Research interests are in the areas of quantum optics, nonlinear optics, and laser physics. We are studying the fundamental nature of light and its interaction with atoms. Light beams produced by an incandescent bulb, a laser, and an atom are different. An understanding of this difference requires use of the quantum theory of light. These studies of quantum effects are important not only fundamentally but also have potential applications in atomic spectroscopy, optical precision measurements, optical computing, optical storage, and optical communication.

We have been studying the properties of nonclassical states generated by nonlinear optical processes such as second harmonic generation, four-wave mixing, and optical parametric oscillation. Many of these states have been experimentally realized. We have developed new techniques to study the statistical properties of these nonclassical states. An analytic calculation based on this approach for homodyne detection of light from a parametric oscillator has revealed a rich variety of quantum effects displayed by this light. Examples of these quantum effects include antibunching, subPoisonian statistics, and novel nonclassical correlations, which are dramatic manifestations of quantum interference and collapse of the wave function.

Interaction of these nonclassical states with simple atomic systems allows us to explore regimes which from the start have no classical analogs. The atom can be in free space or inside an optical cavity. There can be dissipation due to atomic and cavity decays. Our aim is to understand how the quantum nature of the atom-field interaction is reflected in the fluctuation and correlation properties of the scattered light. Practical applications of these will be in microlasers, which will play an important role in the next generation of highly efficient miniature devices and communications.

We are also investigating squeezing effects associated with the mechanical motion of an atom trapped in time dependent fields. We find that in Paul Trap, depending on the strength of magnetic field, the position or momentum quadrature is squeezed. We find regions of instability where the variances of both quadratures continue to grow with time. Since an important purpose of trapping atoms is to minimize the center of mass motion, these studies will provide a better understanding of any fundamental limits on the residual particle motion.