A Quantum Electrodynamics Description of Quantum Coherence and Damping in Condensed-Phase Energy Transfer.

Quantum coherence in condensed-phase electronic resonance energy transfer (RET) is described within the context of quantum electrodynamics (QED) theory. Mediating dressed virtual photons (polaritons) are explicitly incorporated into the treatment, and coherence is understood within the context of interfering Feynman pathways connecting the initial and final states for the RET process. The model investigated is that of an oriented three-body donor, acceptor, and mediator RET system embedded within a dispersive and absorbing polarizable medium.

Nonlocalized Generation of Correlated Photon Pairs in Degenerate Down-Conversion.

The achievement of optimum conversion efficiency in conventional spontaneous parametric down-conversion requires consideration of quantum processes that entail multisite electrodynamic coupling, actively taking place within the conversion material. The physical mechanism, which operates through virtual photon propagation, provides for photon pairs to be emitted from spatially separated sites of photon interaction; occasionally pairs are produced in which each photon emerges from a different point in space. The extent of such nonlocalized generation is influenced by individual variations in both distance and phase correlation.

Hyper-Rayleigh scattering in centrosymmetric systems.

Hyper-Rayleigh scattering (HRS) is an incoherent mechanism for optical second harmonic generation. The frequency-doubled light that emerges from this mechanism is not emitted in a laser-like manner, in the forward direction; it is scattered in all directions. The underlying theory for this effect involves terms that are quadratic in the incident field and involves an even-order optical susceptibility (for a molecule, its associated hyperpolarizability).

Resonance energy transfer: influence of neighboring matter absorbing in the wavelength region of the acceptor.

In many of the materials and systems in which resonance energy transfer occurs, the individual chromophores are embedded within a superstructure of significantly different chemical composition. In accounting for the influence of the surrounding matter, the simplest and most widely used representation is commonly cast in terms of a dependence on local refractive index. However, such a depiction is a significant oversimplification, as it fails to register the electronic and local geometric effects of material specifically in the vicinity of the chromophores undergoing energy transfer.