Doppler-free dual-excited state spectroscopy and its application for measurement of hyperfine structure of 6D 5/2 level of 133 Cs

Based on cesium 6S 1/2 —6P 3/2 —6D 5/2 (852 nm + 917 nm) ladder-type system, we simultaneously obtain the Doppler-free saturated absorption spectroscopy (SAS) between the 6S 1/2 → 6P 3/2 transition and optical–optical double resonance (OODR) spectroscopy between the 6P 3/2 → 6D 5/2 transition, when the frequency of 852 nm laser is scanned over the lower transition while keeping the 917 nm laser resonant on the upper transition. The SAS as a frequency scale is used to measure the frequency intervals of hyperfine splitting of the 6D 5/2 excited state via the OODR spectra. With the measured values of hyperfine splitting, the hyperfine coupling constants of the 6D 5/2 state are determined as magnetic dipole A hfs = − 4.60 (5) MHz and electric quadrupole B hfs = 0.23 (47) MHz, which are consistent with previous results. A simple and self-calibration method of measuring the unknown hyperfine structure of an excited state using its own known hyperfine splitting of another state is demonstrated without the aid of any extra frequency calibration tools.