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

Small-Size Resonant Photoacoustic Cell of Inclined Geometry for Gas Detection

A photoacoustic cell intended for laser detection of trace gases is represented. The cell is adapted so as to enhance the gas-detection performance and, simultaneously, to reduce the cell size. The cell design provides an efficient cancellation of the window background (a parasite response due to absorption of laser beam in the cell windows) and acoustic isolation from the environment for an acoustic resonance of the cell. The useful photoacoustic response from a detected gas, window background and noise are analyzed in demonstration experiments as functions of the modulation frequency for a prototype cell with the internal volume ~ 0.5 cm^3. The minimal detectable absorption for the prototype is estimated to be ~ 1.2 10^{-8} cm^{-1} W Hz^{-1/2}.Comment: 11 pages, 5 figure

Spectroscopic applications of continuous wave optical parametric oscillators

Contains fulltext : 72578.pdf (publisher's version ) (Open Access)RU, Molecular and Laser Physics, 3 juni 2008Promotor : Parker, D.H.127 p

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

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

Combined wide pump tuning and high power of a continuous-wave, singly resonant optical parametric oscillator

Contains fulltext : 60225pub.pdf (publisher's version ) (Closed access)A new singly resonant, single-frequency optical parametric oscillator (OPO) has been developed for the 2.6-4.7 mum infrared wavelength region, using a high power (>20 W), widely tunable (1024-1034 nm) Yb:YAG pump source. With the OPO frequency stabilized with an intracavity etalon, the OPO achieved an idler output power of 3 W at 2.954 mum. Tuning of the idler frequency was achieved by longitudinal mode-hop tuning of the pump source (FSR 100 MHz). In this way an idler frequency scan of 100-150 GHz could be obtained, after which the signal frequency hops ahead over the FSR of the intracavity etalon of the OPO (207 GHz). Due to un-optimized mirror coatings for the OPO cavity and PPLN crystal, the frequency stability was limited to 90 MHz over 1 s, with an unaffected long-term frequency stability of 250 MHz over 200 seconds

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

Optical parametric oscillator-based photoacoustic detection of CO 2 at 4.23 µm allows real-time monitoring of the respiration of small insects

A continuous wave, single frequency and continuously tunable optical parametric oscillator is used in combination with photoacoustic spectroscopy to detect trace emissions of CO2 from insects under atmospheric conditions. The optical parametric oscillator (OPO) contains a periodically poled lithium niobate crystal and is tunable over the 3.9 to 4.8 ¿m infrared wavelength region. With the strong rotational-vibrational absorption band of CO2 at 4.23 ¿m, it is possible to detect CO2 down to 7 parts per billion volume using 20 mW of the OPO beam. This detection sensitivity was achieved by adding 4% of SF6 gas to the atmospheric gas mixture to overcome the slow vibrational relaxation of the excited CO2 levels. The usefulness of this system is demonstrated by real-time measuring of the fluctuations of the CO2 concentration in the breath of a single ant (Lasius niger) and individual fruit flies (Drosophila melanogaster)