Abstract

Mid-infrared tunable sources are becoming of considerable interest for applications in environment monitoring. Optical parametric generation is a good candidate for the production of mid-infrared wavelengths from near ir sources. However, apart from a dew peculiar chalcopyrite materials (ZnGeP₂, AgGaSe₂,…), most of the usual nonlinear crystal absorb strongly above 5 μm. On the opposite, semiconductors of the main technological stream (GaAs, InP, ZnSe,..) are excellent candidate for optical frequency conversion because of 1) high χ⁽²⁾, 2) high threshold damage power, 3) excellent transparency over the 1-15 μm range, 4) good mechanical properties, 5) possibility of future integration with the pumping source. However, most of these materials are isotropic so that no birefringence phase-matching scenarios are available. Recently, several new phase matching techniques have been investigated: artificial birefringence in GaAs/AlOx waveguides and alternate stack quasi-phase matching . In these experiments, no results of tunability in the 8-12 μm range has been obtained for several reasons (absorption of AlOx, stack thickness resonance,…). In this Conference, we present what we believe to be the first largely tunable (8-12 μm) difference frequency generation (DFG) emission in GaAs and ZnSe plates. We have made use of the low optical dispersions displayed by these materials in the mid-infrared to obtain large coherence length and thus high conversion efficiency on a single coherence length.

© 2001 EPS