Subnatural-linewidth laser spectroscopy by phase switching

Abstract
A method to obtain subnatural resolution in laser-induced fluorescence spectroscopy by phase switching is described. The subnatural linewidth is obtained by extracting a coherent transient response induced by the switching of the laser. The linewidth in this type of spectroscopy is determined by the time interval between the switching and observation, instead of the spontaneous lifetime. The result is compared with the experiment on the Na D1 line.