High-power, continuous-wave, tunable mid-IR, higher-order vortex beam optical parametric oscillator.

We report on a novel experimental scheme to generate continuous-wave (cw), high-power, and higher-order optical vortices tunable across a mid-IR wavelength range. Using a cw, two-crystal, singly resonant optical parametric oscillator (T-SRO) and pumping one of the crystals with a Gaussian beam and the other crystal with optical vortices of orders l=1-6, we have directly transferred the vortices at near-IR to the mid-IR wavelength range. The idler vortices of orders l=1-6 are tunable across 2276-3576 nm with a maximum output power of 6.8 W at an order of l=1 for the pump power of 25 W, corresponding to a near-IR vortex to mid-IR vortex conversion efficiency as high as 27.2%. Unlike the SROs generating optical vortices restricted to lower orders (≤2) due to the elevated operation threshold of SROs with higher-order pump vortices, here the coherent energy coupling between the resonant signals of two crystals of T-SRO facilitates the transfer of pump vortex of any order to the idler wavelength without a stringent operation threshold condition. The generic experimental scheme can be used in any wavelength range across the electromagnetic spectrum and in all timescales, from cw to ultrafast regimes.