Enhanced Gas Detection

About

Background: The detection and characterization of molecular gases in a given sample is a relatively difficult challenge. Usually, this task is relegated to expensive and time consuming processes like mass spectrometry and gas chromatography. Furthermore, numerous industrial applications require such gas-phase analysis for pollution and process control. In particular, the operation of large natural gas-fired turbine generators requires real-time analysis of constituent hydrocarbon concentration in order to provide energy content information about the gaseous fuel, and subsequently, inputs for controlling fuel/air ratio and burner temperature.    Technology: Investigators have developed a novel technique for studying gaseous samples which uses a new collection method for Raman spectroscopy. In this technique, gasses are introduced inside the light-guiding core of a hollow waveguide. Either lengths of hollow-core photonic-bandgap fiber or internally reflective capillary waveguides are used to both contain sample gases and collect Raman photons. The optical confinement characteristics of these types of hollow-waveguides allow a high power-density laser beam to propagate a long distance along with the low-volume gaseous sample. The Raman signal strength (power) collected using our gas cells can be hundreds of times larger than that which can be obtained in free-space. Along with this improvement in collected Raman power comes shorter minimum interrogation times and higher sensitivities to trace gasses. In general, the technique paves the way for the construction of a gas Raman spectrometer with low-cost components and high-accuracy.