Direct studies on nonlinear oxide crystals able to generate mid-infrared parametric light (Conference Presentation)

Nowadays, there is a real need in all solid-state sources emitting a high energy and tunable coherent light covering Band II of transparency of the atmosphere (2-5 µm). The best alternative is frequency down-conversion in a nonlinear crystal of a monochromatic wavelength emitted by a commercial laser. The requested performances of the crystal are a high damage threshold and phase-matching conditions associated with large conversion efficiencies. It is the case of the oxyde crystals KTiOPO4 (KTP) and the periodically poled LiNbO3 (PPLN) that are mainly used. The goal of this talk is to give an overview of their full characterization by using the sphere method we developed many years ago. We will also report recent data of new promising oxyde crystals as La3Ga5.5Ta0.5O14 (LGT), NaI3O8 and periodically poled KTiOPO4 (PPKTP). All our data can be used per se. They also lead to the main parameters enabling calculations of the best use of oxyde crystals in optical parametric generators (OPG).