90 research outputs found
Direct Measurement of the Photon Statistics of a Triggered Single Photon Source
We studied intensity fluctuations of a single photon source relying on the
pulsed excitation of the fluorescence of a single molecule at room temperature.
We directly measured the Mandel parameter Q(T) over 4 orders of magnitude of
observation timescale T, by recording every photocount. On timescale of a few
excitation periods, subpoissonian statistics is clearly observed and the
probablility of two-photons events is 10 times smaller than Poissonian pulses.
On longer times, blinking in the fluorescence, due to the molecular triplet
state, produces an excess of noise.Comment: 4 pages, 3 figures, 1 table submitted to Physical Review Letter
Grafting fluorescent nanodiamonds onto optical tips
We recently (Optics Express 17, 19969 (2009)) introduced an all-optical
method for grafting onto the apex of an optical tip a single 20 nm nanodiamond
with single color-center occupancy and used the resulting single-photon tip in
scanning near-field imaging at room temperature, thereby achieving a genuine
scanning single-photon microscopy working in ambient conditions. A variant of
this method is described that allows for attaching several nanodiamonds onto
the tip apex, releasing them all at once and finally recapturing them one by
one by the scanning tip. This underlines the flexibility and powerfulness of
our method and its variant that could be used in applications where a fixed
number of selected optically active nano-objects requires positioning, or
repositioning, at well defined locations with nanometer accuracy.Comment: Minor stylistic changes since first submissio
Enhancing single-molecule photostability by optical feedback from quantum-jump detection
We report an optical technique that yields an enhancement of single-molecule
photostability, by greatly suppressing photobleaching pathways which involve
photoexcitation from the triplet state. This is accomplished by dynamically
switching off the excitation laser when a quantum-jump of the molecule to the
triplet state is optically detected. This procedure leads to a lengthened
single-molecule observation time and an increased total number of detected
photons. The resulting improvement in photostability unambiguously confirms the
importance of photoexcitation from the triplet state in photobleaching
dynamics, and may allow the investigation of new phenomena at the
single-molecule level
Photoluminescence of single colour defects in 50 nm diamond nanocrystals
We used optical confocal microscopy to study optical properties of diamond 50
nm nanocrystals first irradiated with an electron beam, then dispersed as a
colloidal solution and finally deposited on a silica slide. At room
temperature, under CW laser excitation at a wavelength of 514.5 nm we observed
perfectly photostable single Nitrogen-Vacancy (NV) colour defects embedded in
the nanocrystals. From the zero-phonon line around 575 nm in the spectrum of
emitted light, we infer a neutral NV0 type of defect. Such nanoparticle with
intrinsic fluorescence are highly promising for applications in biology where
long-term emitting fluorescent bio-compatible nanoprobes are still missing.Comment: proceedings of ICDS 23 conference (23rd International Conference on
Defects in Semiconductors, July 24 - July 29, 2005, Awaji Island, Hyogo,
Japan); to appear in "Physica B
Study of the optimal conditions for NV- center formation in type 1b diamond, using photoluminescence and positron annihilation spectroscopies
We studied the parameters to optimize the production of negatively-charged
nitrogen-vacancy color centers (NV-) in type~1b single crystal diamond using
proton irradiation followed by thermal annealing under vacuum. Several samples
were treated under different irradiation and annealing conditions and
characterized by slow positron beam Doppler-broadening and photoluminescence
(PL) spectroscopies. At high proton fluences another complex vacancy defect
appears limiting the formation of NV-. Concentrations as high as 2.3 x 10^18
cm^-3 of NV- have been estimated from PL measurements. Furthermore, we inferred
the trapping coefficient of positrons by NV-. This study brings insight into
the production of a high concentration of NV- in diamond, which is of utmost
importance in ultra-sensitive magnetometry and quantum hybrid systems
applications
- …