β-Barium borate and lithium triborate picosecond parametric oscillators pumped by a frequency-tripled passive negative-feedback mode-locked Nd:YAG laser

We report on an investigation of a singly resonant picosecond optical parametric oscillator in a noncollinear configuration for which we alternatively used β-barium borate and lithium triborate in a type-I phase-matching configuration tunable from 407 to 2780 nm and from 452 and 1650 nm, respectively. The parametric oscillator was synchronously pumped by the third harmonic of a passive negative-feedback actively–passively mode-locked Nd:YAG laser–amplifier system, and long and flat trains of short bandwidth-limited 9-ps pulses were produced. We obtained conversion efficiency into the idler wave (at 900 nm) of as high as 10% and overall efficiency as high as 26%. We present a numerical model of the operation that agrees very well with the experimental results. The simplicity and ruggedness are the main strengths of this source when high-power conversion capability and wide tunability are the main requirements.