15min:

ROBERTO GRILLI, School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K.; LUCA CIAFFONI, GRANT A. D. RITCHIE, Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, U.K.; AND ANDREW J. ORR-EWING, School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K..

A periodically poled LiNbO₃ waveguide has been used to produce up to 200 µW of mid-infrared light around 3081 cm^-1 with a wide tunability range of >33 cm^-1. Two commercial near-infrared diode lasers at 1.064 µm (pump) and 1.583 µm (signal) are mixed in a nonlinear optical crystal to achieve difference frequency generation. The 48 mm long direct-bonded quasi-phase matched periodically poled LiNbO₃ waveguide shows a conversion efficiency of 12.3 %/W. The radiation sits in an important window of the mid-infrared spectral region, where a large number of fundamental vibrations of several hydrocarbons occur. Applications in trace gas detection have been demonstrated for ethene, using multi-pass absorption coupled with wavelength modulation spectroscopy to reach a minimum absorption coefficient of 3 × 10^-7 cm^-1 Hz^-1/2. The relatively high power of the mid-infrared idler radiation obtained shows great potential for higher sensitive techniques such as cavity enhanced absorption spectroscopy and cavity ring-down spectroscopy, and preliminary results will be presented.