New Mechanism for the Production of Optical Resonances with Subnatural Linewidths

Abstract
Optical resonances with subnatural linewidth as narrow as 2.6 MHz have been observed with excellent signal-to-noise ratio in the Na D1 line (natural width 10 MHz) in a polarization spectroscopy experiment. The new, subnatural resonances arise from Zeeman coherences which are produced by a strong probe beam and destroyed by a velocity-selective optical Hanle effect.