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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 (M 2 ) of the mid-infrared idler output was measured to be <1.75.

We investigated high energy, near and mid-infrared optical vortex lasers formed by a 1 μm optical vortex-pumped KTiOAsO4 (KTA) optical parametric oscillator. The orbital angular momentum (OAM) of the pump beam can be selectively transferred to the signal or idler output by changing the reflectivity of the output coupler. With this system, 1.535 µm vortex signal output with an energy of 2.04 mJ and 3.468 µm vortex idler output with an energy of 1.75 mJ were obtained with a maximum pump energy of 21 mJ, corresponding to slope efficiencies of 14% and 10%, respectively. The spectral bandwidth (full width at half maximum, FWHM) of the signal and idler vortex outputs were measured to be Δλs ~ 1.3 nm (~ 5.5 cm−1) and Δλi ~ 1.7 nm (~ 1.4 cm−1), respectively.

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