Absolute frequency measurement of the cesium D₂ line

We describe a scheme of absolute frequency measurement of the cesium-stabilized diode laser at 852 nm based on the absolute frequency standard of ⁸⁷Rb at 780 nm and well stabilized CO₂ laser at 9.23 μm. The frequency of the CO₂ laser is stabilized to the center of the 4.3-μm saturated fluorescence with frequency instability of 5 kHz. Two diode lasers are stabilized to the center of D₂ saturated absorption line of Cs at 852 nm and to the center of D₂ line of ⁸⁷Rb at 780 nm with accuracy about 30 kHz, respectively. The sum frequency of the 852 nm and 9.23 μm radiation is beated against the 780 nm radiation to obtain the absolute frequency of the Cs D₂ line. The sum-frequency generation and beat frequency experiment will be finished in the near future and reported in the conference.