Phase contrast imaging of Bose condensed clouds

TL;DR

This paper demonstrates a phase contrast imaging technique for in situ observation of Bose-Einstein condensates at finite temperature, enabling precise measurement of phase shifts and density profiles for comparison with mean-field models.

Contribution

The study introduces an accurate phase contrast imaging method that measures the absolute phase shift and density profiles of BECs, facilitating direct comparison with theoretical models.

Findings

Accurate in situ phase shift measurements of BECs and thermal clouds.

Density profiles fitted with only chemical potential and temperature.

Method allows comparison with mean-field interaction models.

Abstract

Phase contrast imaging is used to observe Bose-Einstein condensates (BECs) at finite temperature in situ. The imaging technique is used to accurately derive the absolute phase shift of a probe laser beam due to both the condensate and the thermal cloud. The accuracy of the method is enhanced by using the periodicity of the intensity signal as a function of the accumulated phase. The measured density profiles can be described using a two relevant parameter fit, in which only the chemical potential and the temperature are to be determined. This allows us to directly compare the measured density profiles to different mean-field models in which the interaction between the condensed and thermal atoms is taken into account to various degrees.