Absolute two-photon cross section of Rb measured by differential absorption

Abstract

We applied a simple, sensitive differential absorption technique to measure the two-photon cross section for the 5(2)S((1/2))(F(g) = 2) ? 5(2)D(5/2)(F(e) = 4) hyperfine transition in (85)Rb [sigma((2)) = (1.2 +/- 0.5) x 10(-18) cm(4)/W]. The detection circuit permitted straightforward measurements close to the shot-noise limit. Detailed quantitative analysis of the measurements shows excellent agreement with theory.