Scanning picosecond optical parametric source using potassium dihydrogen phosphate in the visible and near infrared

An optical parametric source using angle-tuned type II potassium dihydrogen phosphate (KDP) as the nonlinear medium and pumped with 35-ps, 355-nm pulses from an active–passive mode-locked Nd:YAG laser, is described. With a 1.35-mJ pump pulse, conversion efficiencies ranging from 1%–40% in the spectral range 450–650 and 800–1600 nm have been achieved. The ΔνΔt products can approach the transform limit, although 15–30 times transform limited is more typical. The merits of the combination of pump wavelength and phase match used here are discussed with respect to the tuning range, spectral width, and ease of operation. Automated scanning was achieved by placing the crystals on stepper-motor controlled rotation stages. A convenient, easily reproducible high peak power source rapidly tunable over much of the visible and near infrared is obtained.