SUB-POISSONIAN PROCESSES IN QUANTUM OPTICS

The author reviews methods for generating sub-Poissonian light and rel ated concepts. This light has energy fluctuations reduced below the le vel which corresponds to a classical Poissonian process (shot-noise le vel). After an introduction to the concept of nonclassical light, an o verview is given of the main methods of quantum-noise reduction. Sub-P oissonian processes are exemplified in different areas of optics, rang ing from single-atom resonance fluorescence to nonlinear optics, laser physics, and cavity quantum electrodynamics. Emphasis is placed on th e conceptual foundations, and on developments in laser theory that lea d to the possibility, already demonstrated experimentally, of linewidt h narrowing and sub-Poissonian light generation in lasers and masers. The sources of quantum noise in these devices are analyzed, and four n oise-suppression methods are discussed in detail: regularization of th e pumping, suppression of spontaneous-emission noise, nonadiabatic evo lution of the atomic variables, and twin-beam generation.