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.It is a well established matter that the radiation of an oscillating electric dipole can be manipulated if it is placed in front of a planar interface [1]. Experiments investigating this system date back to Drexhage [2] who looked at the influence of a metallic mirror on the fluorescence lifetime of ensembles of Eu 3+ ions. By preparing a large number of samples, each with a different spacing between the mirror and the emitter layer, two major effects were observed. Firstly, it was shown that the decay rate (Γ) oscillates at large distances due to the retarded interaction of the dipoles with their own reflected fields. Secondly, it was shown that Γ is strongly modified very close to the mirror due to the energy transfer to the metal [1,2]. Since that time, numerous works have investigated the modification of spontaneous emission from ensembles in thin dielectric layers [1]. Various key parameters such as the dipole's orientation, its distance to the interface and its quantum efficiency are, however, averaged in ensemble measurements.Due to challenges such as detection sensitivity, photostability and position control, experiments with single emitters have been scarce. Some researchers have nevertheless shown effects of the local dielectric environment by adding an index matching fluid to eliminate an interface [3,4] or by introducing the subwavelength boundary of a sharp tip [5,6]. In this work we study the fluorescence lifetime and intensity of a single molecule at a well-defined orientation and position, while moving an external silver mirror in its vicinity. We also examine the plasmon spectrum of a well-characterized single gold nanoparticle at various locations in front of a dielectric mirror. These experiments allow us to demonstrate, for the first time, both the far-field modulation and the nearfield modification of the total decay rate (Γ) for individual dipoles. Since the far-field modulations are only due to changes in the radiative decay rate (Γ r ) we can determine the quantum efficiency η = Γ r /Γ of each dipole.A theoretical description of dipole decay in multi-layer structures was first developed by Chance et al. [7] and has been expanded by many authors to cover numerous * Present address:FOM-Institute for Atomic and Molecular Physics (AMOLF), 1098 SJ Amsterdam, The Netherlands † Present address:Niels Bohr Institute, 2100 Copenhagen, Denmark ‡ Electronic address: vahid.sandoghdar@ethz.ch situations. In particular, Sullivan and Hall [8] present an elegant plane wave solution that can easily be adapted to our system. For a s...

We report the observation of more than 7 dB of vacuum squeezing from a below-threshold optical parametric oscillator (OPO). We discuss design criteria and experimental considerations for its optimization and demonstrate that the vacuum squeezing can be electro-optically transferred to a bright beam using a feed-forward loop. This is compared with the bright intensity squeezed beam generated by running the OPO as a de-amplifier.

We discuss experimental studies of the interaction between a nanoscopic object and a photonic crystal membrane resonator of quality factor Q=55000. By controlled actuation of a glass fiber tip in the near field of the photonic crystal, we constructed a complete spatio-spectral map of the resonator mode and its coupling with the fiber tip. On the one hand, our findings demonstrate that scanning probes can profoundly influence the optical characteristics and the near-field images of photonic devices. On the other hand, we show that the introduction of a nanoscopic object provides a low loss method for on-command tuning of a photonic crystal resonator frequency. Our results are in a very good agreement with the predictions of a combined numerical/analytical theory.

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We demonstrate a "standing-wave meter" for measuring dispersion and loss along the length of a planar InP-based photonic-crystal waveguide. Light from a tunable cw laser was coupled into a single line-defect waveguide that terminated inside the crystal structure to form a retroreflector. This structure created a standing wave which was imaged using a scanning near-field optical microscope. By measuring the intensity distribution of the standing wave for a range of optical frequencies, waveguide dispersion and loss were measured with high accuracy. Comparisons of the measurement results with three-dimensional numerical simulations reveal that material dispersion effects as small as 0.8% affect the band structure measurably.