15 research outputs found
Sympathetic Cooling Simulations with a Variable Time Step
In this paper we present a new variable time step criterion for the
velocity-Verlet algorithm allowing to correctly simulate the dynamics of
charged particles exchanging energy via Coulomb collisions while minimising
simulation time. We present physical arguments supporting the use of the
criterion along with numerical results proving its validity. We numerically
show that ions with 18 meV initial energy can be
captured and sympathetically cooled by a Coulomb crystal of
and in less than 10 ms, an important result for the GBAR
project.Comment: LEAP 2016 proceedin
Faraday optical isolator in the 9.2 m range for QCL applications
We have fabricated and characterized a n-doped InSb Faraday isolator in the
mid-IR range (9.2 m). A high isolation ratio of 30 dB with a
transmission over 80% (polarizer losses not included) is obtained at room
temperature. Further possible improvements are discussed. A similar design can
be used to cover a wide wavelength range (lambda ~ 7.5-30 m)
Two-photon spectroscopy of trapped HD ions in the Lamb-Dicke regime
We study the feasibility of nearly-degenerate two-photon rovibrational
spectroscopy in ensembles of trapped, sympathetically cooled hydrogen molecular
ions using a resonance-enhanced multiphoton dissociation (REMPD) scheme. Taking
advantage of quasi-coincidences in the rovibrational spectrum, the excitation
lasers are tuned close to an intermediate level to resonantly enhance
two-photon absorption. Realistic simulations of the REMPD signal are obtained
using a four-level model that takes into account saturation effects, ion
trajectories, laser frequency noise and redistribution of population by
blackbody radiation. We show that the use of counterpropagating laser beams
enables optical excitation in an effective Lamb-Dicke regime. Sub-Doppler lines
having widths in the 100 Hz range can be observed with good signal-to-noise
ratio for an optimal choice of laser detunings. Our results indicate the
feasibility of molecular spectroscopy at the accuracy level for
improved tests of molecular QED, a new determination of the proton-to-electron
mass ratio, and studies of the time (in)dependence of the latter.Comment: 16 pages, 17 figure
Cooling antihydrogen ions for the free-fall experiment GBAR
We discuss an experimental approach allowing to prepare antihydrogen atoms
for the GBAR experiment. We study the feasibility of all necessary experimental
steps: The capture of incoming ions at keV energies in a deep
linear RF trap, sympathetic cooling by laser cooled Be ions, transfer to a
miniaturized trap and Raman sideband cooling of an ion pair to the motional
ground state, and further reducing the momentum of the wavepacket by adiabatic
opening of the trap. For each step, we point out the experimental challenges
and discuss the efficiency and characteristic times, showing that capture and
cooling are possible within a few seconds.Comment: 10 pages, 5 figure
Vibrational spectroscopy of H2+: hyperfine structure of two-photon transitions
We present the computation of two-photon transition spectra between
ro-vibrational states of the H2+ molecular ion, including the effects of
hyperfine structure and excitation polarization. The reduced two-photon matrix
elements are obtained by means of a variational method. We discuss the
implications of our results for high-resolution spectroscopy of H2+
Narrow-line phase-locked quantum cascade laser in the 9.2 micron range
We report on the operation of a 50 mW continuous wave quantum cascade laser
(QCL) in the 9.2 micrometer range, phase locked to a single mode CO2 laser with
a tunable frequency offset. The wide free running emission spectrum of the QCL
(3-5 MHz) is strongly narrowed down to the kHz range making it suitable for
high resolution molecular spectroscopy.Comment: 4 page
OSCILLATEUR PARAMETRIQUE OPTIQUE, EN REGIME CONTINU, DIVISEUR COHERENT DE FREQUENCE PAR TROIS (APPLICATION A LA METROLOGIE DES FREQUENCES OPTIQUES)
ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF
Stimulated Brillouin gain spectroscopy in a confined spatio-temporal domain (30 μm, 170 ns)
The Brillouin gain spectrum of a test sample (liquid acetone at room temperature) on scales simultaneously confined in space (~30 μm) and time (~170 ns) is reported. This is done using a pulsed stimulated Brillouin scattering gain spectrometer in a θ ≈ 90° crossing beam configuration. After having identified and corrected for different sources of background signals, we obtained a Brillouin gain spectrum allowing an accurate measurement (MHz range) of the Brillouin frequency (few GHz). This is of interest for probing acoustic properties of transparent media subjected to repetitive fast transient phenomena on small length scales
Narrow-line phase-locked quantum cascade laser in the 9.2~micron range.
4 pagesWe report on the operation of a 50~mW continuous wave quantum cascade laser (QCL) in the 9.2 micrometer range, phase locked to a single mode CO2 laser with a tunable frequency offset. The wide free running emission spectrum of the QCL (3-5~MHz) is strongly narrowed down to the kHz range making it suitable for high resolution molecular spectroscopy