Near and mid-infrared optical vortex parametric oscillator based on KTA

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 Δλ_s ~ 1.3 nm (~ 5.5 cm^-1) and Δλ_i ~ 1.7 nm (~ 1.4 cm^-1), respectively.