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Laser Ranging & Detection (LIDAR)
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"A New LIDAR System for the Detection of Cloud and Aerosol Backscatter, Depolarization, Extinction, and Fluorescence",
Franz Immler, Ingo Beninga, Wilfried Ruhe, Bernhard Stein, Bernd Mielke, Soeren Rutz,
Özden Terli, Otto Schrems, Alfred Wegener, Institute for Polar and Marine Research, Bremerhaven, Germany
A newly designed Compact Cloud and Aerosol LIDAR (ComCAL) that was built for the deployment in field campaigns on ground and on mobile platforms like aboard the research vessel Polarstern. The automated system is particularly suited for tropospheric aerosol research within the altitude range from 0.7 to 20 km. As an emitter it uses a frequency doubled and tripled Nd:YAG laser. It measures elastic backscatter and the depolarization at 532 nm and 355 nm as well as inelastic scattering with a 32-channel spectrograph. Recently, it was shown that biomass burning aerosol fluoresces when irradiated by a UV laser beam while other aerosol types do not fluoresce. Beside the detection of N2 and H2O Raman scattering, fluorescence of aerosols can be detected by the new optical set-up of the lidar system. The measurement of wavelength dependent backscatter, extinction, depolarization, and fluorescence makes a detailed study of atmospheric aerosols possible. The new lidar system determines optical properties of aerosols and their vertical distribution. The aerosol types, their origins and abundance can be deduced from that data. These are important parameters for the study of the effect of natural and anthropogenic aerosols on the earth’s climate.
"Development of fluorescence-based LIDAR technology for biological sensing",
Per Jonsson, Fredrik Kullander, Mikael Tiihonen, Melker Nordstrand, Torbjørn Tjærnhage,
Pær Wæterby, Gøran Olofsson, Mikael Lindgren, Materials Research Society Symposium, Volume 883
Copyright ©2005 Materials Research Society
Results for the on-going development of biological warfare agents (BWA) detection systems
based on spectral detection of ultraviolet (UV) laser induced fluorescence (LIF) are presented. A
compact optical parametric oscillator (OPO) with intracavity sum-frequency mixing (SFM) to
generate 293 nm UV laser irradiation was developed. The OPO/SFM device was pumped by a
diode-pumped Nd:YAG laser (1064 nm), including subsequent second-harmonic generation
(SHG) in an external periodically poled KTiOPO4 (PPKTP) crystal. The laser generated 1.8 ns
pulses at 100 Hz with an average power of 44 mW at 532 nm. The whole system could be used to
deliver approximately 30 uJ laser irradiation per pulse (100 Hz) at 293 nm. The spectral detection
part of the system consists of a grating and a photomultiplier tube (PMT) array with 32 channels,
which can measure fluorescence spectra in the wavelength band from 250 nm to 800 nm. The
detector system was designed along with a trigger laser to enable measurement of fluorescence
spectra from an individual aerosol particle of simulants for BWA upon excitation with a single
nanosecond laser pulse. Demonstrated are the successful detection and spectral characterization of
simulants for BWA, i.e., Bacillus atrophaeus (BG), Bacillus thuringiensis (BT), and Ovalbumin
(OA).
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