41 research outputs found
Large 2D Coulomb crystals in a radio frequency surface ion trap
We designed and operated a surface ion trap, with an ion-substrate distance
of 500\mum, realized with standard printed-circuit-board techniques. The trap
has been loaded with up to a few thousand Sr+ ions in the Coulomb-crystal
regime. An analytical model of the pseudo-potential allowed us to determine the
parameters that drive the trap into anisotropic regimes in which we obtain
large (N>150) purely 2D ion Coulomb crystals. These crystals may open a simple
and reliable way to experiments on quantum simulations of large 2D systems.Comment: 4 pages, 4 figure
Double-lambda microscopic model for entangled light generation by four-wave-mixing
Motivated by recent experiments, we study four-wave-mixing in an atomic
double-{\Lambda} system driven by a far-detuned pump. Using the
Heisenberg-Langevin formalism, and based on the microscopic properties of the
medium, we calculate the classical and quantum properties of seed and conju-
gate beams beyond the linear amplifier approximation. A continuous variable
approach gives us access to relative-intensity noise spectra that can be
directly compared to experiments. Restricting ourselves to the cold-atom
regime, we predict the generation of quantum-correlated beams with a
relative-intensity noise spectrum well below the standard quantum limit (down
to -6 dB). Moreover entanglement between seed and conjugate beams measured by
an inseparability down to 0.25 is expected. This work opens the way to the
generation of entangled beams by four-wave mixing in a cold atomic sample.Comment: 11 pages, 6 figures, submitted to PR
Photoionisation loading of large Sr+ ion clouds with ultrafast pulses
This paper reports on photoionisation loading based on ultrafast pulses of
singly-ionised strontium ions in a linear Paul trap. We take advantage of an
autoionising resonance of Sr neutral atoms to form Sr+ by two-photon absorption
of femtosecond pulses at a wavelength of 431nm. We compare this technique to
electron-bombardment ionisation and observe several advantages of
photoionisation. It actually allows the loading of a pure Sr+ ion cloud in a
low radio-frequency voltage amplitude regime. In these conditions up to 4x10^4
laser-cooled Sr+ ions were trapped
Optimization of the Anisotropic Gaussian Kernel for Text Segmentation and Parameter Extraction
Naphthalocyanine-based time reversal mirror at 800 nm
International audienceWe performed pulse shaping and time reversal experiments using spectral holography based on persistent spectral hole burning in free-base naphthalocyanine-doped films. The application of a new pulse re-compression scheme based on a programmable hole burning material acting as a time reversal mirror is considered. In this work, we adapted the Fourier transform spectral interferometry technique for measuring the amplitude and phase of photon echo signals produced by diffraction of femtosecond pulses on a spectral hologram. We therefore demonstrated that we could control the pulses diffracted from the hologram by shaping and then characterizing these pulses in both amplitude and phase by spectral interferometry. © 2003 Elsevier B.V. All rights reserved
Electron- and hole-spin relaxation within excitons in GaAs quantum wells by non-degenerate pump-and-probe measurements
Conversion of high-power 15-fs visible pulses to the mid infrared
We measure the efficiency of converting high-power 15-fs 0.8-\u3bcm pulses to the mid infrared in GaAs and GaSe as well as the pulse duration and the spectrum of the infrared radiation that is produced. Free-carrier production limits the conversion efficiency in GaAs to approximately 5
710-7 , allowing us to produce 2.5-pJ, 30-fs pulses spanning the spectral range from 6 to 14 \u3bcm . In GaSe we obtain, in a moderately saturated regime, a conversion efficiency of 7.5
710-5 , limited by two-photon absorption, allowing us to produce pulses of 100-fs duration containing 10 nJ of energy.Peer reviewed: YesNRC publication: Ye
Method for single-shot measurement of the carrier envelope phase of a few-cycle laser pulse
The interference between different harmonics of a few-cycle optical pulse in the region of the spectral overlap is sensitive to the phase of the optical carrier inside the pulse envelope. Near-surface third-harmonic generation from Si(001) combined with second-harmonic generation in a 10-\ub5m-thick \u3b2-barium borate crystal produces sufficiently strong harmonic emission for single-shot measurement. We propose using this technique to measure the carrier envelope phase of high-energy 5-fs pulses.Peer reviewed: YesNRC publication: Ye