ZnGeP2 optical parametric oscillator with 3.8-12.4-μm tunability

A ZnGeP2 (ZGP) optical parametric oscillator (OPO) with wide mid-IR tunability has been demonstrated. The singly resonant angle-tuned ZGP OPO was pumped by 100-ns erbium laser pulses at lambda = 2.93 mu m and yielded output that was continuously tunable from 3.8 to 12.4 mu m (type I phase matching) and from 4 to 10 mu m (type II phase matching). An OPO pump threshold was less than 1 mJ in the whole 4-12 mu m range of the output, and the quantum conversion efficiency reached 35%. An OPO linewidth was typically a few wave numbers; however, with a single intracavity etalon (uncoated Si plate) in a type II OPO it was narrowed to <0.5 cm(-1) We demonstrate the sensitive detection of N2O gas with the narrow-linewidth OPO. (C) 2000 Otical Society of America.