1,240 research outputs found
An Alkali-Vapor Cell with Metal Coated Windows for Efficient Application of an Electric Field
We describe the implementation of a cylindrical T-shaped alkali-vapor cell
for laser spectroscopy in the presence of a longitudinal electric field. The
two windows are used as two electrodes of the high-voltage assembly, which is
made possible by a metallic coating which entirely covers the inner and outer
sides of the windows except for a central area to let the laser beams in and
out of the cell. This allows very efficient application of the electric field,
up to 2 kV/cm in a rather dense superheated vapor, even when significant
photoemission takes place at the windows during pulsed laser irradiation. The
body of the cell is made of sapphire or alumina ceramic to prevent large
currents resulting from surface conduction observed in cesiated glass cells.
The technique used to attach the monocrystalline sapphire windows to the cell
body causes minimal stress birefringence in the windows. In addition,
reflection losses at the windows can be made very small. The vapor cell
operates with no buffer gas and has no magnetic part. The use of this kind of
cell has resulted in an improvement of the signal-to-noise ratio in the
measurement of Parity Violation in cesium vapor underway at ENS, Paris. The
technique can be applied to other situations where a brazed assembly would give
rise to unacceptably large birefringence in the windows
Measurement of the parity violating 6S-7S transition amplitude in cesium achieved within 2 \times 10^{-13} atomic-unit accuracy by stimulated-emission detection
We exploit the process of asymmetry amplification by stimulated emission
which provides an original method for parity violation (PV) measurements in a
highly forbidden atomic transition. The method involves measurements of a
chiral, transient, optical gain of a cesium vapor on the 7S-6P_{3/2}
transition, probed after it is excited by an intense, linearly polarized,
collinear laser, tuned to resonance for one hyperfine line of the forbidden
6S-7S transition in a longitudinal electric field. We report here a 3.5 fold
increase, of the one-second-measurement sensitivity, and subsequent reduction
by a factor of 3.5 of the statistical accuracy compared with our previous
result [J. Gu\'ena et al., Phys. Rev. Lett. 90, 143001 (2003)]. Decisive
improvements to the set-up include an increased repetition rate, better
extinction of the probe beam at the end of the probe pulse and, for the first
time to our knowledge, the following: a polarization-tilt magnifier,
quasi-suppression of beam reflections at the cell windows, and a Cs cell with
electrically conductive windows. We also present real-time tests of systematic
effects, consistency checks on the data, as well as a 1% accurate measurement
of the electric field seen by the atoms, from atomic signals. PV measurements
performed in seven different vapor cells agree within the statistical error.
Our present result is compatible with the more precise Boulder result within
our present relative statistical accuracy of 2.6%, corresponding to a 2 \times
10^{-13} atomic-unit uncertainty in E_1^{pv}. Theoretical motivations for
further measurements are emphasized and we give a brief overview of a recent
proposal that would allow the uncertainty to be reduced to the 0.1% level by
creating conditions where asymmetry amplification is much greater.Comment: Article 21 pages, 6 figures, 3 tables Typos, addition of few comments
and little more data (1 week) leading to a slight reduction of the error bar
Accepted for publication in Phys.Rev.
A new Manifestation of Atomic Parity Violation in Cesium: a Chiral Optical Gain induced by linearly polarized 6S-7S Excitation
We have detected, by using stimulated emission, an Atomic Parity Violation
(APV) in the form of a chiral optical gain of a cesium vapor on the 7S -
6P transition,consecutive to linearly polarized 6S-7S excitation. We
demonstrate the validity of this detection method of APV, by presenting a 9%
accurate measurement of expected sign and magnitude. We underline several
advantages of this entirely new approach in which the cylindrical symmetry of
the set-up can be fully exploited. Future measurements at the percent level
will provide an important cross-check of an existing more precise result
obtained by a different method.Comment: 4 pages, 2 figure
Selective Reflection Spectroscopy at the Interface between a Calcium Fluoride Window and Cs Vapour
A special vapour cell has been built, that allows the measurement of the
atom-surface van der Waals interaction exerted by a CaF2 window at the
interface with Cs vapour. Mechanical and thermal fragility of fluoride windows
make common designs of vapour cells unpractical, so that we have developed an
all-sapphire sealed cell with an internal CaF2 window. Although impurities were
accidentally introduced when filling-up the prototype cell, leading to a
line-broadening and shift, the selective reflection spectrum on the Cs D1 line
(894 nm) makes apparent the weak van der Waals surface interaction. The
uncertainties introduced by the effects of these impurities in the van der
Waals measurement are nearly eliminated when comparing the selective reflection
signal at the CaF2 interface of interest, and at a sapphire window of the same
cell. The ratio of the interaction respectively exerted by a sapphire interface
and a CaF2 interface is found to be 0.55 0.25, in good agreement with the
theoretical evaluation of ~0.67.Comment: soumis \`a Appl Phys B MS 4734
Nonlinear magneto-optical resonances at D1 excitation of 85Rb and 87Rb in an extremely thin cell
Nonlinear magneto-optical resonances have been measured in an extremely thin
cell (ETC) for the D1 transition of rubidium in an atomic vapor of natural
isotopic composition. All hyperfine transitions of both isotopes have been
studied for a wide range of laser power densities, laser detunings, and ETC
wall separations. Dark resonances in the laser induced fluorescence (LIF) were
observed as expected when the ground state total angular momentum F_g was
greater than or equal to the excited state total angular momentum F_e. Unlike
the case of ordinary cells, the width and contrast of dark resonances formed in
the ETC dramatically depended on the detuning of the laser from the exact
atomic transition. A theoretical model based on the optical Bloch equations was
applied to calculate the shapes of the resonance curves. The model averaged
over the contributions from different atomic velocity groups, considered all
neighboring hyperfine transitions, took into account the splitting and mixing
of magnetic sublevels in an external magnetic field, and included a detailed
treatment of the coherence properties of the laser radiation. Such a
theoretical approach had successfully described nonlinear magneto-optical
resonances in ordinary vapor cells. Although the values of certain model
parameters in the ETC differed significantly from the case of ordinary cells,
the same physical processes were used to model both cases. However, to describe
the resonances in the ETC, key parameters such as the transit relaxation rate
and Doppler width had to be modified in accordance with the ETC's unique
features. Agreement between the measured and calculated resonance curves was
satisfactory for the ETC, though not as good as in the case of ordinary cells.Comment: v2: substantial changes and expanded theoretical model; 13 pages, 10
figures; accepted for publication in Physical Review
- …