Underwater Time-Gated Standoff Raman Sensor for In Situ Chemical Sensing

We describe the fabrication of an underwater time-gated standoff Raman sensor, consisting of a custom Raman spectrometer, custom scanner, and commercial diode-pumped pulsed 532 nm laser all located inside a pressure housing. The Raman sensor was tested in the laboratory with samples in air, a tank containing tap water and seawater, and in the coastal Hawaiian harbor. We demonstrate our new system by presenting standoff Raman spectra of some of the chemicals used in homemade explosive devices and improvised explosive devices, including sulfur, nitrates, chlorates, and perchlorates up to a distance of similar to 6m in seawater and tap water. Finally, the Raman spectra of these hazardous chemicals sealed inside plastic containers submersed in the Hawaiian Harbor water are also presented.

Automated summary

This study introduces the fabrication of an underwater time-gated standoff Raman sensor and demonstrates its capabilities in detecting hazardous chemicals in seawater and tap water samples up to a distance of 6m, as well as in plastic containers submerged in Hawaiian Harbor water. The sensor combines a custom Raman spectrometer, custom scanner, and commercial diode-pumped pulsed 532 nm laser housed in a pressure housing, showing potential for remote chemical detection applications.