270 research outputs found
Extinction imaging of a single quantum emitter in its bright and dark states
Room temperature detection of single quantum emitters has had a broad impact
in fields ranging from biophysics to material science, photophysics, or even
quantum optics. These experiments have exclusively relied on the efficient
detection of fluorescence. An attractive alternative would be to employ direct
absorption, or more correctly expressed "extinction" measurements. Indeed,
small nanoparticles have been successfully detected using this scheme in
reflection and transmission. Coherent extinction detection of single emitters
has also been reported at cryogenic temperatures, but their room temperature
implementation has remained a great laboratory challenge owing to the expected
weak signal-to-noise ratio. Here we report the first extinction study of a
single quantum emitter at ambient condition. We obtain a direct measure for the
extinction cross section of a single semiconductor nanocrystal both during and
in the absence of fluorescence, for example in the photobleached state or
during blinking off-times. Our measurements pave the way for the detection and
absorption spectroscopy of single molecules or clusters of atoms even in the
quenched state
Modification of single molecule fluorescence by a scanning probe
We examine the optical near-field interaction between different types of scanning tips and single oriented fluorescent molecules. We demonstrate the influence of a tip on the excitation intensity as well as on the integrated fluorescence signal, the excited state lifetime, and the angular emission of single molecules. By using a standard model describing the radiation of an oscillating dipole close to a nanosphere or a flat interface, we interpret our observations and describe some central criteria for obtaining fluorescence enhancement or quenchin
Spontaneous emission of a nanoscopic emitter in a strongly scattering disordered medium
Fluorescence lifetimes of nitrogen-vacancy color centers in individual
diamond nanocrystals were measured at the interface between a glass substrate
and a strongly scattering medium. Comparison of the results with values
recorded from the same nanocrystals at the glass-air interface revealed
fluctuations of fluorescence lifetimes in the scattering medium. After
discussing a range of possible systematic effects, we attribute the observed
lengthening of the lifetimes to the reduction of the local density of states.
Our approach is very promising for exploring the strong three-dimensional
localization of light directly on the microscopic scale.Comment: 9 pages, 4 figure
Realization of two Fourier-limited solid-state single-photon sources
We demonstrate two solid-state sources of indistinguishable single photons.
High resolution laser spectroscopy and optical microscopy were combined at T =
1.4 K to identify individual molecules in two independent microscopes. The
Stark effect was exploited to shift the transition frequency of a given
molecule and thus obtain single photon sources with perfect spectral overlap.
Our experimental arrangement sets the ground for the realization of various
quantum interference and information processing experiments.Comment: 6 page
Molecules as Sources for Indistinguishable Single Photons
We report on the triggered generation of indistinguishable photons by
solid-state single-photon sources in two separate cryogenic laser scanning
microscopes. Organic fluorescent molecules were used as emitters and
investigated by means of high resolution laser spectroscopy. Continuous-wave
photon correlation measurements on individual molecules proved the isolation of
single quantum systems. By using frequency selective pulsed excitation of the
molecule and efficient spectral filtering of its emission, we produced
triggered Fourier-limited single photons. In a further step, local electric
fields were applied to match the emission wavelengths of two different
molecules via Stark effect. Identical single photons are indispensible for the
realization of various quantum information processing schemes proposed. The
solid-state approach presented here prepares the way towards the integration of
multiple bright sources of single photons on a single chip.Comment: Accepted for publication in J. Mod. Opt. This is the original
submitted versio
High-cooperativity nanofiber laser
Cavity-free efficient coupling between emitters and guided modes is of great current interest for nonlinear quantum optics as well as efficient and scalable quantum information processing. In this work, we extend these activities to the coupling of organic dye molecules to a highly confined mode of a nanofiber, allowing mirrorless and low-threshold laser action in an effective mode volume of less than 100 femtoliters. We model this laser system based on semi-classical rate equations and present an analytic compact form of the laser output intensity. Despite the lack of a cavity structure, we achieve a coupling efficiency of the spontaneous emission to the waveguide mode of 0.07(0.01), in agreement with our calculations. In a further experiment, we also demonstrate the use of a plasmonic nanoparticle as a dispersive output coupler. Our laser architecture is promising for a number of applications in optofluidics and provides a fundamental model system for studying nonresonant feedback stimulated emission
Controlled photon transfer between two individual nanoemitters via shared high-Q modes of a microsphere resonator
We realize controlled cavity-mediated photon transfer between two single
nanoparticles over a distance of several tens of micrometers. First, we show
how a single nanoscopic emitter attached to a near-field probe can be coupled
to high-Q whispering-gallery modes of a silica microsphere at will. Then we
demonstrate transfer of energy between this and a second nanoparticle deposited
on the sphere surface. We estimate the photon transfer efficiency to be about
six orders of magnitude higher than that via free space propagation at
comparable separations.Comment: accepted for publication in Nano Letter
Single-Photon Imaging and Efficient Coupling to Single Plasmons
We demonstrate strong coupling of single photons emitted by individual
molecules at cryogenic and ambient conditions to individual nanoparticles. We
provide images obtained both in transmission and reflection, where an
efficiency greater than 55% was achieved in converting incident narrow-band
photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work
paves the way to spectroscopy and microscopy of nano-objects with sub-shot
noise beams of light and to triggered generation of single plasmons and
electrons in a well-controlled manner
Near-field imaging and frequency tuning of a high-Q photonic crystal membrane microcavity
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 a 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.Comment: 9 pages, 4 figure
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