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Laser-induced luminescence (LIL) is the emission of light resulting from absorption of laser energy by a substance. Reradiated light contains a major component at the wavelength of the exciting laser light (reflected light); however, there are also many new wavelengths (luminescence) that are determined primarily by the electronic structure of the substance. 

LIL includes both laser-induced fluorescence (LIF), which is fast luminescence occurring on time scales of the order of several nanoseconds, and laser-induced phosphorescence (LIP), which is slower luminescence occurring on time scales as long as several seconds. The luminescence spectrum is not only a function of time, but also a function of the excitation spectrum.

Fluorescence and phosphorescence have been studied for a number of years and have been used in numerous ways in the laboratory environment. LIL is finding widespread use in many new and diverse applications, for example:

• to study energy redistribution collisions in vapors

• for fingerprint detection

• to map flowfields in chemical lasers.

In recent years, advances in laser technology have increased reliability and portability of lasers and also significantly reduced costs, readily demonstrated by the wide use of helium-neon lasers in bar-code scanners found in supermarkets.

Quantitative measurements show there is sometimes a very strong correlation between LIL and some physical characteristic of the material; many times this correlation is because fluorescence reveals relationships between molecular functional groups, such as conjugation. (This is in contrast to infrared-absorption techniques, which are mainly used to reveal presence of individual molecular functional groups.) Because relationships between certain molecular functional groups are altered during degradation, LIL can be used to monitor these processes. Furthermore, these approaches can be adapted to a processing environment.

For more information about laser-induced reactions to measure product quality capabilities at SwRI or how you can contract with SwRI, please contact Todd Goyen at tgoyen@swri.org or (210) 522-3528.
 

| Department of Electromechanical and Optical Systems | Applied Physics Division | SwRI Home |

Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

August 05, 2008