Improved CdGeAs2 crystal produces tunable mid-IR radiation at room temperature

Improved CdGeAs2 crystal produces tunable mid-IR radiation at room temperature

Researchers Konstantin L. Vodopyanov of Blackett Laboratory (London, England) and Peter G. Schunemann of Sanders (Nashua, NH) obtained efficient room-temperature generation of pulsed mid-infrared radiation in a cadmium germanium arsenide (CdGeAs2) crystal using difference-frequency generation (DFG) between signal and idler waves of an erbium-laser-pumped zinc germanium phosphide (ZnGeP2) optical parametric generator. The output was continuously tunable between 6.8 and 20.1 µm. An improved CdGeAs2 crystal allowed the room-temperature frequency generation and was grown at Sanders by the horizontal gradient freeze technique. The maximum DFG conversion efficiency was 20% between 10 and 13 µm and exceeded 10% from 7 to 16 µm--corresponding to a few kilowatts of peak power. The 20% external conversion efficiency is equivalent to 39% internal conversion efficiency. Tunable sources emitting in this wavelength region are of interest for a variety of applications including spectroscopy, remote sensing, biology, and medicine.