Type II phase matching in a β-barium borate optical parametric oscillator

We report the first demonstration of a type II phase-matched optical parametric oscillator using β-barium borate (BBO) as the nonlinear optical material. The optical parametric oscillator (OPO) is pumped at 354.7 nm and tuning has been demonstrated over 0.48–0.63 μm and 0.81–1.36 μm. The linewidth of the device, without line narrowing elements, is 0.5–3.0 Å, which is dramatically narrower than that of a corresponding type I phase-matched BBO OPO. Experimentally usable conversion efficiencies of 12% have been achieved.