Friday, October 28, 2011
Hall 1-2 (San Jose Convention Center)
Multi-photon laser wave-mixing spectroscopy is presented as an unusually sensitive optical absorption-based detection method for trace analytes in micrometer-thin cells. In a wave-mixing setup, two laser beams are focused and mixed to create dynamic gratings inside the analyte. The incoming photons are scattered off these gratings to create a signal beam that is characteristic of the analyte. The wave-mixing signal has a quadratic dependence on analyte concentration, and hence, small changes in analyte properties result in more dramatic changes in the signal. The signal also has a cubic dependence on laser power, and hence, one can use low-power compact solid-state lasers that are much safer and more portable for field use. Currently available methods, including fluorescence methods, do not offer sensitivity and specificity levels needed for trace analysis of biomolecules related to diseases. Since the wave-mixing signal is a coherent laser-like beam with its own propagation direction, the background noise is minimal and the signal-to-noise ratio is excellent. Wave mixing offers sensitive detection of biomolecules in their native form without labels and probes, and convenient detection of chem/bio agents in microchannels, microarrays, microchips and microfluidic systems. Wave mixing also allows detection of explosives, such as trinitrotoluene or triacetone triperoxide and other hazardous chemicals such as environmental toxins at trace-concentration levels. Using compact low-power lasers, wave mixing is demonstrated as a novel field deployable detection system for a wide range of chem/bio agents that offers standoff detection capability and parts-per-quadrillion level detection sensitivity.