Standoff detection via single-beam spectral notch filtered pulses

Abstract

We demonstrate single-beam coherent anti-Stokes Raman spectroscopy (CARS), for detecting and identifying traces of solids, including minute amounts of explosives, from a standoff distance (>50 m) using intense femtosecond pulses. Until now, single-beam CARS methods relied on pulse-shapers in order to obtain vibrational spectra. Here we present a simple and easy-to-implement detection scheme, using a commercially available notch filter, that does not require the use of a pulse-shaper.

Detecting micro-particles of explosives at ten meters using selective stimulated Raman scattering

“…Previously, coherent anti-Stokes Raman scattering, was used for standoff detection [4], and recently detected small quantities at 50 meters with a 6 inch optic [5]. With a similar solid angle of collection, SB-SRS can detect four orders of magnitude less material in two orders of magnitude less time.…”

Review of explosive detection methodologies and the emergence of standoff deep UV resonance Raman

“…Several studies have investigated using nonlinear Raman methods such as coherent anti‐Stokes Raman spectroscopy (CARS) for standoff explosives detection . CARS is a nonlinear technique that traditionally utilizes two laser beams to excite a sample.…”

“…Bremer et al recently constructed a single‐beam CARS raster‐scan imaging spectrometer that was used to measure multispectral images of DNT at µg/cm 2 concentrations at 1 m . Natan et al developed a single‐beam CARS spectrometer that could measure analytes such as nitrate, urea, and RDX from 12 to 50 m away using a 19 cm lens . The authors demonstrated that RDX could be detected at 24 m with a 3 s accumulation time.…”

Stimulated Raman spectroscopy with 0π pulses

“…Thus the technique can be applied to media with strong multiple scattering. Let us note here that a similar technique has been suggested by using spectral-notch-filtered pulses in CARS demonstrated in [13], which allows researchers to obtain a signal with a signal-shaped pulse. Because of the behavior of the hole-filling signal with respect to one-and two-photon detuning, the technique has higher tolerance to background molecules and has the potential to detect a relatively small fraction of molecules among a vast amount of background.…”