A new portable Raman spectrometer created using an ordinary green laser pointer can detect minute traces of explosives and other hazardous chemicals in real time.
Raman spectrometers rely on highly focused light beams at precise wavelengths to illuminate small samples of materials. Very sensitive detectors then study the sample's scattered spectra. Most of the re-emitted light retains its original frequency, but a small percentage is slightly shifted to higher or lower wavelengths, depending on the sample's unique vibrational modes. Comparing the shifted and original wavelengths enables determination of the precise chemicals in the sample.
Schematic of the Raman spectrometer, including a laser pointer, dichroic mirror, prism, objective, X-Y motorized translational stage, long-wave pass edge filter, lens and a detector (spectrometer/intensified charge-coupled device).
Developed by scientists at Ben-Gurion University of the Negev, the laser pointer-based spectrometer scans entire samples optically to locate individual particles of interest &mash; a task previously performed by cumbersome Raman microscopes. The laser's relatively short wavelength helps improve detection of the inherently weak Raman signal, and the spectrometer's compact design is suitable for rapid field deployment to disaster zones and other security-deficient areas.
"Since the overall system is modular, compact and can be readily made portable, it can be easily applied to the detection of different compounds and for forensic examination of objects that are contaminated with drugs, explosives and particularly explosive residues on latent fingerprints," said Ilana Bar of the university's Department of Physics. "With proper investment, this system could be deployed quite quickly as a consumer product."
The research will be presented Oct. 18 at Laser Science XXVIII, the American Physical Society Div. of Laser Science's annual meeting, which is collocated with OSA's annual meeting, Frontiers in Optics, in Rochester, N.Y.