Master Equations and Sources II

Abstract

A cavity mode driven by thermal light does not provide a very interesting example of an optical source. Indeed, it is not really a source at all since the total field observed at the output of the cavity is just the thermal field that drives the cavity. It is only for a non-thermal-equilibrium system that we will see a bright light, different from the surroundings, emitted by a source. The importance of the cavity mode calculation is that it provides one of the building blocks that we will use to construct more interesting sources. At the end of this lecture we will meet some examples of more interesting photoemissive sources. But first, most of the lecture will be devoted to a discussion of two-state atoms which provide another building block for the construction of more interesting sources. Excited atoms act as a source of radiation through spontaneous and stimulated emission. We are going to use the master equation approach from Sect. 1.2 to treat these processes for an atom in thermal equilibrium.