Sub-Doppler Spectroscopy of Room-Temperature Cs Atomic Vapor in a 400-nm-Thick Nanocell

Thesub-Doppler absorption and fluorescence spectra at the frequencies of D-1- and D-2-line transitions in Cs atomic vapor, enclosed in a nanocell (NC) with a thickness L similar to 400 nm, have been investigated experimentally at a near-room temperature. It is shown that a decrease in the NC temperature to 35 degrees C causes narrowing of the absorption lines to values smaller than the Doppler width by a factor of 6, due to which the strong spectral broadening induced by laser field can be measured. The high intensity threshold for optical pumping (which limits the fluorescence intensity in centimeter-length cells) made it possible to record fluorescence spectra (using laser power of several milliwatts) at a temperature of 20 degrees C; thus, a frequency marker of transitions in the range of D-1,D-2 lines can be developed based on a room-temperature NC. A comparison with a widely used marker based on saturated absorption is performed.