Nonlinear optical spectroscopy and microscopy

该研究计划将侧重于几种新的非线性光学技术的应用，以研究表面化学，并开发用于高分辨率三维成像和化学成分分析的显微镜。(1)利用红外可见光和频技术研究表面化学许多重要的化学过程发生在气/固或液/固界面。这些接口的研究需要一个工具，具有足够的灵敏度，以探测一个亚单层的分子界面上没有来自气体或液体的干扰。SFG具有优于传统光谱技术（例如IR和拉曼光谱）的若干优点，因为当介质具有反转对称性（例如气体或液体）时，SFG本质上是表面特异性的。它是一种快速发展的技术，对表面化学研究有重大贡献。介绍了极化调制SFG和二维SFG的最新进展，以研究表面化学，包括聚合物的表面相变和电化学催化反应。(2)非线性光学显微镜及其在化学和生物学中的应用 自世纪发明以来，显微镜使科学家们能够看到肉眼看不到的微小结构，并使无数的发现成为广泛的科学领域的基础。非线性光学成像具有优于线性光学成像的若干优点，包括更好的空间分辨率和更好的对比度。我们将开发基于非线性光学过程的显微镜，如相干反斯托克斯拉曼散射（汽车），二次谐波产生（SHG）和三次谐波产生（THG），用于高分辨率成像和化学成分分析。

This research program will focus on applications of several new nonlinear optical techniques to study surface chemistry and to develop microscopy for high-resolution three-dimensional imaging and chemical composition analysis. (1) Study of Surface Chemistry Using IR-visible Sum Frequency Generation (SFG) Many important chemical processes occur at a gas/solid or liquid/solid interface. The study of these interfaces requires a tool that has enough sensitivity to probe a sub-monolayer of molecules on the interfaces without the interference from the gas or liquid. SFG has several advantages over traditional spectroscopic techniques, such as IR and Raman spectroscopy, because SFG is intrinsically surface-specific when the media have inversion symmetry, such as gas or liquid. It is a fast-evolving technique well positioned to have significant contributions to surface chemistry research. New developments in polarization modulation SFG and two-dimensional SFG will be introduced to study surface chemistry, including surface phase transitions of polymers and electrochemical catalytic reactions. (2) Nonlinear Optical Microscopy and Its Applications in Chemistry and Biology      Since their invention in the 16th century, microscopes have allowed scientists to see tiny structures that are not visible to the naked eye and have allowed countless discoveries to be made that have provided underpinnings to broad areas of science. Nonlinear optical imaging has several advantages over linear optical imaging including better spatial resolution and better contrast. We will develop microscopy based on nonlinear optical processes, such as coherent anti-Stokes Raman scattering (CARS), second harmonic generation (SHG), and third harmonic generation (THG), for high-resolution imaging and chemical composition analysis.