High-Resolution Rb Two-Photon Transition Spectroscopy by a Femtosecond Frequency Comb via Pulses Control**Supported by the National Basic Research Program of China under Grant No 2012CB921603, the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China under Grant No IRT13076, and the National Natural Science Foundation of China under Grant Nos 61378049, 10934004, 11404198,

Abstract

We experimentally observe the high resolution direct frequency comb spectroscopy using counter-propagating broadband femtosecond pulses on two-photon transitions in room-temperature 87Rb atoms. The Doppler broadened background is effectively eliminated with the pulse shaping method and the spectrum modulation technique. The combination of the pulse shaping method and the spectra modulation technique provides a potential approach to reduce background of at least 99%.