High-resolution sensitive nonlinear laser detection method for chemical analysis based on degenerate four-wave mixing

William M. Tong

doi:10.1117/12.59321

1 May 1992 High-resolution sensitive nonlinear laser detection method for chemical analysis based on degenerate four-wave mixing

William M. Tong

Author Affiliations +

Proceedings Volume 1637, Environmental and Process Monitoring Technologies; (1992) https://doi.org/10.1117/12.59321
Event: OE/LASE '92, 1992, Los Angeles, CA, United States

Abstract

Degenerate four-wave mixing (D4WM) is presented as a simple nonlinear laser method with spectral resolution high enough to resolve isotope/hyperfine lines and detection sensitivity sufficient for sub-ppb or sub-attomole detection in various atomizers and detection cells. Two counterpropagating pump beams and a probe beam are mixed inside the nonlinear medium that consists of analyte atomic or molecular species, and the phase conjugate signal beam is generated as the wavefront-reversed replica of the probe beam. Optical alignment is relatively simple, and optical signal collection is highly efficient since the signal is a laser beam. Continuous sample introduction is possible using an air-acetylene flame as the atomizer. When a relatively low-pressure demountable discharge cell is used as the atomizer, Lorentzian (pressure) broadening is also minimized in addition to cancellation of Doppler broadening. Degenerate four-wave mixing is also effective in detecting trace amounts of analytes in the condensed phase at room temperature using continuously flowing capillary cells that are suitable for interfacing to liquid chromatography and capillary electrophoresis. In addition to pulsed lasers, such as excimer- and Nd:YAG-pumped dye lasers, one can also use relatively low-power continuous-wave lasers such as argon-ion lasers or single-frequency ring dye lasers.

Citation Download Citation

William M. Tong "High-resolution sensitive nonlinear laser detection method for chemical analysis based on degenerate four-wave mixing", Proc. SPIE 1637, Environmental and Process Monitoring Technologies, (1 May 1992); https://doi.org/10.1117/12.59321

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