A Novel Laser Technique for Observing Optical Coherence in Gases, Molecular Beams, and Solids

Abstract

Traditionally, the phenomenon of optical coherence has been observed by detecting coherent transients (i.e., optical nutation, FID, photon echoes) propagating along the laser beam following passage through an absorbing medium. Recently, we have demonstrated that detection of the incoherent (spontaneous) emission from selectively prepared states provides the optical coherence of the ensemble. Our observation of the nutation and the photon echo at right angles to the exciting beam gives directly optical T_1, T_2, and the moment of the laser excited transition. This technique is simple and not susceptible to some of the problems inherent in coherent absorption experiments. Details about this laser technique will be presented. We will also discuss the different dynamical information one obtains about excited states in gases, molecular beams and solids.