A Quantum Electrodynamical Theory of Differential Scattering Based on a Model with Two Chromophores. II. Differential Raman Scattering of Circularly Polarized Light

Chiral systems can scatter circularly polarized photons at rates dependent on the handedness of the incident radiation. Differential intensities of Raman scattering by optically active organic molecules have been observed recently. The present work deals with the theory of both Rayleigh and Raman differential scattering by using quantum electrodynamics. The calculations of differential intensities are based on a two-chromophore model in which the chromophores, assumed to be achiral in isolation, become optically active due to their dissymmetric arrangement. Results are reported for both ‘in-plane’ and ‘out-of-plane’ polarizations of the scattered radiation. They apply to an arbitrary scattering geometry and group separation. The limiting near- and far-zone behaviour is analysed in detail. In this paper (part I), the basic theory common to Rayleigh and Raman differential scattering is presented and is then applied to the Rayleigh process. The application to the Raman process is given in part II. In the Rayleigh case, the dominant contribution to the differential effect arises from interference of second-order probability amplitudes. This term varies linearly with the inter-chromophore separation in the near-zone, but inversely in the far-zone. Higher-order corrections to the differential intensities involve coupling between the chromophores; the leading correction, involving the interference of the second- and fourth-order amplitudes, has been computed

Translational Entanglement of Dipole-Dipole Interacting Atoms in Optical Lattices

We propose and investigate a realization of the position- and momentum-correlated Einstein-Podolsky-Rosen (EPR) states [Phys. Rev. 47, 777 (1935)] that have hitherto eluded detection. The realization involves atom pairs that are confined to adjacent sites of two mutually shifted optical lattices and are entangled via laser-induced dipole-dipole interactions. The EPR "paradox" with translational variables is then modified by lattice-diffraction effects, and can be verified to a high degree of accuracy in this scheme.Comment: 4 pages, 3 figures, to be published in PR

Effect of superradiance on transport of diffusing photons in cold atomic gases

We show that in atomic gases cooperative effects like superradiance and subradiance lead to a potential between two atoms that decays like $1/r$. In the case of superradiance, this potential is attractive for close enough atoms and can be interpreted as a coherent mesoscopic effect. The contribution of superradiant pairs to multiple scattering properties of a dilute gas, such as photon elastic mean free path and group velocity, is significantly different from that of independent atoms. We discuss the conditions under which these effects may be observed and compare our results to recent experiments on photon transport in cold atomic gases.Comment: 4 pages and 1 figur

Collapse of optical binding under secondary irradiation

When an optically trapped and bound micrometer-sized chain of particles is subjected to a suitably oriented secondary laser beam above a threshold level of intensity, the structure will collapse. The effect arises from modifications to the interparticle energy landscapes owing to the superposition of optically induced potentials. From the theory it also emerges that, for particles separated by near-field distances, optically induced assemblies may be continuously transformed between linear, spherical, and lamellar forms. The results show scope for the optical fabrication of moldable nanoscale structures