Fluorescência ressonante de dois fótons em vapor de rubídio com lasers pulsado e contínuo

Abstract

In this work we study a resonant fluorescence signal generated by two-photon absorption in rubidium vapor, when the atomic system interacts with a continuous wave laser from a diode laser beam and one ultrashort pulse train from a femtosecond Ti:sapphire laser, in the ladder transition 5S1/2 -> 5P3/2 -> 5D5/2. The atoms contained in a closed and heated cells interact with the pair of laser beams in a co-propagating con guration. The laser beams have wavelengths of about 780 nm and linear and parallel polarization. We analyze the fluorescence signal detected forward, in the same direction of the incidence laser beams, as well as in the direction perpendicular to lasers ( fluorescence at 90º). We analyze the fluorescence signal at 421 nm generated by the spontaneous decay of the excited state 6P3/2 to the ground state 5S1/2 of rubidium, as a function of the many parameters of the system, such as: the signal polarization with respect to the polarization of the laser beams, the frequency and the intensity of the diode laser, and the atomic density of the sample. We observed saturation e ects on the fluorescence detected signal varying the intensity of the laser diode and the atomic density. E ects of an optical pumping from the diode laser beam on the fluorescence signal were observed and explained with a simple theoretical model.