Recent Trends in Laser-Based Standoff Detection of Hazardous Molecules

We report here recent developmental studies in the field of laser-based standoff detection of hazardous molecules. We summarize the most important recent advances in the fields of (i) Raman spectroscopy (ii) LIBS (iii) LIF (iv) QCL/EC-QCL-based infrared (v) photoacoustic spectroscopy and (vi) THz spectroscopic/imaging studies especially towards the detection of hazardous materials and that too in standoff configurations. With the improvements in the technology of laser sources, sensors/detectors the standoff techniques have evolved rapidly in the last few years. From small range and limited detectable compounds with low sensitivity, limited only to laboratory conditions, to wide range of compounds and high sensitivity along with open atmosphere long range and range adaptable scenarios are thoroughly discussed. We account here the different lasers used and distances at which the signatures of various molecules were identified. Finally, a roadmap is chalked out taking into account the strengths of each of these techniques.