Development of optical frequency standards based upon the /sup 2/S/sub 1/2/-/sup 2/D/sub 5/2/ transition in /sup 88/Sr/sup +/ and /sup 87/Sr/sup +/

Abstract

Recent work is presented on the development of an optical frequency standard, based on the /sup 2/S/sub 1/2/-/sup 2/D/sub 5/2/ "clock" transition at 674 nm in two isotopes of strontium. A/spl ap/200 Hz linewidth 674 nm laser has been frequency-stabilised to the centre of the /sup 2/S/sub 1/2/-/sup 2/D/sub 5/2/ transition in two /sup 88/Sr/sup +/ ions, separately confined in two RF traps. The frequency locking algorithm for control of the laser frequency to the transition using the two ions is described. The mean difference of the frequency observed in the two ions is 34(33) Hz, where the number in parenthesis is the standard uncertainty. The Allan deviation of the difference frequency stability was observed to range from 10 Hz to 50 Hz at 30 s. In /sup 87/Sr/sup +/, there are "clock" transitions independent of the first order Zeeman shift; laser cooled /sup 87/Sr/sup +/ ions have been observed in a new trap with an oven containing isotopically enriched /sup 87/Sr.