High–Efficiency, Widely Tunable MgO: PPLN Optical Parametric Oscillator

We report on the investigation of a high–efficiency, widely tunable femtosecond optical parametric oscillator (OPO) based on a multi–period MgO–doped periodically poled lithium niobite (MgO: PPLN) crystal, pumped by an all–solid–state femtosecond mode–locked Yb: KGW laser at 1030 nm providing 100 fs pulses. With 6 W pump power, the OPO generates 2.68 W of signal power at 1540 nm and 1.2 W of idler power at 3110 nm, which corresponds to the total conversion efficiency adding up to 67.4%. To the best of our knowledge, this is the highest conversion efficiency of a femtosecond OPO. Meanwhile, in order to obtain a broad optical spectrum range, both the grating period and working temperature are tuned, resulting in tunable signals of 1.43–1.78 µm and idlers of 2.44–3.68 µm. This source will be used to generate a femtosecond mid–infrared laser of wavelength range 3.7–6.5 µm and tens milliwatts average power through difference frequency generation (DFG).