Development of Fluorescence-based LIDAR Technology for Biological Sensing
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Development of fluorescence-based LIDAR technology for biological sensing
Per Jonsson,1 Fredrik Kullander,1 Mikael Tiihonen,2 Melker Nordstrand,3 Torbjørn Tjærnhage,3 Pær Wæsterby,3 Gøran Olofsson3 and Mikael Lindgren4,1 1 Swedish Defence Research Agency (FOI), Sensor Technology, PO Box 1165, SE-581 11 Linkoping, Sweden 2 Department of Physics, Royal Institute of Technology, SE-106 91 Stockholm, Sweden 3 Swedish Defence Research Agency (FOI), NBC Defence, SE-901 82 Umeå, Sweden 4 Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway ABSTRACT Results of our 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 µJ 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. We demonstrate the successful detection and spectral characterization of simulants for BWA, i.e., Bacillus atrophaeus (BG), Bacillus thuringiensis (BT), and Ovalbumin (OA).
INTRODUCTION In general, it is difficult to detect hazardous levels of BWA since very low doses of the agents can cause disease for humans. For viral hemorrhagic fevers, less than 10 organisms can cause decease and many of the most dangerous biological agents are infectious when less than 10,000 organisms or spores are inhaled [1]. It is difficult to distinguish harmless bacteria from fatal bacteria, even genetically in some cases. Aromatic amino acids, such as tryptophan, tyrosine and phenylalanine absorb light at 280-290 nm and they fluoresce in a band between 300 nm and 400 nm [2]. Biogenic chemicals associated with cell metabolism, such as reduced nicotinamide adenine dinucleotide (NADH) and riboflavin have their maximum absorption cross-section at around 340 nm and the resulting fluorescence peaks between 450 nm and 560 nm [2]. The route we are pursuing is based on LIF at several excitation wavelengths with spectrally resolved
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detection [3-7]. This method can provide a close to real-time warning and improve the classification of the particles, resulting in a lower degree of false positive alarms. We have previously demonstrated
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