Light scattering by an oscillating dipole in a focused beam

The interaction between a focused beam and a single classical oscillating dipole or a two-level system located at the focal spot is investigated. In particular, the ratio of the scattered to incident power is studied in terms of the oscillator's scattering cross section and the effective focal area. Debye diffraction integrals are applied to calculate it and results are reported for a directional dipolar wave. Multipole expansion of the incident beam is then considered and the equivalence between this and the Debye diffraction approach is discussed. Finally, the phase change of the electric field upon the interaction with a single oscillator is studied.Comment: 9 pages, 6 figure

Memory in the Photon Statistics of Multilevel Quantum Systems

The statistics of photons emitted by single multilevel systems is investigated with emphasis on the nonrenewal characteristics of the photon-arrival times. We consider the correlation between consecutive interphoton times and present closed form expressions for the corresponding multiple moment analysis. Based on the moments a memory measure is proposed which provides an easy way of gaging the non-renewal statistics. Monte-Carlo simulations demonstrate that the experimental verification of non-renewal statistics is feasible.Comment: 5 pages, 3 figure

Scanning Near-Field Optical Coherent Spectroscopy of Single Molecules at 1.4 Kelvin

We present scanning near-field extinction spectra of single molecules embedded in a solid matrix. By varying the molecule-tip separation, we modify the line shape of the spectra, demonstrating the coherent nature of the interaction between the incident laser light and the excited state of the molecule. We compare the measured data with the outcome of numerical calculations and find a very good agreement.Comment: 3 pages, 5 figures, submitted to Optics Letter

Metal nanoparticles in strongly confined beams: transmission, reflection and absorption

We investigate the interaction of tightly focused light with the surface-plasmon-polariton resonances of metal nanospheres. In particular, we compute the scattering and absorption ratios as well as transmission and reflection coefficients. Inspired by our previous work in Ref. [1], we discuss how well a metal nanoparticle approximates a point-like dipolar radiator. We find that a 100 nm silver nanosphere is very close to such an ideal oscillator. Our results have immediate implications for single nanoparticle spectroscopy and microscopy as well as plasmonics.Comment: 6 pages, 4 figure

Photon Antibunching and Collective Effects in the Fluorescence of Single Bichromophoric Molecules

The fluorescence of individual pairs of perylenemonoimide chromophores coupled via a short rigid linker is investigated. Photon antibunching is reported, indicating collective effects in the fluorescence, which are further substantiated by the observation of collective triplet off times and triplet lifetime shortening. The experimental findings are analyzed in terms of singlet-singlet and singlet-triplet annihilation based on Förster type energy transfer. The results reported here demonstrate that the statistical properties of the emission light of isolated single quantum systems can serve as a hallmark of intermolecular interactions.

Photon Antibunching and Collective Effects in the Fluorescence of Single Bichromophoric Molecules

The fluorescence of individual pairs of perylenemonoimide chromophores coupled via a short rigid linker is investigated. Photon antibunching is reported, indicating collective effects in the fluorescence, which are further substantiated by the observation of collective triplet off times and triplet lifetime shortening. The experimental findings are analyzed in terms of singlet-singlet and singlet-triplet annihilation based on Förster type energy transfer. The results reported here demonstrate that the statistical properties of the emission light of isolated single quantum systems can serve as a hallmark of intermolecular interactions