Nonlinear optical spectroscopy and microscopy

这项研究计划将重点放在几种新的非线性光学技术在研究表面化学和发展用于高分辨率三维成像和化学成分分析的显微镜方面的应用。(1)红外可见和频(SFG)表面化学研究许多重要的化学过程发生在气/固或液/固界面上。对这些界面的研究需要一种具有足够灵敏度的工具来探测界面上的亚单分子层，而不受气体或液体的干扰。与红外和拉曼光谱等传统光谱技术相比，SFG有几个优势，因为当介质具有反转对称性时，SFG本质上是表面特定的，例如气体或液体。这是一项快速发展的技术，很有可能对表面化学研究做出重大贡献。将介绍极化调制SFG和二维SFG的新进展，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16世纪发明以来，显微镜使科学家能够看到肉眼看不到的微小结构，并做出了无数的发现，为广泛的科学领域提供了基础。与线性光学成像相比，非线性光学成像具有更高的空间分辨率和更好的对比度。我们将发展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(CARS)、二次谐波(SHG)和三次谐波(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.