(3) Coherent preparation by laser light of quantum states of atoms and molecules can lead to quantum interference between the excitation pathways that control the optical response of the atoms and molecules. One consequence results in destructive quantum interference that can make the optically opaque materials transparent at the resonant frequency of a transition. This is termed electromagnetically induced transparency (EIT). The importance of EIT stems from the fact that it gives rise to greatly enhance the nonlinear optical processes in the spectral region of induced transparency of the medium.
One of our on going research is focused on using EIT to study the properties of nonclassical light, which is usually achieved from the nonlinear optical process such as SPDC. However, low generation efficiency and phase matching requirement hinder the applications of SPDC. Enhancement of optical nonlinearities near atomic resonances is already well known. Unfortunately, attempts to use this resonance enhancement have been frustrated by problems associated with resonant absorption, phase shifts, and unwanted nonlinearities such as self-focusing and beam distortion. Atomic coherence effects such as EIT cannot only further enhance the nonlinearities but reduce these problems. We wish to obtain strong nonclassical light sources based on EIT systems. Recently both theories and experiments have been carried out to improve the nonlinearities near resonance by atomic coherence effects. Stimulated by this motivation, we are trying to formulate the nonlinear optical processes in the three-dimensional model and
looking at some new phenomena and applications, especially the generation of Stokes and anti-Stokes from an EIT atomic gas. In addition, almost theories are based on one-dimensional model to characterize the interaction between light and matter. This is insufficient to describe problems such as imaging. In such a case, a three-dimensional model is desired to study the transverse effects.
(4) SPDC has been used extensively at UMBC to the study fundamental aspects of quantum theory and new kinds of imaging (‘Ghost’ Imaging and 'Ghost' Interference effects. These experiments are usually performed with very low efficiency SPDC in order to avoid noise effects and ensure that the source gives out only pairs of entangled photons. We have been interested in theoretically studying the high efficiency regime of SPDC or parametric amplification. The precise nature of noise in ‘Ghost’ imaging and interference due to high efficiency SPDC, along with experimental limitations leads us to certain experimental precautions required to reproduce these effects on a macroscopic scale.
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Quantum Optics Group
