We have investigated the nonlinear selective reflection of a laser beam (λ = 780 nm) from a high density rubidium vapor. The laser frequency was tuned over atomic transitions and coherent optical excitation of the atomic vapor was realized. The observed narrowing of reflection spectral profile is associated with a competition of two nonlinear processes: optical field induced coherent broadening (Rabi broadening) and optical saturation induced decreasing of dipole–dipole broadening of atomic transitions. For more complete understanding the spectral narrowing we suggest to perform a set of new experiments.
Nonlinear selective reflection from the interface YAG window-high density rubidium vapor in the high-temperature cell is studied at the transition 5S
1/2-5P
3/2. In the experiment tunable pump and probe lasers are used. The selective reflection spectra for the laser probe beam are investigated at four different rubidium atomic densities and five different pump beam intensities. The estimated dipole-dipole interaction-induced line broadening varies from
13.2 to
39.6 GHz, the measured pumped intensities change from
1.2 to
8.8 kW
⋅cm
−2. Growth of the pump intensity causes reduction of the magnitude and the width of the recorded selective reflection resonance. We suggest developing all-optical modulators on the basis of nonlinear selective reflection.
A nonlinear selective reflection from the boundary between a transparent dielectric and dense Rb vapor has been investigated, where the dipole broadening of the 5 S 1/2 –5 P 3/2 working transition is significantly larger than the contribution of the Doppler width. A tunable probe laser and a pump laser with a fixed frequency have been used in the experiment. At a high intensity of pump radiation, a dip has appeared in the reflection spectrum, which splits the spectrum into two symmetric resonances. The splitting value is twice the Rabi frequency. The observation of a narrow structure corresponding to the dressed atomic states opens up additional possibilities for the study of many-particle interactions.