Laser spectroscopy of sub-micrometre- and micrometre-thick caesium-vapour layers *

We present high resolution laser spectroscopy of Cs vapours confined in a unique optical cell of sub-micrometric and micrometric thickness, where a strong spatial anisotropy is pres- ent for the time of interaction between the atoms and laser radi- ation. Similarly to the spectra of selective specular reflection, the Doppler-free spectra of absorption and fluorescence are observed, not revealing cross-over resonances that will be useful for frequency stabilisation, provided the cell is cheap and com- pact. A new resonance in the fluorescence of closed transition is studied, demonstrating its high sensitivity to elastic atom - atom and atom - dielectric surface collisions. The theoretical model- ling performed is in agreement with the experimental observa- tions.