Mid-infrared idler-resonant optical vortex parametric oscillator based on MgO:PPLN

We present a high beam quality, mid-infrared, wavelength tunable, idler-resonant optical vortex parametric oscillator based on a single-grating MgO-doped periodically poled lithium niobate (MgO:PPLN) crystal. The compact, plane-concave cavity used in this work enabled transfer of the orbital angular momentum (OAM) of the pump field to the idler field, to deliver high beam quality, mid-infrared vortex beam emission with measured M2 factors of 2.2 in both orthogonal directions. The wavelengths of the signal (which had a TEM00/Gaussian-like spatial profile) and the idler vortex outputs could be tuned across the ranges 1.505–1.566 µm and 3.318–3.628 µm, respectively, by changing the MgO:PPLN crystal temperature in the range 25 to 200℃. We also investigate the mechanism of OAM transfer within the idler-resonant MgO:PPLN optical parametric oscillator (OPO) by tuning the cavity length. Here, we find that the OAM of the pump beam can be selectively transferred to the signal field by simply extending the cavity length. The maximum measured signal and idler vortex output energies were 3.3 mJ and 1.1 mJ, respectively, and were achieved using both compact and extended cavities at a pump energy of 21 mJ.