Investigation of Infra Red Spectral Persistence in Condensed Matter

9312381 Sievers将研究硫属玻璃、聚合物和极化铁电体中的持续光谱烧孔。 三元硫族化物玻璃将用于区分由玻璃拓扑结构控制的工艺与由硫族元素（主要是Se）化学的化学支配的工艺。 分别通过皮秒泵浦探测实验和光子回波实验测量了网络拓扑结构对短时能量传输和均匀退相时间的影响。 这些研究的重点是确定平均配位数对短时动力学的影响。 聚合物将在非常低的温度下进行研究，以抑制热激活恢复到振动基态。 极化铁电体的研究将通过在与晶体极化相反的方向上持续烧孔来重新定向极性分子。 在一个相关的研究中，将研究各种类型的含有缺陷的晶体中局域振动模式的性质。 在这些材料中，局部模式可以被捕获在缺陷位置处，导致在低温下缺陷吸收光谱的持续变化。 %当激光束入射到玻璃的同一区域时，玻璃中的光吸收可以改变。 玻璃对激光有记忆。 这种记忆效应被称为“光谱烧孔”，因为对于与激光能量对应的相同光能，光学吸收精确地减少。 研究“光谱空穴”作为温度、时间和光能的函数提供了关于玻璃微观结构特性的重要信息。 拟议的研究将把这种效应的研究扩展到超短时间尺度和不完美的结晶固体。 这些研究的目的是修改固体，以便在室温下观察这些烧孔效应，作为光学器件的潜在应用。 ***

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. ***