82 research outputs found
Controlling single diamond NV color center photoluminescence spectrum with a Fabry-Perot microcavity
We present both theoretical and experimental results on fluorescence of
single defect centers in diamond nanocrystals embedded in a planar dielectric
microcavity. From a theoretical point of view, we show that the overall
fluorescence collection efficiency using moderate numerical aperture microscope
objective can be enhanced by using a low quality factor microcavity. This could
be used in particular for low temperature applications where the numerical
aperture of collection microscope objectives is limited due to the experimental
constraints. We experimentally investigate the control of the fluorescence
spectrum of the emitted light from a single center. We show the simultaneous
narrowing of the room temperature broadband emission spectrum and the increase
of the fluorescence spectral density.Comment: 22 pages, 10 figure
Narrow-band single-photon emission in the near infrared for quantum key distribution
We report on the observation of single colour centers in natural diamond
samples emitting in the near infrared region when optically excited.
Photoluminescence of these single emitters have several striking features, such
as a narrow-band fully polarized emission (FWHM 2 nm) around 780 nm, a short
excited-state lifetime of about 2 ns, and perfect photostability at room
temperature under our excitation conditions. We present a detailed study of
their photophysical properties. Development of a triggered single-photon source
relying on this single colour centre is discussed in the prospect of its
application to quantum key distribution.Comment: 9 page
Wheeler's delayed-choice thought experiment: Experimental realization and theoretical analysis
Wheeler has strikingly illustrated the wave-particle duality by the
delayed-choice thought experiment, in which the configuration of a 2-path
interferometer is chosen after a single-photon light-pulsed has entered it. We
present a quantitative theoretical analysis of an experimental realization of
Wheeler's proposal
Experimental realization of Wheeler's delayed-choice GedankenExperiment
The quantum "mystery which cannot go away" (in Feynman's words) of
wave-particle duality is illustrated in a striking way by Wheeler's
delayed-choice GedankenExperiment. In this experiment, the configuration of a
two-path interferometer is chosen after a single-photon pulse has entered it :
either the interferometer is \textit{closed} (\textit{i.e.} the two paths are
recombined) and the interference is observed, or the interferometer remains
\textit{open} and the path followed by the photon is measured. We report an
almost ideal realization of that GedankenExperiment, where the light pulses are
true single photons, allowing unambiguous which-way measurements, and the
interferometer, which has two spatially separated paths, produces high
visibility interference. The choice between measuring either the 'open' or
'closed' configuration is made by a quantum random number generator, and is
space-like separated -- in the relativistic sense -- from the entering of the
photon into the interferometer. Measurements in the closed configuration show
interference with a visibility of 94%, while measurements in the open
configuration allow us to determine the followed path with an error probability
lower than 1%
Balanced homodyne detection in second-harmonic generation microscopy
We demonstrate the association of two-photon nonlinear microscopy with
balanced homodyne detection for investigating second harmonic radiation
properties at nanoscale dimensions. Variation of the relative phase between
second-harmonic and fundamental beams is retrieved, as a function of the
absolute orientation of the nonlinear emitters. Sensitivity down to
approximately 3.2 photon/s in the spatio-temporal mode of the local oscillator
is obtained. This value is high enough to efficiently detect the coherent
second-harmonic emission from a single KTiOPO4 crystal of sub-wavelength size.Comment: 9 pages to appear in Applied Physics Letter
Comparison of the photoluminescence properties of semiconductor quantum dots and non-blinking diamond nanoparticles. Observation of the diffusion of diamond nanoparticles in living cells
Long-term observations of photoluminescence at the single-molecule level were
until recently very diffcult, due to the photobleaching of organic ?uorophore
molecules. Although inorganic semiconductor nanocrystals can overcome this
diffculty showing very low photobleaching yield, they suffer from
photoblinking. A new marker has been recently introduced, relying on diamond
nanoparticles containing photoluminescent color centers. In this work we
compare the photoluminescence of single quantum dots (QDs) to the one of
nanodiamonds containing a single-color center. Contrary to other markers,
photoluminescent nanodiamonds present a perfect photostability and no
photoblinking. At saturation of their excitation, nanodiamonds
photoluminescence intensity is only three times smaller than the one of QDs.
Moreover, the bright and stable photoluminescence of nanodiamonds allows wide
field observations of single nanoparticles motion. We demonstrate the
possibility of recording the tra jectory of such single particle in culture
cells
Magnetometry with nitrogen-vacancy ensembles in diamond based on infrared absorption in a doubly resonant optical cavity
We propose to use an optical cavity to enhance the sensitivity of
magnetometers relying on the detection of the spin state of high-density
nitrogen-vacancy ensembles in diamond using infrared optical absorption. The
role of the cavity is to obtain a contrast in the absorption-detected magnetic
resonance approaching unity at room temperature. We project an increase in the
photon shot-noise limited sensitivity of two orders of magnitude in comparison
with a single-pass approach. Optical losses can limit the enhancement to one
order of magnitude which could still enable room temperature operation.
Finally, the optical cavity also allows to use smaller pumping power when it is
designed to be resonant at both the pump and the signal wavelength
Two-photon real-time device for single-particle holographic tracking (red shot)
Three-dimension real-time tracking of single emitters is an emerging tool for
assessment of biological behavior as intraneuronal transport, for which
spatiotemporal resolution is crucial to understand the microscopic interactions
between molecular motors. We report the use of second harmonic signal from
nonlinear nanoparticles to localize them in a super-localization regime, down
to 15 nm precision, and at high refreshing rates, up to 1.1 kHz, allowing us to
track the particles in real-time. Holograms dynamically displayed on a digital
micro-mirror device are used to steer the excitation laser focus in 3D around
the particle on a specific pattern. The particle position is inferred from the
collected intensities using a maximum likelihood approach. The holograms are
also used to compensate for optical aberrations of the optical system. We
report tracking of particles moving faster than 30 m/s with an uncertainty
on the localization around 40 nm. We have been able to track freely moving
particles over tens of micrometers, and directional intracellular transport in
neurites
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