Statistical properties of spontaneous emission near a rough surface

We study the lifetime of the excited state of an atom or molecule near a plane surface with a given random surface roughness. In particular, we discuss the impact of the scattering of surface modes within the rough surface. Our study is completed by considering the lateral correlation length of the decay rate and the variance discussing its relation to the C0 correlation

Photonic mode density effects on single-molecule fluorescence blinking

We investigated the influence of the photonic mode density (PMD) on the triplet dynamics of individual chromophores on a dielectric interface by comparing their response in the presence and absence of a nearby gold film. Lifetimes of the excited singlet state were evaluated in ordet to measure directly the PMD at the molecules position. Triplet state lifetimes were simultaneously determined by statistical analysis of the detection time of the fluorescence photons. The observed singlet decay rates are in agreement with the predicted PMD for molecules with different orientations. The triplet decay rate is modified in a fashion correlated to the singlet decay rate. These results show that PMD engineering can lead to an important suppression of the fluorescence, introducing a novel aspect of the physical mechanism to enhance fluorescence intensity in PMD-enhancing systems such as plasmonic devices

Size-Dependence of the Wavefunction of Self-Assembled Quantum Dots

The radiative and non-radiative decay rates of InAs quantum dots are measured by controlling the local density of optical states near an interface. From time-resolved measurements we extract the oscillator strength and the quantum efficiency and their dependence on emission energy. From our results and a theoretical model we determine the striking dependence of the overlap of the electron and hole wavefunctions on the quantum dot size. We conclude that the optical quality is best for large quantum dots, which is important in order to optimally tailor quantum dot emitters for, e.g., quantum electrodynamics experiments.Comment: 5 pages, 3 figure

Measuring the quantum efficiency of single radiating dipoles using a scanning mirror

Using scanning probe techniques, we show the controlled manipulation of the radiation from single dipoles. In one experiment we study the modification of the fluorescence lifetime of a single molecular dipole in front of a movable silver mirror. A second experiment demonstrates the changing plasmon spectrum of a gold nanoparticle in front of a dielectric mirror. Comparison of our data with theoretical models allows determination of the quantum efficiency of each radiating dipole.Comment: 4 pages, 4 figure

Metallo-dielectric hybrid antennas for ultrastrong enhancement of spontaneous emission

We devise new optical antennas that reduce the excited-state radiative lifetimes of emitters to the order of 100 femtoseconds while maintaining quantum efficiencies of about 80% at a broadband operation. Here, we combine metallic nanoparticles with planar dielectric structures and exploit design strategies from plasmonic nanoantennas and concepts from Cavity Quantum Electrodynamics to maximize the local density of states and minimize the nonradiative losses incurred by the metallic constituents. The proposed metallo-dielectric hybrid antennas promise important impact on various fundamental and applied research fields, including photophysics, ultrafast plasmonics, bright single photon sources and Raman spectroscopy

Observation of modified radiative properties of cold atoms in vacuum near a dielectric surface

We have observed a distance-dependent absorption linewidth of cold $^{87}$Rb atoms close to a dielectric-vacuum interface. This is the first observation of modified radiative properties in vacuum near a dielectric surface. A cloud of cold atoms was created using a magneto-optical trap (MOT) and optical molasses cooling. Evanescent waves (EW) were used to observe the behavior of the atoms near the surface. We observed an increase of the absorption linewidth with up to 25% with respect to the free-space value. Approximately half the broadening can be explained by cavity-quantum electrodynamics (CQED) as an increase of the natural linewidth and inhomogeneous broadening. The remainder we attribute to local Stark shifts near the surface. By varying the characteristic EW length we have observed a distance dependence characteristic for CQED.Comment: 6 pages, 6 figures, some minor revision

Strongly Coupled Matter-Field and Non-Analytic Decay Rate of Dipole Molecules in a Waveguide

The decay rate \gam of an excited dipole molecule inside a waveguide is evaluated for the strongly coupled matter-field case near a cutoff frequency \ome_c without using perturbation analysis. Due to the singularity in the density of photon states at the cutoff frequency, we find that \gam depends non-analytically on the coupling constant $\ggg$ as $\ggg^{4/3}$. In contrast to the ordinary evaluation of \gam which relies on the Fermi golden rule (itself based on perturbation analysis), \gam has an upper bound and does not diverge at \ome_c even if we assume perfect conductance in the waveguide walls. As a result, again in contrast to the statement found in the literature, the speed of emitted light from the molecule does not vanish at \ome_c and is proportional to $c\ggg^{2/3}$ which is on the order of $10^3 \sim 10^4$ m/s for typical dipole molecules.Comment: 4 pages, 2 figure

A multiple-scattering approach to interatomic interactions and superradiance in inhomogeneous dielectrics

The dynamics of a collection of resonant atoms embedded inside an inhomogeneous nondispersive and lossless dielectric is described with a dipole Hamiltonian that is based on a canonical quantization theory. The dielectric is described macroscopically by a position-dependent dielectric function and the atoms as microscopic harmonic oscillators. We identify and discuss the role of several types of Green tensors that describe the spatio-temporal propagation of field operators. After integrating out the atomic degrees of freedom, a multiple-scattering formalism emerges in which an exact Lippmann-Schwinger equation for the electric field operator plays a central role. The equation describes atoms as point sources and point scatterers for light. First, single-atom properties are calculated such as position-dependent spontaneous-emission rates as well as differential cross sections for elastic scattering and for resonance fluorescence. Secondly, multi-atom processes are studied. It is shown that the medium modifies both the resonant and the static parts of the dipole-dipole interactions. These interatomic interactions may cause the atoms to scatter and emit light cooperatively. Unlike in free space, differences in position-dependent emission rates and radiative line shifts influence cooperative decay in the dielectric. As a generic example, it is shown that near a partially reflecting plane there is a sharp transition from two-atom superradiance to single-atom emission as the atomic positions are varied.Comment: 18 pages, 4 figures, to appear in Physical Review