204 research outputs found
Nonclassical radiation from diamond nanocrystals
The quantum properties of the fluorescence light emitted by diamond
nanocrystals containing a single nitrogen-vacancy (NV) colored center is
investigated. We have observed photon antibunching with very low background
light. This system is therefore a very good candidate for the production of
single photon on demand. In addition, we have measured larger NV center
lifetime in nanocrystals than in the bulk, in good agreement with a simple
quantum electrodynamical model.Comment: 8 pages, 5 figures, revised version, to appear in PR
Quantum plasmonics: second-order coherence of surface plasmons launched by quantum emitters into a metallic film
We address the issue of the second-order coherence of single surface plasmons
launched by a quantum source of light into extended gold films. The quantum
source of light is made of a scanning fluorescent nanodiamond hosting five
nitrogen-vacancy (NV) color centers. By using a specially designed microscopy
that combines near-field optics with far-field leakage-radiation microscopy in
the Fourier space and adapted spatial filtering, we find that the quantum
statistics of the initial source of light is preserved after conversion to
surface plasmons and propagation along the polycrystalline gold film.Comment: Second version with minor changes made to comply with Referees'
comments. Editorially approved for publication in Phys. Rev. B on 22 June
201
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
Photophysics of single nitrogen-vacancy centers in diamond nanocrystals
International audienceA study of the photophysical properties of nitrogen-vacancy (NV) color centers in diamond nanocrystals of size 50 nm or below is carried out by means of second-order time-intensity photon correlation and cross-correlation measurements as a function of the excitation power for both pure charge states, neutral and negatively charged, as well as for the photochromic state, where the center switches between both states at any power. A dedicated three-level model implying a shelving level is developed to extract the relevant photophysical parameters coupling all three levels. Our analysis confirms the very existence of the shelving level for the neutral NV center. It is found that it plays a negligible role on the photophysics of this center, whereas it is responsible for an increasing photon bunching behavior of the negative NV center with increasing power. From the photophysical parameters, we infer a quantum efficiency for both centers, showing that it remains close to unity for the neutral center over the entire power range, whereas it drops with increasing power from near unity to approximately 0.5 for the negative center. The photophysics of the photochromic center reveals a rich phenomenology that is to a large extent dominated by that of the negative state, in agreement with the excess charge release of the negative center being much slower than the photon emission process
Optical in situ size determination of single lanthanide-ion doped oxide nanoparticles
International audienceWe show that the size of a lanthanide-ion doped nanoparticle can be accurately determined from its luminosity. The optically determined size distribution is in very good agreement with the distribution obtained from transmission electron microscopy. These data confirm that single nanoparticles are visualized in microscopy experiments. Nanoparticles as small as 13 nm are detectable with integration times of 500 ms. (c) 2006 American Institute of Physics
Percolation transition in the porous structure of latex-templated silica monoliths
International audiencePorous sol-gel silica monoliths are prepared using PMMA nanoparticles, 60 nm in diameter, as sacrificial templates. The pore-structure of the calcined pellets is investigated through nitrogen adsorption to assess the evolution of the porosity when varying the amount of porogen. The latex templated monoliths present a well defined spherical extrinsic porosity and an intrinsic microporosity due to preparation process. As a result of a careful analysis of the adsorption hysteresis, we identify a percolation threshold of the spherical porosity around 30% volume fraction. This phenomenon, similar to the percolation previously observed in latex-templated silica films, opens the way to the use of latex-templated porous silica monoliths with a tailorable and reliable pore structure
Single photon quantum cryptography
We report the full implementation of a quantum cryptography protocol using a
stream of single photon pulses generated by a stable and efficient source
operating at room temperature. The single photon pulses are emitted on demand
by a single nitrogen-vacancy (NV) color center in a diamond nanocrystal. The
quantum bit error rate is less that 4.6% and the secure bit rate is 9500
bits/s. The overall performances of our system reaches a domain where single
photons have a measurable advantage over an equivalent system based on
attenuated light pulses.Comment: 4 pages, 3 figure
Sensor-integrated fluorescent microarray for ultrahigh sensitivity direct-imaging bioassays: Role of a high rejection of excitation light
International audienceFluorescent microarrays exploit fluorescent labeled targets bound to immobilized biomolecular probes. Their signal-to-noise ratio is limited by the collection aperture in common confocal geometries. Taking advantage of a very high rejection filter deposited onto a silicon arrayed detector (coupled-charge device or complementary metal-oxide semiconductor), it is demonstrated that a highly compact lens-free assay with photon collection of order unity operates with a 30-fold improvement over a conventional (substrate + free-space optics) scheme. Through analysis of improvements over the present demonstrator, a single molecule per pixel sensitivity is predicted
Enhancing Magnetic Light Emission with All-Dielectric Optical Nanoantennas
Electric and magnetic optical fields carry the same amount of energy. Nevertheless, the efficiency with which matter interacts with electric optical fields is commonly accepted to be at least 4 orders of magnitude higher than with magnetic optical fields. Here, we experimentally demonstrate that properly designed photonic nanoantennas can selectively manipulate the magnetic versus electric emission of luminescent nanocrystals. In particular, we show selective enhancement of magnetic emission from trivalent europium-doped nanoparticles in the vicinity of a nanoantenna tailored to exhibit a magnetic resonance. Specifically, by controlling the spatial coupling between emitters and an individual nanoresonator located at the edge of a near field optical scanning tip, we record with nanoscale precision local distributions of both magnetic and electric radiative local densities of states (LDOS). The map of the radiative LDOS reveals the modification of both the magnetic and electric quantum environments induced by the presence of the nanoantenna. This manipulation and enhancement of magnetic light-matter interaction by means of nanoantennas opens up new possibilities for the research fields of opto-electronics, chiral optics, nonlinear&nano-optics, spintronics and metamaterials, amongst others.Peer ReviewedPostprint (author's final draft
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