Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor

We report measurements of absolute transition frequencies and hyperfine coupling constants for the 8S1/2, 9S1/2, 7D3/2, and 7D5/2 states in ¹³³Cs vapor. The stepwise excitation through either the 6P1/2 or 6P3/2 intermediate state is performed directly with broadband laser light from a stabilized femtosecond laser optical-frequency comb. The laser beam is split, counterpropagated, and focused into a room-temperature Cs vapor cell. The repetition rate of the frequency comb is scanned and we detect the fluorescence on the 7P1/2,3/2→6S1/2 branches of the decay of the excited states. The excitations to the different states are isolated by the introduction of narrow-bandwidth interference filters in the laser beam paths. Using a nonlinear least-squares method we find measurements of transition frequencies and hyperfine coupling constants that are in agreement with other recent measurements for the $8S$ state and provide improvement by $2$ orders of magnitude over previously published results for the $9S$ and $7D$ states.