Mid-infrared optical parametric oscillator based on ZnGeP2 pumpe...

We present a 3~5 \mum optical parametric oscillator (OPO) based on ZGP pumped by KTP OPO 2.1-\mum laser. The tuning curves of ZGP OPO are calculated. The 8 \times 6 \times 18 (mm) ZGP crystal, whose end faces are antireflection coated at 2.1 and 3.7~4.6 \mum, is cut as \theta =53.5o, \phi =0o. When the pump power of 2.1-\mu m polarized laser is 15 W at 8 kHz, 5.7-W output power and 46.6% slope efficiency are obtained with a ZGPtype I phase match. Central wavelengths of the signal and idler laser