Coherent population trapping resonances in thermal 85Rb vapor:: D1 versus D2 line excitation

We have compared coherent population trapping (CPT) resonances, both experimentally and theoretically, for excitation of the D-1 and D-2 transitions of thermal Rb-85 vapor. Excitation of the D-1 line results in greater resonance contrast than excitation of the D-2 line and in a reduction in the resonance width, in agreement with theoretical expectations. These results translate into a nearly tenfold improvement in performance for the application of CPT resonances to a frequency standard or a sensitive magnetometer when the D-1 line, rather than the D-2 line, is used. (C) 2002 Optical Society of America.