Near-infrared second-harmonic generation versus mid-infrared optical parametric oscillation in multigrating and fan-out PPMgO: LN structures pumped by a repetitively pulsed 2-μm Tm³⁺:Lu₂O₃-ceramics laser

Mid-infrared optical parametric oscillators based on multigrating and fan-out periodically poled MgO-doped LiNbO₃ (PPMgO:LN) crystals pumped with a repetitively pulsed Tm³:Lu₂O₃-ceramics laser at 1966 nm were experimentally studied. The 983-nm wavelength second-harmonic generation of the pumping beam was found to be competing with the parametric oscillations in PPMgO:LN crystals. Double-resonant optical parametric oscillations near the degeneracy point at 3.93 μm were observed in multigrating PPMgO:LN crystal, but were not detected in the fan-out PPMgO:LN structure due to pump-power depletion by second-harmonic generation. Efficient second-harmonic generation with an average power up to 4.66 W at 983 nm was achieved in the fan-out PPMgO:LN crystal.