Enhancement of photon antibunching by passive interferometry

Abstract

Photon antibunching in intracavity second-harmonic generation and intracavity atomic absorption inside a high-Q optical cavity is discussed. A linearized description of quantum dynamics in the weak-field limit is used because the system size, as characterized by the number of photons n0 needed to probe the nonlinearity of the system, is often quite large for realistic parameters. In both cases standard results are recalled that demonstrate that antibunching is a small effect given by g(2)(0)-1≊-1/n0 for large values of n0. We show that when higher-order terms that are usually ignored in linearized treatments are retained, g(2)(0) satisfies the lower bound g(2)(0)≥0 even for small values of n0. It is further shown that by employing a high-Q cavity to suppress the coherent part of the spectrum of field fluctuations, perfect antibunching can be achieved even for large systems. Conditions under which this is possible are derived and curves are presented to illustrate the behavior.