A solid-state deep ultraviolet spatial heterodyne Raman system for standoff chemical detection

Abstract

There is an on-going need for sensor technologies capable of providing non-contact chemical detection and identification in the defense community. Here, we present the development of a standoff deep ultraviolet (DUV) Raman sensor for the detection of explosive residues. The sensor is based on a solid-state DUV excitation source coupled with a Spatial Heterodyne Spectrometer (SHS) receiver. The sensor is designed to detect Raman signals from a 4 cm2 area surface at a 1 m standoff. Detection and identification is achieved by correlating measured Raman signatures with high fidelity library spectra. The DUV excitation enables operation in a solar blind spectral region, leverages v4 cross section scaling and resonance enhancement of Raman signatures, and minimizes the impact of sample fluorescence. The SHS receiver provides a ~1000× higher etendue than conventional slit-based spectrometers in a compact and rugged form factor, allowing for high performance field use. This work describes the system design and architecture of the Raman sensor prototype. Developmental standoff Raman measurements with the sensor using bulk liquid and solid samples are presented. Traceability to detection at the μg/cm2 scale is demonstrated and future improvements to increase system standoff are discussed.