We report on the observation of sub-Doppler resonances on the back-scattered
light from a random porous glass medium with rubidium vapor filling its
interstices. The sub-Doppler spectral lines are the consequence of saturated
absorption where the incident laser beam saturates the atomic medium and the
back-scattered light probes it. Some specificities of the observed spectra
reflect the transient atomic evolution under confinement inside the pores.
Simplicity, robustness and potential miniaturization are appealing features of
this system as a spectroscopic reference.Comment: 6 pages, 4 figure
