Appropriate Probe Condition for Absorption Imaging of Ultracold⁶Li Atoms

Abstract

One of the readily accessible observables in trapped cold-atom experiments is the column density, which is determined from optical depth (OD) obtained from absorption imaging and the absorption cross-section (σ abs ). Here we report on simple and accurate determination of OD for dense gases of light atoms such as lithium-6. We investigate theoretically and experimentally an appropriate condition for the probe intensity and duration to achieve good signal-to-noise ratio by considering the influences of photon recoils and photon shot noises. As a result, we have succeeded in measuring OD which reached 2.5 with a signal-to-noise ratio of 10 under spatial resolution of 1.7 µm.

Detecting Friedel oscillations in ultracold Fermi gases

“…To ensure that the density distribution is not altered significantly during the imaging process the condition δx(t, I) ≤ l should be fulfilled. The full calculation [38] yields an upper bound t max for the illumination…”

Single-shot reconstruction of the density profile of a dense atomic gas

“…The inhomogeneous field of the magnetic trap introduces a spatial dependency in P(t), that is negligible for Ω/2π > 20 kHz (see Section 5.1). In each picture, we choose the extracted fraction in order to bring a different part of the cloud to a level of OD optimal for our imaging parameters, that are appropriate for dense 23 Na BECs [20].…”

Cavity-assisted preparation and detection of a unitary Fermi gas

“…The measurement of dispersive shift probes atom number while limiting resonant light scattering: as the cooperativitiy of the cavity is larger than one, a majority of the light is scattered into the cavity mode, contributing coherently to the measurement signal, as opposed to scattering into free space which amounts to incoherent losses. In addition, this technique is free of saturation and Doppler effects that hinder absorption imaging for light species [55].…”