Single atom laser: recent experiments

The single-atom microlaser is one and the only type of single atom lasers realized experimentally so far. The gain medium is a beam of excited, non-interacting two-level atoms (/spl lambda/=791 nm, /sup 3/P/sup 1//spl rarr//sup 1/S/sub 0/ transition of /sup 138/Ba) entering an ultra-low loss resonator one at a time. This laser device utilizes the coherent atom-cavity interaction, often referred to as quantized Rabi oscillation, as the light amplification method, With the mean atom number about unity, tens of photons could be stored inside the cavity. The laser oscillation persisted with the mean number of atoms in the cavity well below unity.