Doppler-free backward-fluorescence spectroscopy in vapors

A new laser-spectroscopy technique, requiring neither a continuously tunable laser nor a tunable optical transition, is demonstrated. The method involves measuring the fluorescence antiparallel to the laser beam by a scanning Fabry-Perot interferometer. The resulting Doppler-free resomeasurement features a doubled-frequency separation between hyperfine transitions. © 1980, Optical Society of America.