Article

Applied Physics B

, 89:123

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

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

  • A.K.Y. NgaiAffiliated withLife Science Trace Gas Facility, Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University
  • , S.T. PersijnAffiliated withLife Science Trace Gas Facility, Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University
  • , I.D. LindsayAffiliated withLaser Physics and Nonlinear Optics Group, Faculty of Science and Technology, University of Twente
  • , A.A. KosterevAffiliated withDepartment of Electrical and Computer Engineering, Rice University
  • , P. GroßAffiliated withLaser Physics and Nonlinear Optics Group, Faculty of Science and Technology, University of Twente
  • , C.J. LeeAffiliated withLaser Physics and Nonlinear Optics Group, Faculty of Science and Technology, University of Twente
  • , S.M. CristescuAffiliated withLife Science Trace Gas Facility, Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University
  • , F.K. TittelAffiliated withDepartment of Electrical and Computer Engineering, Rice University
  • , K.-J. BollerAffiliated withLaser Physics and Nonlinear Optics Group, Faculty of Science and Technology, University of Twente
    • , F.J.M. HarrenAffiliated withLife Science Trace Gas Facility, Molecular and Laser Physics, Institute for Molecules and Materials, Radboud University Email author 

Abstract

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.

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.