Remote Raman Spectroscopic Detection of Inorganic, Organic and Biological Materials to 100 m and More

Abstract

We have designed and tested a portable gated‐Raman system that is capable of detecting organic and inorganic bulk chemicals over stand‐off distances of 100 m and more during day and night time. Utilizing a 532 nm laser pulse (∼35 mJ/pulse), Raman spectra of several organic and inorganic compounds have been measured with the portable Raman instrument over a distance of 100 m. Remote Raman spectra, obtained with a very short gate (2 micro second), from a variety of inorganic minerals such as calcite (CaCO3), α‐quartz (α‐SiO2), barite (BaSO4), and FeSO4⋅7H2O, and organic compounds such as acetone, methanol, 2‐propanol and naphthalene showed all major bands required for unambiguous chemical identification. We also measured the Raman and fluorescence spectra of plant leaves, tomato, and chicken eggshell excited with a 532 nm, 20 Hz pulsed laser and accumulated over 200 laser shots (10‐s integration time) at 110 m with good signal‐to‐noise ratio. The results of these investigations show that remote Raman spectroscopy over a distance of 100 m can be used to identify Raman fingerprints of both inorganic, organic, and some biological compounds on planetary surfaces and could be useful for environmental monitoring.