Mid-infrared Continuous-wave Optical Parametric Oscillator with a Fan-out Grating MgO:PPLN Operating Up to 5.3 μm

We report on a continuous-wave (cw) optical parametric oscillator (OPO) optimized for mid-infrared emission above 5.0 mu m. The OPO is based on a magnesium-oxide-doped periodically poled LiNbO3 (MgO:PPLN) crystal with a fan-out grating design. A linear two-mirror cavity resonating both at the pump and signal wavelengths is stabilized to the pump laser by using the modified Pound-Drever-Hall (PDH) method. The idler wavelength is continuously tunable from 4.7 mu m up to 5.3 mu m by varying the poling period of the fan-out grating crystal. Pumped by a diode-pumped solid state (DPSS) laser with a power of 1.1 W at 1064 nm, the maximum idler output power is measured to be 5.3 mW at 4.8 mu m. The output power above 5.0 mu m is reduced to the hundreds of mu W level due to increased absorption in the crystal, but is stable and strong enough to be measured with a conventional detector.