Highly efficient millijoule-level 3.5 µm MgO-doped periodically poled lithium niobate optical parametric oscillator

Abstract

We report a millijoule-level mid-infrared MgO-doped periodically poled lithium niobate (MgO:PPLN) optical parametric oscillator pumped by a 1.064 µm nanosecond laser. The maximum mid-infrared 3.5 µm idler output energy reached 3.65 mJ at the pump energy of 21 mJ, corresponding to a photon conversion efficiency of 57%. The wavelength tunabilities of the signal and idler outputs were also realized, with the continuous tuning ranges of 1.501 to 1.558 µm and 3.650 to 3.353 µm, respectively, by controlling the temperature of the MgO:PPLN crystal. The beam quality factor (M2) of the mid-infrared idler output was measured to be <1.75.