Paper: 2013 Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser

Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser

Reviews and Highlights Quantum Science Molecular and Soft-matter Ultrafast Nano-optics and Nanophotonics Mineralogy and Geochemistry

Ian M. Craig, Matthew S. Taubman, A. Scott Lea, Mark C. Phillips, Erik E. Josberger, and Markus B. Raschke
Optics Express 21, 30401 (2013)
DOI PDF

Utilizing a broadly-tunable external cavity quantum cascade laser for scattering-type scanning near-field optical microscopy (s-SNOM), we measure infrared spectra of particles of explosives by probing characteristic nitro-group resonances in the 7.1-7.9 μm wavelength range. Measurements are presented with spectral resolution of 0.25 cm−1, spatial resolution of 25 nm, sensitivity better than 100 attomoles, and at a rapid acquisition time of 90 s per spectrum. We demonstrate high reproducibility of the acquired s-SNOM spectra with very high signal-to-noise ratios and relative noise of <0.02 in self-homodyne detection.