Periodically poled KTiOP/sub 4/ for low-threshold parametric oscillation in the spectral region around 2 /spl mu/m

Summary form only. Ferroelectric domain inversion in optical materials with high nonlinearity allows design and fabrication of quasi-phase-matched (QPM) structures where the noncritical parametric interaction over the whole tuning band can be achieved utilising the highest nonlinear coefficient in these materials. PPKTP has an effective nonlinear coefficient of about 8-10 pm/V, it can be operated at room temperature, requires less stringent temperature stabilisation and is less susceptible to the photorefractive effect as compared to LiNbO/sub 3/. The QPM structures in PPKTP with thickness of up to 3 mm have been primarily used to generated mJ-level parametric pulses. In this work we demonstrate that nonlinearity in PPKTP is large enough to realise OPO thresholds around 10 /spl mu/J in 10 mm to 20 mm long QPM structures when pumped at 1064 nm wavelength from a LD-pumped Nd:YAG laser.