arXiv subjects

Hector Letellier

Publications and source records attributed to Hector Letellier.

5 recordsLinked to original sources

arXiv2026

In Situ Coherence Measurements of Scattered Light in Magnetically Trapped Cold Atomic Clouds: Probe-Driven Atomic Dynamics

The use of temporal correlations in scattered photons to probe the microscopic dynamics of ultracold quantum gases has emerged as a powerful, minimally destructive approach for in situ analysis. Here, we demonstrate that temporal coherence spectroscopy can quantitatively characterize atomic motion in a magnetic trap, despite the perturbative effects of the probing light. By measuring the first-order correlation function g (1) ($\tau$ ) of light scattered by a 87 Rb cloud confined in a quadrupole trap, we identify radiation-pressure-induced acceleration and heating as the origin of the apparent discrepancy between coherence spectra and temperatures inferred from time-of-flight measurements. A simple dynamical model incorporating these effects restores agreement between theory and experiment, establishing coherence spectroscopy as a reliable in situ probe of velocity distributions in trapped atomic ensembles. Our results pave the way for time-resolved studies of nonequilibrium dynamics and thermalization processes in confined cold gases, complementing conventional destructive imaging techniques.

physics.atom-ph↗

arXiv2024

In-situ measurements of light diffusion in an optically dense atomic ensemble

This study introduces a novel method to investigate in-situ light transport within optically thick ensembles of cold atoms, exploiting the internal structure of alkaline-earth metals. A method for creating an optical excitation at the center of a large atomic cloud is demonstrated, and we observe its propagation through multiple scattering events. In conditions where the cloud size is significantly larger than the transport mean free path, a diffusive regime is identified. We measure key parameters including the diffusion coefficient, transport velocity, and transport time, finding a good agreement with diffusion models. We also demonstrate that the frequency of the photons launched inside the system can be controlled. This approach enables direct time- and space-resolved observation of light diffusion in atomic ensembles, offering a promising avenue for exploring new diffusion regimes.

physics.atom-ph↗

arXiv2024

Magic-wavelength nanofiber-based two-color dipole trap with sub-$\lambda/2$ spacing

We report on the realization and characterization of a novel magic-wavelength nanofiber-based two-color optical dipole trap for cesium that allows us to generate two diametral periodic one-dimensional arrays of trapping sites with a spacing significantly smaller than half the resonant free-space wavelength of the cesium D2 transition. This is achieved by launching a blue-detuned partial standing wave and two red-detuned light fields through the nanofiber. We trap and optically interface the atoms in the resulting periodic optical potential and characterize the trap by measuring the lifetime of the trapped atoms, the atom-light coupling strength, the filling factor, and the trap frequencies in the radial and axial directions. The implementation of this nanofiber-based optical interface with magic trapping wavelengths and sub-$\lambda/2$ spacing is an important step towards the exploration of novel collective radiative effects, such as selective radiance.

physics.atom-ph↗

arXiv2023

Laser frequency stabilization by modulation transfer spectroscopy and balanced detection of molecular iodine for laser cooling of ${}^{174}$Yb

We report laser frequency stabilization by the combination of modulation transfer spectroscopy and balanced detection of a relatively weak hyperfine transition of the R(158)25-0 line of molecular iodine (${}^{127}$I$_{2}$), which is used as a new frequency reference for laser trapping and cooling of ${}^{174}$Yb on the $^{1}S_{0} - {}^{3}P_{1}$ transition. The atomic cloud is characterized by time-of-flight measurements, and an on-resonance optical depth of up to 47 is obtained. We show laser noise reduction and characterize the short-term laser frequency instability by the Allan deviation of the laser fractional frequency. The minimum measured value is 3.9 x $10^{-13}$ at 0.17 s of averaging time.

physics.atom-ph↗

arXiv2023

Loading of a large Yb MOT on the $^1$S$_0$-$^1$P$_1$ transition

We present an experimental setup to laser cool and trap a large number of Ytterbium atoms. Our design uses an oven with an array of microtubes for efficient collimation of the atomic beam and we implement a magneto-optical trap of $^{174}$Yb on the $^1$S$_0$-$^1$P$_1$ transition at 399nm. Despite the absence of a Zeeman slower, we are able to trap up to $N = 10^9$ atoms. We precisely characterize our atomic beam, the loading rate of the magneto-optical trap and several loss mechanisms relevant for trapping a large number of atoms.

physics.atom-ph↗