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Quantum interference; ultracold atoms; thermal averaging.

We have investigated coherent population trapping (CPT) in laser-cooled as well as room-temperature (with and without buffer gas) rubidium atoms. The characteristic broad signal profile emerging from the two-photon Raman resonance for room-temperature atomic vapour is consistent with the theoretical calculation incorporating associated thermal averaging. The spectral width of the dark resonance obtained with cold atoms is found to be broadened, compared to roomtemperature vapour cell, due to the feeble role played by thermal averaging, although the cold atomic sample significantly overcomes the limitation of the transit time broadening. An alternative way to improve transit time is to use a buffer gas, with which we demonstrate that the coherent population trapping signal width is reduced to < 540 Hz.

S Pradhan¹ S Mishra¹ R Behera¹ N Kawade¹ A K Das¹

1. Laser Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400 085, India

Published

February 2014

Early published

15 February 2014