Spontaneous Raman scattering at trace gas concentrations with a pressurized external multipass cavity
Juan Gomez Velez, Andreas Müller
Abstract
Abstract A setup is described with which the spontaneous Raman scattering rate from pressurized gas samples is greatly enhanced inside a near-concentric optical cavity. The pump source is a high power multimode semiconductor laser diode that receives optical feedback from the cavity by way of a volume Bragg grating, resulting in a linewidth of 80 pm and circulating power close to 100 W. Under pressurization (up to 8 bar) a limit of detection below 100 parts-per-billion was obtained for gaseous hydrogen, measured in ambient air and in breath. Furthermore, isotopic trace detection is demonstrated by headspace measurements of semiheavy water.
Topics & Concepts
Materials scienceRaman scatteringLaser linewidthOpticsTrace gasBar (unit)LaserParts-per notationVolume (thermodynamics)Detection limitOptical powerOptoelectronicsRaman spectroscopyChemistryPhysicsMeteorologyChromatographyQuantum mechanicsOrganic chemistrySpectroscopy and Laser ApplicationsAdvanced Chemical Sensor TechnologiesSpectroscopy Techniques in Biomedical and Chemical Research