Solid State Ultraviolet Spatial Heterodyne Raman System for Standoff Explosives Detection

Physical Sciences Inc. (PSI), in collaboration with Science and Engineering Services, LLC (SES), proposes to develop a compact solid-state ultraviolet (UV) Raman sensor. The sensor is based on an SES-developed deep UV (234 nm) laser originating from the Laser UV Sources for Tactical, Efficient Raman (LUSTER) DARPA program and a wide field of view, high throughput PSI-developed spatial heterodyne interferometric spectrometer. The 234 nm output of the SES laser will enable the documented advantages of deep UV Raman spectroscopy. The proposed spectrometer is 10,000x more sensitive to Raman photons compared to a slit-spectrometer. Preliminary modeling projects the system will achieve a signal-to-noise ratio of 5 with respect to the 1279 + 1294 cm-1 band of PETN (1 ug/cm2 areal density) while achieving an interrogation rate of 100 mm2 per second, a spectral range of 300-2200 cm-1, and a resolution of 20 cm-1. Initial estimates of the proposed system size, weight, and required power are 0.3 ft3, 17 lbs, and 130 watts, respectively. The Phase I effort will develop a breadboard UV Raman sensor to validate a system model and collect Raman spectra of explosive residues. Requirements and a conceptual design for a Phase II prototype Raman sensor will be generated.