9312381 Sievers Persistent spectral hole burning will be investigated in chalcogenide glasses, polymers, and poled ferroelectrics. A ternary chalcogenide glass will be used to distinguish processes which are controlled by the glass topology from those which are dominated by the chemistry of the chalcogen (primarily Se) chemistry. The influence of network topology on short time energy transfer and the homogeneous dephasing time will be measured by infrared picosecond pump-probe and photon echo experiments, respectively. The focus in these studies is to determine the effect of the average coordination number on the short time dynamics. Polymers will be investigated at very low temperatures to inhibit thermally activated recovery to the vibrational ground state. Poled ferroelectrics will be studied by reorienting the polar molecules by persistent hole burning in the opposite direction to the crystal polarization. In a related study, the nature of localized vibrational modes will investigated in various types of crystals containing defects. In these materials localized modes may be trapped at a defect site leading to persistent changes in the defect absorption spectrum at low temperatures. %%% The absorption of light in a glass can be altered when a laser beam is incident on the same region of the glass. The glass retains a memory of the laser light. This memory effect is termed "spectral hole burning" because the optical absorption is reduced precisely for the same light energy corresponding to the laser energy. Study of the "spectral hole" as a function of temperature, time and light energy provides important information about microscopic structural properties of the glass. The proposed study will extend the investigation of this effect to ultrashort time scales and to imperfect crystalline solids. The aim of such studies is to modify a solid in order to observe these hole burning effects at room temperature with the potential application as optical mem ory devices. ***
