this process and describe general physical insights from that theory. A couple of representative examples are discussed in detail. 
Andrei Modoran and Gregory Lafyatis