Tunable mid-infrared (6.3-12 μm)optical vortex pulse generation.

We demonstrated widely tunable mid-infrared (6.3-12 μm) optical vortex pulse generation from a ZGP difference frequency generator pumped by a 2 μm optical vortex laser with a cascaded KTP geometry. The mid-infrared vortex output carried the same topological charge as that of the 1 μm pump output without any destruction. A pulse energy of >135 μJ was obtained in the wavelength region of 6.3-7.0 μm.