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9 June 2014 Clipping of TE-CO2 laser pulse using gas breakdown technique for high spatial resolution gas plume detection
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High stability and energy-efficient TE–CO2 laser pulse clipper using gas breakdown techniques for high spatial resolution chemical plume detection is presented. The most dominant time constant, attributed to TE–CO2 unclipped laser pulses, is its nitrogen tail which extends for several microseconds beyond the gain-switched spike. Near-field scattered signal, produced by unclipped laser pulses, interferes with the weak signal backscattered from the long range and far field atmospheric aerosols which ultimately degrades the range resolution of LIDARS to some hundreds of meters. Short laser pulses can be obtained by various techniques such as mode locking, free induction decay, pulse slicing with electro-optic switched. However, output pulses from these require further amplification for any useful application due to their very low energy content. This problem is circumvented in this work by the use of a plasma clipper that achieves high range-resolved remote sensing in the atmosphere. Complete extinction of the nitrogen tail is obtained at pressures extending from 375 up to 1500 Torr for nitrogen and argon gases and approximately 105, for helium. Optimum pressures for helium, argon, and nitrogen, that provide the best stability of the transmitted energy and complete extinction of the nitrogen tail, are identified. Excellent range resolutions can be achieved with TE–CO2 laser-based LIDAR systems. Clipped laser pulses are also field tested.
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Taieb Gasmi "Clipping of TE-CO2 laser pulse using gas breakdown technique for high spatial resolution gas plume detection", Proc. SPIE 9080, Laser Radar Technology and Applications XIX; and Atmospheric Propagation XI, 908012 (9 June 2014);

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