Dynamics of population gratings in NdP5O14crystals

Four-wave mixing signals from transient population gratings established in NdP5O14crystals were analyzed to obtain information on the pumping dynamics and exciton migration characteristics in this material. As the laser pump wavelength is scanned through an Nd³⁺absorption band, the exciton diffusion coefficient is found to vary in a manner consistent with site selection within the inhomogeneously broadened profile. Deviations from simple signal decay patterns are observed whenever the laser is tuned to excited state resonances. In addition, recent theoretical developments are applied to the grating decay data to determine the degree of coherence in the exciton motion.