Precision Frequency Measurement of $^{87}$Rb 5$S_{1/2}$ ($F=2$)$\to$5$D_{5/2}$ ($F''=4$) Two-Photon Transition through a Fiber-Based Optical Frequency Comb
1Institute of Quantum Electronics, School of Electronics Engineering and Computer Sciences, Peking University, Beijing 100871 2Jiangsu Key Laboratory on Opto-electronic Technology, School of Physics and Technology, Nanjing Normal University, Nanjing 210046
Abstract：The absolute frequency of $^{87}$Rb 5$S_{1/2}$ ($F=2$)$\to$5$D_{5/2}$ ($F''=4$) two-photon transition at 778 nm is measured in an accuracy of 44 kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of $5.0\times10^{-13}$@1 s is employed for the light source. By using a periodically poled lithium niobate, the femtosecond pulse operating in 1556 nm is frequency-doubled to 778 nm to obtain the direct two-photon transition spectroscopy of thermal rubidium vapor. Through sweeping the carrier envelope offset frequency ($f_{\rm ceo}$), the 5$S_{1/2}$ ($F=2$)$\to $5$D_{5/2}$ ($F''=4$) two-photon transition line is clearly resolved and its absolute frequency is determined via the peak-finding of the fitting curve. After the frequency correction, the measured result agrees well with the previous experiment on this transition. The entire system configuration is compact and robust, providing a potential candidate of optical frequency standard for telecommunication applications.
2016, Vol. 33 
