Comparison of radiometric and chemical detection sensitivities for heterodyne and direct detection DIAL

Daniel C. Senft; Diego F. Pierrottet

doi:10.1117/12.487326

15 August 2003 Comparison of radiometric and chemical detection sensitivities for heterodyne and direct detection DIAL

Proceedings Volume 5085, Chemical and Biological Sensing IV; (2003) https://doi.org/10.1117/12.487326
Event: AeroSense 2003, 2003, Orlando, Florida, United States

Abstract

A high repetition rate, wavelength agile CO₂ laser has been developed at the Air Force Research Laboratory for use as a local oscillator in a heterodyne detection receiver. Rapid wavelength selection is required for measurements of airborne chemical vapors using the differential absorption lidar (DIAL) technique. Acousto-optic modulators are used in the local oscillator to tune between different wavelengths at high speeds (greater than 100 Hz) without the need for moving mechanical parts. Other advantages obtained by the use of acousto-optic modulators are laser output power control per wavelength and rugged packaging for field applications. A series of experiments to simultaneously characterize the radiometric and chemical detection sensitivities of heterodyne and direct detection DIAL systems is being performed at Kirtland AFB, NM, and will be described. The wvelength agile local oscillator (WALO) has been incorporated into a heterodyne receiver, with the Laser Airborne Remote Sensing (LARS) system providing the laser transmitter and direct detection receiver. The experiment series is studying radiometric issues, spread spectrum operation, the effects of target-induced speckle, and the influence of atmospheric turbulence for both detection mechanisms. Direct comparisons of the heterodyne and direct detection results will be presented, and the results will also be discussed in terms of the implications for fielding operational DIAL systems.

Citation Download Citation

Daniel C. Senft and Diego F. Pierrottet "Comparison of radiometric and chemical detection sensitivities for heterodyne and direct detection DIAL", Proc. SPIE 5085, Chemical and Biological Sensing IV, (15 August 2003); https://doi.org/10.1117/12.487326

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