A novel absorption resonance for atomic clocks

Abstract

We report an experimental study of an all-optical three-photon-absorption resonance (known as an "N-resonance") and discuss its potential application as an alternative to atomic clocks based on coherent population trapping (CPT). We present measurements of the N-resonance contrast, width and light shift for /sup 87/Rb under various conditions including both D/sub 1/ and D/sub 2/ optical transitions. Under conditions such that first-order light shifts cancel, we observe promising short-term frequency stability (/spl sim/ 1.5 /spl times/ 10/sup -11/ /spl tau//sub - 1/2 /) for an N-resonance on the Di transition of /sup 87/ Rb vapor.