Low noise measurement method based on differential optical interferometer for cold atom experiments

We proposed and realized a low noise measurement method based on differential optical interferometer to measure trapped cold atoms in a magneto-optical trap (MOT). The configuration is based on a Mach-Zehnder type interferometer, which is composed of two beams of different frequencies. A long-term stability in phase monitor has been obtained by use of the vibration immune mechanism through subtraction of the interferograms imaged on the two photodetectors. With this new configuration, the noise caused by environmental perturbation is greatly reduced at low frequency while the signal of phase shift keeps a good long-term stability.