Microscopic Lensing by a Dense, Cold Atomic Sample

We investigate a micron-scale lensing effect exhibited by a cold, dense sample of $^{87}$Rb atoms and draw parallels with that of a simple convex/concave lens. The experiment is carried out in the fashion of traditional z-scan measurements but in much weaker fields and where close attention is paid to the detuning dependence of the transmitted light. The results are interpreted using numerical simulations and by modeling the atom sample as a thin lens.