Noninvasive deep Raman detection with 2D correlation analysis

• Depth-dependent spatially offset Raman spectra are analyzed using generalized 2D correlation spectroscopy (2DCOS).
• 2DCOS analysis gives the resolved spectral components and their sequential order.
• Linear shaped illumination is employed to reduce the potential photo-damage.

The detection of poisonous chemicals enclosed in daily necessaries is prerequisite essential for homeland security with the increasing threat of terrorism. For the detection of toxic chemicals, we combined a sensitive deep Raman spectroscopic method with 2D correlation analysis. We obtained the Raman spectra from concealed chemicals employing spatially offset Raman spectroscopy in which incident line-shaped light experiences multiple scatterings before being delivered to inner component and yielding deep Raman signal. Furthermore, we restored the pure Raman spectrum of each component using 2D correlation spectroscopic analysis with chemical inspection. Using this method, we could elucidate subsurface component under thick powder and packed contents in a bottle.