Picojoule threshold, picosecond optical parametric generation in reverse proton-exchanged lithium niobate waveguides

We have demonstrated picosecond optical parametric generation in reverse proton-exchanged waveguides in periodically poled lithium niobate with thresholds as low as 200 pJ. Near-transform-limited near-infrared pulses were obtained from cascaded optical parametric generation. For a 1.8-ps (FWHM) pump pulse at 769.6 nm, a saturated internal photon-conversion efficiency of 33% was obtained with 1 nJ of pump energy. The signal-wavelength tuning range was from 1.15 μm to 2.3 μm with a pump wavelength between 770 nm and 789.5 nm. Numerical simulations well predicted the mechanism for the transform-limited pulse generation. These results enable optical parametric generation devices with low threshold and good temporal properties with a simple single-pass setup.