113 research outputs found
Casimir-Polder effect with thermally excited surfaces
We take a closer look at the fundamental Casimir-Polder interaction between
quantum particles and dispersive dielectric surfaces with surface polariton or
plasmon resonances. Linear response theory shows that in the near field, van
der Waals, regime the free energy shift of a particle contains a thermal
component that depends exclusively on the population/excitation of the
evanescent surface polariton/plasmon modes. Our work makes evident the link
between particle surface interaction and near field thermal emission and
demonstrates how this can be used to engineer Casimir-Polder forces. We also
examine how the exotic effects of surface waves are washed out as the distance
from the surface increases. In the case of molecules or excited state atoms,
far field approximations result in a classical dipole-dipole interaction which
depends on the surface reflectivity and the mean number of photons at the
frequency of the atomic/molecular transition. Finally we present numerical
results for the CP interaction between Cs atoms and various dielectric surfaces
with a single polariton resonance and discuss the implications of temperature
and retardation effects for specific spectroscopic experiments.Comment: accepted in Phys. Rev.
Sub-Doppler resonances in the back-scattered light from random porous media infused with Rb vapor
We report on the observation of sub-Doppler resonances on the back-scattered
light from a random porous glass medium with rubidium vapor filling its
interstices. The sub-Doppler spectral lines are the consequence of saturated
absorption where the incident laser beam saturates the atomic medium and the
back-scattered light probes it. Some specificities of the observed spectra
reflect the transient atomic evolution under confinement inside the pores.
Simplicity, robustness and potential miniaturization are appealing features of
this system as a spectroscopic reference.Comment: 6 pages, 4 figure
Multilayered Waveguides for Increasing the Gain Bandwidth of Integrated Amplifiers
Published versio
Integrated magneto-optical traps on a chip using silicon pyramid structures
International audienceWe have integrated magneto-optical traps (MOTs) into an atom chip by etching pyramids into a silicon wafer. These have been used to trap atoms on the chip, directly from a room temperature vapor of rubidium. This new atom trapping method provides a simple way to integrate several atom sources on the same chip. It represents a substantial advance in atom chip technology and offers new possibilities for atom chip applications such as integrated single atom or photon sources and molecules on a chip
Nonlinear atomic spectroscopy inside a random porous medium
International audienceWe studied a novel spectroscopy setup where alkali atoms are infused in random micro-porous glass and the light probing the atoms have a diffuse nature after the propagation in this strong scattering medium
ICP polishing of silicon for high quality optical resonators on a chip
Miniature concave hollows, made by wet etching silicon through a circular
mask, can be used as mirror substrates for building optical micro-cavities on a
chip. In this paper we investigate how ICP polishing improves both shape and
roughness of the mirror substrates. We characterise the evolution of the
surfaces during the ICP polishing using white-light optical profilometry and
atomic force microscopy. A surface roughness of 1 nm is reached, which reduces
to 0.5 nm after coating with a high reflectivity dielectric. With such smooth
mirrors, the optical cavity finesse is now limited by the shape of the
underlying mirror
Characteristics of integrated magneto-optical traps for atom chips
International audienceWe investigate the operation of pyramidal magneto-optical traps (MOTs) microfabricated in silicon. Measurements of the loading and loss rates give insight into the role of the nearby surface in the MOT dynamics. Studies of the fluorescence versus laser frequency and intensity allow us to develop a simple theory of operation. The number of 85Rb atoms trapped in the pyramid is approximately L6, where L . 6 is the size in mm. This follows quite naturally from the relation between capture velocity and size and differs from the L3.6 often used to describe larger MOTs. Our results constitute substantial progress towards fully integrated atomic physics experiments and devices
Enzymatic and mRNA Transcript Response of Ovine 6-Phosphogluconate Dehydrogenase (6PGD) in Respect to Different Milk Yield
Ovine 6-phosphogluconate dehydrogenase (6PGD) is an enzyme of the pentose phosphate pathway, providing the necessary compounds of NADPH for the synthesis of fatty acids. Much of research has been conducted both on enzymatic level and on molecular level. However, to our knowledge, any correlation between enzymatic activity and 6PGD gene expression pattern related to different physiological stages has not been yet reported. With this report, we tried to highlight if any correlation between enzymatic activity and expression of ovine 6PGD gene exists, in respect to different milk yield. According to the determined enzymatic activities and adipocytes characteristics, ewes with low milk production possessed a greater (P ≤ .001) 6PGD activity and larger adipocytes than the highly productive ewes. Although 6PGD expression pattern was higher in low milk yield ewes than in ewes with high milk production, this difference was not found statistically significant. Thus, 6PGD gene expression pattern was not followed by so rapid and great/sizeable changes as it was observed for its respective enzymatic activity, suggesting that other mechanisms such as post translation regulation may be involved in the regulation of the respective gene
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