Frequency modulation two-photon spectroscopy with a modelocked laser in laser-cooled Rb

Summary form only given. We have previously demonstrated two-photon spectroscopy using a modelocked laser in samples of laser-cooled /sup 85/Rb and /sup 87/Rb. In this paper we present a mechanism with which to frequency stabilize the probe laser in resonance with the two-photon transition. We show that frequency modulation spectroscopy provides an ideal signal to frequency stabilize the laser to the line center. By modulating at a high frequency one can also work where technical noise in the laser is very low.