engleski

Influence of femtosecond laser on rubidium D1 resonance lines

A mode-locked femtosecond laser was used to resonantly excite Doppler-broadened rubidium vapor. Resonant excitation of the rubidium atoms by discrete frequency comb optical spectrum results in the comb-like velocity distribution of the excited state hyperfine level populations and velocity-selective population transfer between the Rb ground state hyperfine levels [1, 2, 3, 4]. Modulations in the hyperfine absorption line profiles are observed as a direct consequence of the velocity-selective optical pumping induced by the frequency comb excitation. In the present work, we expand our knowledge about the fs pulse-train excitation of a Doppler-broadened rubidium vapor when the probe laser is tuned to Rb D1 resonance line at 795 nm. In addition, we performed polarization spectroscopy on rubidium atoms in order to investigate the anisotropy of the medium induced by resonant fs pulse-train excitation. The optical pumping process leads to an anisotropic population distribution, and thus to an optically anisotropic medium. The birefringence in medium is induced by a circularly polarized fs pump beam and interrogated with counterpropagated weak cw probe beam. The anisotropy is detected by experimental setup sensitive to the rotation of polarization of the probe beam by tuning the probe laser frequency around the rubidium D1 atomic transitions.

femtosecond laser; frequency comb

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