SGER: A Difference Frequency Generation Microscope

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

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.