Raman spectrometer detects trace chemicals in real time

By using an ordinary green laser pointer, an Israeli team has developed a new Raman spectrometer that can detect extremely minute traces of hazardous chemicals in real time.

According to a statement, the new sensor’s compact design makes it practical for rapid field deployment to disaster zones and areas with security concerns.

Raman spectrometers use highly focused beams of light at precise wavelengths to illuminate small samples of materials.

Very sensitive detectors then study the spectra of light that has been re-emitted, or scattered, by the sample.

Most of this scattered light retains its original frequency or colour, but a very small percentage of that light is shifted ever so slightly to higher or lower wavelengths, depending on the vibrational modes of the sample being studied.

By comparing the shifted and the original wavelengths, it is possible to determine the precise chemicals present in the sample.

The researchers brought this capability down to size by constructing their Raman spectrometer using a low-power, low-cost commercial green laser pointer.

The green laser’s relatively short wavelength helped to improve the detection of the inherently weak Raman signal.

The spectrometer also has the capability to first scan the entire sample optically, sweeping from side to side, to locate individual particles of interest, a task usually performed by Raman microscopes.

‘Since the overall system is modular and compact and can be readily made portable, it can be easily applied to the detection of different compounds and for the forensic examination of objects that are contaminated with drugs, explosives and particularly explosive residues on latent fingerprints,’ said Ilana Bar, a researcher with the Department of Physics at Ben-Gurion University of the Negev in Israel. ‘With proper investment, this system could be deployed quite quickly as a consumer product.’

Other members of the research team include Itamar Malka, Alona Petrushansky and Salman Rosenwaks.

The researchers will present their findings at Laser Science XXVIII — the American Physical Society Division of Laser Science’s Annual Meeting — co-located with the Optical Society’s (OSA) Annual Meeting, Frontier in Optics (FiO), taking place in Rochester, New York, on 18 October.