Nondestructive interferometric characterization of an optical dipole trap

A method for nondestructive characterization of a dipole-trapped atomic sample is presented. It relies on a measurement of the phase shift imposed by cold atoms on an optical pulse that propagates through a free-space Mach-Zehnder interferometer. Using this technique we are able to determine, with very good accuracy, relevant trap parameters such as the atomic sample temperature, trap oscillation frequencies, and loss rates. Another important feature is that our method is faster than conventional absorption or fluorescence techniques, allowing the combination of high-dynamical range measurements and a reduced number of spontaneous emission events per atom