Standoff Detection of Biomolecules by Ultraviolet Laser-Induced Fluorescence LIDAR

Abstract

Standoff ultraviolet (UV) laser-induced fluorescence (LIF) Light Detection and Range (LIDAR) system has been developed and used for the detection of biological agents/simulants of Bacillus anthracis . The system employs a fiber coupled charge coupled devices spectrometer as sensor. Fourth harmonic (266 nm) of Nd-YAG laser has been used as excitation wavelength. Standoff fluorescence spectra were recorded for biomolecules in aerosol form, in liquid form, and also in solid form adsorbed on surfaces. The signature fluorescence peaks of biomolecules in all forms were dominated by tryptophan peak centered at $\sim 350$ nm. The UV-visible LIF broadband spans between 300 and 500 nm when excitation wavelength 266 nm was used. LIF spectra were recorded with high signal-to-noise ratio (>10) for concentrations down to 10 ppm and from standoff distances up to 100 m. The laser excitation energy dependence of standoff LIF signal was studied.