Friday, October 28, 2005
1:00pm – 2:00pm
Professor
Philip Varghese
ASE-EM
Department
The
University of Texas at Austin
“Filtered Light Scattering Measurements using Diode Lasers”
Abstract:
I will describe two measurement techniques based on scattering of near-infrared diode laser radiation. In both cases we exploit the tunability of diode lasers to accomplish the measurement. Diode lasers have other properties that make them desirable as a basis for sensors in practical applications – they are small, rugged, and reliable, and relatively inexpensive. Elastic light scattering (Rayleigh scattering) is used to measure gas velocity. Inelastic light scattering (Raman scattering) is used to infer the relative concentration of two different isotopes of carbon-dioxide. Gas velocity measurements have many applications in engineering. We are attempting to develop a non-intrusive measurement technique that does not rely on flow seeding, which can be difficult to achieve in gas flows, but relies on scattering from the gas molecules themselves. The isotope ratio measurement work was stimulated by a medical application - detection and treatment of ulcers. In addition to other medical applications, there are also environmental monitoring applications of the technique.