Optical-field-induced dips and splits in nonlinear spectra of selective reflection from high-density atomic vapor

Journal of Quantitative Spectroscopy and Radiative Transfer. 2026. Vol. 351. Article 109796.

Sautenkov V., Saakyan S., Bobrov A., Zelener B.

We discuss nonlinear spectra of selective reflection from high-density rubidium atomic vapor, where the self-broadening of the resonant transition 5S1/2 - 5P3/2 dominates over the Doppler width. In the experiments, the hole-burning technique with probe and pump lasers is used. The reflection of weak probe beam is investigated at four atomic densities in the range (1.2-3.6) 10^17 cm^−3 and various pump beam intensities. To enhance the spectral resolution, the frequency derivative dR/dnu of the reflection coefficient is analyzed. Increasing the atomic number density changes the character of self-broadening from inhomogeneous to homogeneous. At the highest density, the strong pump field splits the observed spectra into two homogeneously broadened symmetric resonances. The appearance of the optical-field-induced resonances can be explained within the framework of “dressed atomic states” approach. At lower densities the spectral profiles are inhomogeneously broadened. Spectral profiles of the frequency derivative are separated by optically saturated dips. The width of such dips is a combination of the homogeneous component of self-broadening and intensity-dependent field broadening. Careful study of the transition from inhomogeneous to homogeneous broadening may initiate further development of the theory of interatomic interactions in high density atomic gas media.

Keywords: лазерная спектроскопия, Laser spectroscopy, рубидий, rubidium