Nonlinear laser wave-mixing spectroscopy is presented as an ultrasensitive detection method for chemical and biological agents in thin-film, gas- and liquid-phase samples. Wave mixing is an unusually sensitive absorption-based detection method that offers inherent advantages including excellent sensitivity, small sample requirements, short optical path length, high spatial resolution and excellent standoff detection capability. Wave mixing offers excellent optical absorption detection sensitivity even when using thin samples (<0.1 mm), and hence, it is inherently suitable for interfacing to microarrays, microfluidics, chip-based capillary electrophoresis and other liquid- and gas-phase flow systems. The wave-mixing signal is generated instantaneously as the two input laser beams intersect inside the analyte of interest. Wave-mixing detection can be used in both transmitted and reflected modes to detect chem/bio agents on surfaces. Laser excitation wavelengths can be tuned to detect multiple chem/bio agents in their native form. Since the wave-mixing signal is a coherent laser-like beam with its own propagation direction, it offers excellent S/N and allows remote standoff detection capability. The sensitivity of this laser detection technique has reached levels in the parts-per-quadrillion range. These sensitivity levels have been optimized for detection of nitroaromatic compounds and proteins. Nitroaromatic explosives are detected here by excitation at 266 nm and can be separated using capillary electrophoresis with excellent sensitivity and resolution. Tunable mid-infrared quantum cascade lasers have also been used in these studies to specifically detect TATP using wave mixing.

Detection of chemical agents using nonlinear laser wave mixing spectroscopy

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.