Structure-Property Relations for Nonlinear Optical Materials

计划对材料的结构/非线性光学性质关系进行积极的研究，特别是对几类有机化合物。在这一领域已经组建了一支优秀的协作专家团队，以及用于非线性光学(NLO)材料表征的最好的实验设备。除了CREOL的PI包括一名化学家外，合作者还包括亚利桑那大学化学系的Seth Marder、Joseph Perry和Jean-Luc Bredas，苏黎世ETH的Francois Diederich，Olga Przhonska，Alex Kachkovski以及乌克兰基辅国家科学院物理研究所的同事，以及佛罗里达大学的Anthony Brennan。最先进的实验室设施是专门为该提案中概述的计划而设计和开发的。五个实验室致力于这项调查。最新增加的是一个飞秒泵浦/连续介质探测器，非线性“分光光度计”。它模仿了标准的线性分光光度计的操作，是最接近可被制成商业仪器的设施，用于非线性光学材料性质的光谱分析。数据与双光子荧光(2PF)光谱方法一致，该方法需要相当长的时间，需要荧光样本。因此，可以研究更广泛的材料。这些技术与PI先前开发的实验性Z扫描技术，以及单频泵浦-探测方法与飞秒、皮秒和纳秒可调谐光学参数源的补充方法相结合，为实现这一拟议工作的目标提供了一种独特的工具。这项研究的最终目标是开发一种根据线性光学性质和/或分子结构来预测非线性光学性质的能力，类似于PI对半导体所完成的工作。飞秒连续谱的波长范围从300纳米到1.7毫米，因此可以在这个宽广的光谱范围内探测NLA。因此，在一个单独的实验中，测量了从IR到UV的所有频率下的吸收变化。通过时间延迟探测，还得到了这种非简并NLA的动力学特性。这使得双光子吸收的超快NLA过程很容易从诸如激发态吸收的累积非线性中分离出来。用这台仪器可以确定强双光子吸收带在哪里，激发态吸收光谱是什么。这些问题和类似问题的答案将为理论家提供必要的信息，以检验理论和实践者寻找和利用新的NLO材料。

An aggressive investigation is planned on the structure/nonlinear optical property relations of materials with special emphasis on several classes of organic compounds. An excellent collaborative team of experts has been assembled in this area along with the best experimental facilities for nonlinear optical (NLO) materials characterization. Along with the PI's at CREOL including a chemist, collaborators include Seth Marder, Joseph Perry and Jean-Luc Bredas with Chemistry at the University of Arizona, Francois Diederich in Chemistry at ETH, Zurich, Olga Przhonska, Alex Kachkovski and co-workers at the Institute of Physics, National Academy of Sciences, Kiev, Ukraine, and Anthony Brennan at the University of Florida. State-of-the-art laboratory facilities have been specifically designed and developed for the program outlined in this proposal. Five laboratories are devoted to this investigation. The latest addition is a femtosecond pump/continuum probe, nonlinear "spectrophotometer". This mimics the operation of a standard linear spectrophotometer and is the closest one can come to a facility that could be made into a commercial instrument for spectral analysis of NLO material properties. Data are consistent with the two-photon fluorescence (2PF) spectroscopy method, which takes considerably longer and requires fluorescent samples. Thus, a broader range of materials can be studied. These techniques, combined with the PIs' previously-developed experimental Z-scan technique, along with complementary methods of single frequency pump-probe methods with femtosecond, picosecond, and nanosecond tunable optical parametric sources, provide a unique facility to carry out the goals of this proposed effort. The ultimate goal of this study is to develop a predictive capability for the NLO properties in terms of the linear optical properties and/or molecular structure similar to what the PIs have accomplished for semiconductors. The femtosecond continuum can range in wavelength from 300 nm to 1.7 mm and can thus probe the NLA over this broad spectral range. Thus, in a single experiment the changes in absorption at all frequencies from the IR to the UV are measured. By temporally delaying the probe, the dynamics of this nondegenerate NLA are also obtained. This allows easy separation of the ultrafast NLA process of two-photon absorption from cumulative nonlinearities such as excited state absorption. With this instrument one can determine where are the strong two-photon absorption bands, and what is the excited-state absorption spectrum. The answers to these and similar questions will give theoreticians the information necessary to test theories and practitioners to find and exploit new NLO materials.