Continuous wave optical parametric oscillator for quartz-enhanced photoacoustic trace gas sensing

A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3–4 μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO output over 5.2 cm-1 and continuous spectral coverage exceeding 16.5 cm-1 were achieved via electronic pump source tuning alone. Online monitoring of the idler wavelength, with feedback to the DBR diode laser, provided an automated closed-loop control allowing arbitrary idler wavelength selection within the pump tuning range and locking of the idler wavelength with a stability of 1.7×10-3 cm-1 over at least 30 min.\ud \ud Using this approach, we locked the idler wavelength at an ethane absorption peak and obtained QEPAS data to verify the linear response of the QEPAS signal at different ethane concentrations (100 ppbv-20 ppmv) and different power levels. The detection limit for ethane was determined to be 13 ppbv (20 s averaging), corresponding to a normalized noise equivalent absorption coefficient of 4.4×10-7 cm-1  W/Hz1/2

Selective trace gas detection of complex molecules with a continuous wave optical parametric oscillator using a planar jet expansion

Contains fulltext : 36451.pdf (publisher's version ) (Open Access)The authors present a trace gas detection method for complex molecules using continuous cavity ring-down spectroscopy in combination with a continuous wave optical parametric oscillator (tunability wavelength: 2.8-4.8 mu m; power: 1 W) sampling a supersonic planar jet expansion (nozzle dimension: 3 cmx80 mu m). The improved molecular selectivity allows simultaneous detection of larger numbers of complex molecules. With a total optical path length of 180 m in the planar jet, a detection limit for methanol in an air expansion was determined at 70 ppbv, corresponding to a minimal detectable absorption of 2.2x10(-8) cm(-1) (over 90 s). (c) 2007 American Institute of Physics

Singly resonant cw OPO with simple wavelength tuning

Contains fulltext : 72618pub.pdf (publisher's version ) (Open Access)21 p

A versatile photoacoustic spectrometer for sensitive trace-gas analysis in the mid-infrared wavelength region (5.1-8.0 and 2.8-4.1 mu m)

Contains fulltext : 100908.pdf (publisher's version ) (Closed access

Study of gas exchange in insects by sensitive laser photoacoustic spectroscopy

Contains fulltext : 35374pub.pdf (publisher's version ) (Closed access)Although quantifying gas exchange in small insect species is of great biological interest, the progress in this field of research is hampered by the inability of most gas detectors to monitor the low emission rates from these insects. Recently, laser based photoacoustic spectroscopy (LPAS) has emerged as a highly sensitive technique that allows gases to be detected at sub-ppb level. In this work, LPAS was used to study gas exchange in two different insect species. Firstly, loss of water by the minute Western Flower thrips (Frankliniella occidentalis , average weight 50 mu g) was recorded by means of CO-laser PAS. Water loss by a single thrips could be on-line recorded with a practical detection limit of 30 ppb. Insects released H2O in rather regular patterns, possibly due to discontinuous respiration. These data represent on-line H2O loss recordings of the smallest insects measured hitherto. In a second experiment, the inert tracer gas SF6 was used to determine the tracheal volume of Attacus atlas pupae. Insects were loaded with SF6 and subsequent release of this gas was monitored using CO2-laser PAS. Based on the amount of released SF6 , one has determined the tracheal volume of Attacus atlas pupae. The value obtained (170 +/- 53 mu L/g) is in good correspondence with data obtained by other techniques. In addition, with this technique, respiration patterns can be recorded; the results show a good correspondence with the simultaneous recordings of CO2 release using a commercial CO2 analyser

Selective trace gas detection of complex molecules with a continuous wave optical parametric oscillator using a planar jet expansion

The authors present a trace gas detection method for complex molecules using continuous cavity ring-down spectroscopy in combination with a continuous wave optical parametric oscillator (tunability wavelength: 2.8-4.8 mu m; power: 1 W) sampling a supersonic planar jet expansion (nozzle dimension: 3 cmx80 mu m). The improved molecular selectivity allows simultaneous detection of larger numbers of complex molecules. With a total optical path length of 180 m in the planar jet, a detection limit for methanol in an air expansion was determined at 70 ppbv, corresponding to a minimal detectable absorption of 2.2x10(-8) cm(-1) (over 90 s). (c) 2007 American Institute of Physics

CO laser absorption coefficients for gases of biological relevance: H2O, CO2, ethanol, acetaldehyde, and ethylene

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Photoacoustic Spectroscopy using continuous wave Optical Parametric Oscillators

Contains fulltext : 36313pub.pdf (publisher's version ) (Closed access)511 p

Photoacoustic spectroscopy using continuouys wave optical parametric oscillators

Contains fulltext : 71923.pdf (publisher's version ) (Closed access