Investigation of Infra Red Spectral Persistence in Condensed Matter

9312381将在硫系玻璃、聚合物和极化铁电材料中研究几种持久的光谱烧孔。三元硫化物玻璃将被用来区分由玻璃拓扑结构控制的过程和由硫化物(主要是Se)化学控制的过程。通过红外皮秒抽运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递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态的影响。将在非常低的温度下研究聚合物，以阻止热激活恢复到振动基态。极化的铁电材料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来研究。在一项相关的研究中，将研究含有缺陷的各种类型的晶体中局域振动模的性质。在这些材料中，局域模式可能被捕获在缺陷位置，导致缺陷吸收光谱在低温下持续变化。当激光入射到玻璃的同一区域时，玻璃对光的吸收可以改变。玻璃保留了激光的记忆。这种记忆效应被称为光谱烧孔，因为对于与激光能量相对应的相同光能，光吸收被精确地降低。研究“光谱空穴”随温度、时间和光能的变化提供了有关玻璃微观结构性质的重要信息。这项拟议的研究将把对这一效应的研究扩展到超短时间尺度和不完美的结晶固体。这类研究的目的是对固体进行改性，以便在室温下观察这些烧孔效应，并将其作为光学存储器件的潜在应用。***

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. ***