Sub-Doppler features of optical processes in the Rb extremely thin cell filled with an additional buffer gas.

International audienceComparison of the resonant absorption and fluorescence in the extremely thin cell (ETC) filled with pure Rb with another one filled with Rb and Neon gas with the pressures 6 Torr and 20 Torr is provided. The effect of the collapse and revival of Dicke-type narrowing is still observable for the thickness L=λ/2, and L=λ, where λ is a resonant laser wavelength 794 nm (D1 line of the Rb), i.e. the spectra of the resonant absorption and fluorescence demonstrate the sub-Doppler narrowing for the thickness L=λ/2 and broadening for the thickness L=λ. It is important to note, that in an ordinary Rb cell with the thickness L in the range of 1mm- 10 cm filled with buffer gas, with a pressure higher than 1 Torr in the Saturation Absorption scheme, any sub-Doppler features are absent. For L= λ the so called velocity selective optical pumping (VSOP) resonance located at the atomic transition is still observable when Ne pressure is 6 Torr , while the linewidth is increased by 4 times in comparison with that obtained in the pure Rb ETC. This VSOP resonance is wash out when Ne pressure is 20 Torr. It is demonstrated that use of the fluorescence spectra at L=λ/2 allows one to use the ETC for the buffer gas pressure measurement. Comparison with the theory is presented