Fluorescence removal from raman spectra by polarization subtraction

An apparatus for non-destructively interrogating a substance from a distance for at least one chemical constituent comprising:

• a. a laser source generating directed, polarized laser energy in the UV wavelength range;
• b. a receiver having components for collecting Raman scattering of the source parallel and perpendicular to the source polarization and generating signals correlated to the parallel and perpendicular collected polarizations;
• c. a processor having an input for the signals;
• d. software for signal acquisition, data processing and material detection to
• i. combine the collected parallel and perpendicular polarizations;
• ii. generate a signal representative of the combination;
• iii. determine if the content of the combination is indicative of a chemical constituent.

A system for standoff distance interrogation of an unknown sample comprising:

• (a) a hand-held instrument including:
• (i) a polarized UV laser source to generate an interrogating laser beam to standoff distances, and
• (ii) a collector of return light from the interrogation, and a polarizer of the return light that can be adjusted between different polarization states;
• (b) a portable spectrometer operatively connected to the hand-held instrument and adapted to receive spectra of the return light, each polarized in a different polarization state;
• and
• (c) a portable computer operatively connected to the spectrometer and adapted to quantify and compare the spectra, the comparison used to remove fluorescence and better distinguish Raman information to more accurately detect constituent chemicals in the return light.