Performance of a GaAlAs laser diode stabilized on a hyperfine component of two-photon transitions in rubidium at 778 nm

The absolute frequency measurement of each hyperfine component of the 5S 3/2 and 5S 5/2 levels in rubidium was done at ENS more than one year ago using Ti-Sa lasers. We built two devices based on diode lasers to study some metrological properties. We measure the frequency differences between hyperfine components of the 5S 5/2 level and we calculate the corresponding hyperfine constants. We also measure the frequency interval between the 5S 3/2 and 5S 5/2 levels using a Schottky diode. The measured stability in terms of Allan variance is 3*10 -13 t -1/2 up to 2000 s. The light shift is investigated and the difference between our two systems is 1.7 kHz. The repeatability of one system is better than 10 -12 and will allow the absolute frequency measurement at this level via the LPTF frequency synthesis chain.