Ellipsometric spectroscopy of rubidium vapor cell at near-normal incidence

Various efforts have been made to overcome Doppler broadening in hyperfine measurement limitations in the atomic vapors spectroscopy and associated applications. The present study measured and calculated hyperfine resolved ellipsometric parameters through the near-normal reflectance spectra of the rubidium vapor cell in two experimental setups based on continuous and modulated pathway. The results indicated that valuable information could be extracted from the ellipsometric parameters about the atomic medium. Change in the ellipsometric parameters in each transition line confirms the existence of the elliptical polarization of the reflected light when it is exposed to the alkali metal vapor. Our results show that the ellipticity at ⁵S_1/2 (F_g = 1, 2) → ⁵P_1/2 (F_e = 1, 2) hyperfine transitions of ⁸⁷Rb (D₁ line) is small, and accordingly hyperfine transitions between the ground ⁵S_1/2 (F_g = 2, 3) and excited ⁵P_1/2 (F_e = 2, 3) states of the ⁸⁵Rb isotope are considerable. These ellipsometric parameters, as phase difference, can trace the behavior of the relative orientation of the electric field and atom velocity in the interface based on van der Waals dipole-dipole interaction and is directly proportional to the strength of the light-matter interaction which extremely useful instead complicated atomic spectroscopic methods.