We apply two- and three-dimensional numerical calculations to study optical nanoantennae made of two coupled gold nanostructures, enclosing a single emitter in their gap. We show that, using structures manufacturable with today's nanotechnology, it is possible to increase the radiative decay rate by three orders of magnitude while keeping a quantum efficiency larger than 80% in the near-infrared regime. We examine the competition between the radiative and nonradiative processes in the presence of the antennae as a function of wavelength and antenna geometry. Our results hold great promise for improving the quantum efficiency of poor emitters such as silicon nanocrystals or carbon nanotubes.

W e te s t th e th re e -d im e n s io n a l fin ite -d iffe re n c e tim e -d o m a in m e th o d fo r th e c a lc u la tio n of d e ca y rates of a n e m itte r p la ce d in c lo s e v ic in ity to m e ta l n a n o stru ctu re s. B y ch o o s in g a n a ly tic a l so lva b le syste m s w e a sse s its a c c u ra c y and in d ic a te th e issu e s d e rivin g fro m n e a r-fie ld co u p lin g , O h m ic losses and sta irca sin g . T h e la tte r is fo u n d to b e th e m o s t p ro b le m a tic one, b e c a u s e it g ive s rise to spurious p e a ks th a t s u rv iv e even fo r v e ry fin e discre tiza tio n s.Keywords: D e ca y R ates, C o m p u ta tio n a l E le ctro d yn a m ics, FDTD, M e ta l N a n o stru ctu re s, P la sm o n R eso n an ce s.

We investigate the properties of finite gold nanocones as optical antennas for enhancing molecular fluorescence. We compute the modification of the excitation rate, spontaneous emission rate, and quantum efficiency as a function of the nanocone base and length, showing that the maximum field and fluorescence enhancements do not occur for the same nanocone parameters. We compare the results with those for nanorods and nanospheroids and find that nanocones perform better.

We study experimentally superradiant Rayleigh scattering from a Bose-Einstein condensate (BEC) in a new parameter regime where pump depletion and the exchange of photons between the endfire modes are important. Through experiments and simulations we show that collective atom light coupling leads to the self-organized formation of dynamic Bragg gratings within the sample. These gratings lead to an efficient back-scattering of pump photons and optical resonator structures within the BEC.PACS numbers: 03.75. Nt,37.10.Vz,42.50.Gy With its extremely high optical depth and unique coherence properties, a Bose Einstein condensate provides an ideal object on which to study collective light scattering with the goal of generating and probing light-atom correlations. Superradiant light scattering (SLS) from ultra-cold atomic ensembles has been recognized as a method to generate entangled atoms and photons due to the fact that the interaction Hamiltonian has the generic form of a parametric amplifier H ∝â †b † , where correlations based on momentum conservation arise in the case of Rayleigh scattering [1], and angular momentum in the case of Raman processes [2]. Entanglement in the ultra-low gain regime of such an interaction, when far less than one atom-photon excitation pair is generated on average, forms the basis for a quantum repeater [3] and has been studied extensively [4]. Here, we are interested in the high gain -superradiant -regime where the detection of entanglement requires in general the measurement of both the phase and amplitude of the light and matter waves at the sub-shot noise level. While this is typically hampered by the lack of an atomic analogue to homodyne detection of light, a recent proposal claims entanglement may be detected by just counting photons and atoms [5]. Nonetheless, the full dynamics of coupled matter and light waves where one does not place limitations on the depletion of either the condensate or input light, and where propagation effects are considered, remain important issues if such correlations and entanglement are to be made useful resources.To this end, we explore superradiant Rayleigh scattering from a trapped, cigar shaped BEC as the pump detuning is varied while the single particle scattering rate R is kept constant. In this way, we investigate the effect of the detuning of the pump beam in the process, and move between the case where the pump beam remains essentially undepleted by the scattering, to the situation where superradiant scattering is 'clamped' by a lack of photons in the pump beam. Crucial to these dynamics is the structure that builds up along the long axis of the condensate, demonstrating characteristics from 'Dicke' superradiance from extended samples [6,7,8], a fact recognized recently both experimentally [9, 10] and theoretically [11,12,13,14]. Contrary to most earlier experimental work on the subject [9,15,16, 17], we end-pump along * hilliard@nbi.dk the long axis with a beam mode-matched to the transverse cross-section of the BEC in order to optimize the...