We present a simple method to measure the radiative and nonradiative recombination rates of individual fluorescent emitters at room temperature. By placing a single molecule successively close and far from a dielectric interface and simultaneously measuring its photoluminescence decay and its orientation, both the radiative and nonradiative recombination rates can be determined. For CdSe nanocrystals, our results demonstrate that the fluorescence quantum efficiency, determined at the single-molecule level, is 98% in average, far above the value expected from conventional ensemble experiments. The bidimensional nature of the transition dipole is also directly evidenced from a single-particle measurement.

We report a spectroscopic study of single colloidal $\mathrm{CdSe}/\mathrm{ZnS}$ nanocrystals at low temperature. We use photon-correlation Fourier spectroscopy, a technique based on measuring the correlations of the intensities detected at the outputs of a Michelson interferometer. Spectral diffusion over a few $\mu \mathrm{eV}$ is evidenced, on a typical time scale of $200\mu \mathrm{s}$. A time resolution as high as $20\mu \mathrm{s}$ is obtained, and an upper limit of $6.5\mu \mathrm{eV}$ emission linewidth is measured, corresponding to a coherence time of at least 200 ps, similar to the values for epitaxial quantum dots.

Coupling photoluminescent emitters to photonic nanostructures depends critically on the emitter orientation. Researchers show that emission polarization analysis can be used to measure the three-dimensional orientation of single nanoemitters, making it possible to isolate nanoemitters whose orientations are favorable for specific nanostructure cavities.

Single colloidal CdSe/ZnS nanocrystals are deposited at various distances from a gold film in order to improve their performance as single-photon sources. Photon antibunching is demonstrated and the experimental curves are accurately fitted by theoretical equations. Emission lifetime and intensity are measured and found in excellent agreement with theoretical values. The various effects of a neighbouring gold film are discussed : interferences of the excitation beam, interferences of the fluorescence light, opening of plasmon and lossy-surface-wave modes, modification of the radiation pattern leading to a modified objective collection efficiency. At 80 nm from the gold film, when using an objective with 0.75 numerical aperture, about a 2.4-fold increase of the detected intensity is evidenced.

We describe a method to probe the spectral fluctuations of a transition over broad ranges of frequencies and timescales with the high spectral resolution of Fourier spectroscopy, and a temporal resolution as high as the excited state lifetime, even in the limit of very low photocounting rates. The method derives from a simple relation between the fluorescence spectral dynamics of a single radiating dipole and its fluorescence intensity correlations at the outputs of a continuously scanning Michelson interferometer. These findings define an approach to investigate the fast fluorescence spectral dynamics of single molecules and other faint light sources beyond the time-resolution capabilities of standard spectroscopy experiments.