3 October 2007 New concept design of differential absorption lidar: fusion of DIAL and TDLS methods
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We propose a new approach to range-resolved remote gas sensing in the atmosphere based on a combination of a DIAL and tunable-laser diode spectroscopy (TDLS) methods. To add range-resolving capabilities to a TDLS sensor we propose to arrange a group of retroreflectors (RRs) dividing an absorption path into adjacent measurement sections similar to those utilized by conventional DIAL systems. We implemented two techniques for the interrogation of the RRs: 1) scanning a beam of a continuous-wave laser over RRs sequentially; 2) using a time delay between returns from different RRs illuminated with a pulsed laser. We employed scanning technique with a vertical-cavity surface-emitting laser (VCSEL) operating near 1389 nm. A single-pulse interrogation method was demonstrated with a 10.9-&mgr;m quantum cascade laser (QCL) suitable for detection of ammonia, ethylene and water vapor in the atmosphere. Gas sensing and ranging was performed over distances varying from ~ 1 m up to ~ 1 km. Using VCSEL we attained a 0.5-s time resolution in gas concentration profiling with a 10-cm spatial resolution. Minimum interrogation time of a group of RRs was ~ 9 ms. A new generation of differential absorption LIDARs can be developed for range-resolved gas sensing in the atmosphere over distances up to ~ 1 km. The instruments can be used for a variety of applications ranging from fencing industrial areas to monitor fluxes of atmospheric pollutants to continuous air quality control in populated areas
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Alexandre Lytkine, Brian Lau, Alan Lim, Wolfgang Jaeger, John Tulip, "New concept design of differential absorption lidar: fusion of DIAL and TDLS methods", Proc. SPIE 6750, Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing III, 67500C (3 October 2007); doi: 10.1117/12.737436; https://doi.org/10.1117/12.737436

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