Theory of optical spontaneous emission rates in layered structures

This paper presents expressions for the optical power and fields radiated by an oscillating dipole in layered structures, with loss or gain, that are easy to evaluate. For structures without loss or gain, it is discussed that the radiated power is a direct measure for the local density of modes, whereas for structures with loss or gain, this correspondence no longer holds due to interaction between the dipole and evanescent modes. The presented theory is illustrated with a number of examples.