Direct Calibration of Laser Intensity via Ramsey Interferometry for Cold Atom Imaging

Abstract

A majority of ultracold atom experiments utilize resonant absorption imaging techniques to obtain the atomic density. To make well-controlled quantitative measurements, the optical intensity of the probe beam must be precisely calibrated in units of the atomic saturation intensity $I_{\mathrm{sat}}$. In quantum gas experiments, the atomic sample is enclosed in an ultra-high vacuum system that introduces loss and limits optical access; this precludes a direct determination of the intensity. Here, we use quantum coherence to create a robust technique for measuring the probe beam intensity in units of $I_{\mathrm{sat}}$ via Ramsey interferometry. Our technique characterizes the ac Stark shift of the atomic levels due to an off-resonant probe beam. Furthermore, this technique gives access to the spatial variation of the probe intensity at the location of the atomic cloud. By directly measuring the probe intensity just before the imaging sensor our method in addition yields a direct calibration of imaging system losses as well as the quantum efficiency of the sensor.

arXiv comment15 pages, 7 figures

References in corpus (6)

• Strong saturation absorption imaging of dense clouds of ultracold atoms
• Momentum distribution and correlation function of quasicondensates in elongated traps
• Calibrating High Intensity Absorption Imaging of Ultracold Atoms
• Inhomogeneous Light Shift Effects on Atomic Quantum State Evolution in Non-Destructive Measurements
• Ramsey imaging of optical traps
• Quantum Back-action Limits in Dispersively Measured Bose-Einstein Condensates

Cited by in corpus (2)

• Quantum Back-action Limits in Dispersively Measured Bose-Einstein Condensates
• Weak-Measurement-Induced Heating in Bose-Einstein Condensates