CAVITY QED WITH HIGH-Q WHISPERING-GALLERY MODES

We report measurements of cavity-QED effects for the radiative couplin g of atoms in a dilute vapor to the external evanescent field of a whi spering-gallery mode (WGM) in a fused silica microsphere. The high Q ( 5 x 10(7)), small mode volume (10(-8) cm(3)), and unusual symmetry of the microcavity evanescent field enable velocity-selective interaction s between fields with photon number of order unity in the WGM and (N) over bar(T) similar to 1 atoms in the surrounding vapor.