SGER: A Difference Frequency Generation Microscope

化学系的分析和表面化学项目将通过探索性研究（SGER）小额资助支持俄亥俄州立大学Heather Allen教授的研究项目。这项工作的目标是开发一种新的方法，能够利用振动二阶光谱成像液体表面。虽然红外和拉曼显微镜是固体表面成像薄膜的好工具，但使用振动差频（或和频）显微镜的非线性技术为气液界面成像提供了显着更高的灵敏度。目前，从液体表面获取光谱主要采用和频光谱法；然而，由于技术的复杂性，和频成像还远未普及。Allen教授和她的学生将利用红外显微镜技术作为光学平台来设计差频显微镜。在这项高风险高影响的研究中需要测试的假设是，将高重复率的红色激光与连续波红外源相结合，将产生少量的差频光子，这些光子可以通过仔细优化检测变量进行成像。另外，利用高重复率的红外光源与红色激光脉冲相结合，将提供大量的光子，可以更容易地使用红外显微镜平台成像。这种具有分子选择性和高灵敏度的差频显微镜将应用于生物、材料、环境和大气气溶胶的成像研究。

The Analytical and Surface Chemistry program in the Division of Chemistry will support the research program of Prof. Heather Allen of Ohio State University through a small grant for exploratory research (SGER). The goal of this work is to develop a new method with the capability to image liquid surfaces using vibrational second-order spectroscopy. While infrared and Raman microscopy are well utilized tools for imaging films on solid surfaces, nonlinear techniques using vibrational difference-frequency (or sum-frequency) microscopy provides markedly greater sensitivity for imaging the air-liquid interface. Currently, sum frequency spectroscopy is used to obtain spectra from liquid surfaces; however, sum-frequency imaging is far from being commonplace mainly because of technical complexity. Prof. Allen and her students will utilize infrared microscope technology an optical platform for the design of a difference-frequency microscope. The hypothesis to be tested in this high risk high impact study is that combining a high repetition rate red laser with a continuous wave infrared source, will generate a small number of difference-frequency photons that could be imaged with careful optimization of detection variables. Alternatively, utilizing a high repetition rate infrared source combined with red laser pulses will provide a large number of photons that can more easily be imaged using the infrared microscope platform. This molecularly selective and highly sensitive difference-frequency microscope will have application to imaging in biology, materials, and environmental and atmospheric aerosol research.