Theory of Coherence and Photon Statistics of Classical and Nonclassical Light on a Microscopic Basis

Abstract

In this chapter, we present a theory of macroscopic light fields based on the superposition of non-stationary elementary waves emitted at random space-time points [Teich et al. (1984)]. In this way, we can construct optical fields of all kinds, such as macroscopic optical fields which are sub-Poissonian, Poissonian, and superPoissonian, including those which are Gaussian (chaotic) and super-Gaussian (superchaotic). This makes it possible for us to follow the effect of the statistics of primary excitations and of individual emissions in photon statistics and coherence of macroscopic optical fields. Of course, in the limit of a very high number of independent elementary emissions, we arrive at the Gaussian optical field. Further, we will show the influence of feedback on photon statistics in optical interactions. Many optical fields with such a broad spectrum of photon statistics can be classified in terms of the generalized superposition of coherent fields and quantum noise, based on the properties of the generating function (8.59b), which also will be discussed in greater detail in this chapter. The generalized superposition of coherent fields and quantum noise provides a good way for understanding relations between various quantum features of light, such as the squeezing of vacuum fluctuations, antibunching of photons, and sub-Poisson photon statistics. We also mention a more general definition of the squeezing of vacuum fluctuations, called the principal squeezing and show some possibilities for the use of entropy as a global quantity to characterize optical fields, including nonclassical optical fields.