Subattomole detection in the condensed phase by nonlinear laser spectroscopy based on degenerate four-wave mixing

William M. Tong

doi:10.1117/12.44235

1 July 1991 Subattomole detection in the condensed phase by nonlinear laser spectroscopy based on degenerate four-wave mixing

William M. Tong

Author Affiliations +

Proceedings Volume 1435, Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications; (1991) https://doi.org/10.1117/12.44235
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Laser spectroscopy based on degenerate four-wave mixing (D4WM) has been demonstrated to offer excellent spectral resolution since the signal is inherently Doppler free. When using a low-pressure demountable discharge cell, Lorentzian (pressure) broadening is also minimized. In addition to excellent spectral resolution, this nonlinear laser method also offers excellent detection sensitivity for gas-phase samples. The authors demonstrate that this nonlinear laser method can be used also as a highly sensitive analytical method to detect trace amounts of analyte in the condensed phase using continuously flowing liquid cells at room temperature. Both pulsed lasers and relatively low-power continuous-wave lasers can be used to generate the signal. Since the signal is detected against virtually a dark background and the signal beam is a time-reversed replica of the probe laser beam, optical signal can be most efficiently collected. Condensed phase D4WM detection sensitivity is comparable or better than those of laser-based fluorescence methods and yet D4WM is applicable for detection of both fluorescing and non- fluorescing molecules. Therefore, room-temperature degenerate four-wave mixing has many applications in analytical chemistry, especially when interfaced to continuously flowing chemical separation methods including liquid chromatography and capillary electrophoresis.

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William M. Tong "Subattomole detection in the condensed phase by nonlinear laser spectroscopy based on degenerate four-wave mixing", Proc. SPIE 1435, Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, (1 July 1991); https://doi.org/10.1117/12.44235

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