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Updated: Aug 17, 2026

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Widely tunable continuous-wave mid-infrared radiation (5.5-11 microm) by difference-frequency generation in LiInS2
Weidong Chen1, Emmanuelle Poullet, Jean Burie
1Laboratoire de Physicochimie de l'Atmosphere (Unité Mixte de Recherche, Centre National de la Recherche Scientifique 8101), Université du Littoral Côte d'Opale, 189A, Avenue Maurice Schuman, 59140 Dunkerque, France. chen@univ-littoral.fr
Abstract:
The first demonstration, to the best of our knowledge, of continuous-wave (cw) difference-frequency generation (DFG) in LiInS2 crystal is reported. Wide spectral coverage (5.5-11.3 microm) has been obtained with angle and wavelength tuning for type II (eoe) critically phase-matched parametric interaction. The phase-matching conditions in cw DFG have been investigated, which allowed us to improve the Sellmeier parameters by use of a two-pole dispersion equation. An effective nonlinear coefficient deff = 6.9 +/- 0.8 pm/V has been determined at approximately 7 microm relative to the well-known nonlinear coefficient d36 of AgGaS2, which yields a power-conversion efficiency of approximately 12.4 microW/(W2 cm). We evaluated the high-resolution spectral characteristics of the DFG source by recording C2H2 and SO2 spectra.
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