title: Active FTIR-based stand-off spectroscopy using a femtosecond optical parametric oscillator.
abstract: We presented the first demonstration of stand-off Fourier transform infrared (FTIR) spectroscopy using a broadband mid-infrared optical parametric oscillator, with spectral coverage over 2700-3200  cm⁻¹. For vapor-phase water and nitromethane (NM), stand-off spectra was recorded using a concrete target at from 1-m to 2-m range and showed good agreement with reference spectra, and in NM a normalized detection sensitivity of 15  ppm·m·Hz(-1/2) was obtained. Spectra from 50-μL droplets of liquid thiodiglycol were detected at a stand-off distance of 2 m from aluminum, concrete and painted metal surfaces. Our results imply that OPO-based active FTIR stand-off spectroscopy is a promising new technique for the detection of industrial pollutants and the identification of chemical agents, explosives or other hazardous materials.
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Zhang
authors.forename: Rhea J
authors.initials: RJ
authors.lastname: Clewes
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Howle
authors.forename: Derryck T
authors.initials: DT
authors.lastname: Reid