High-efficiency frequency converters with periodically-poled Rb-doped KTiOPO4

Periodic structuring of ferroelectric domains in 2 mol% Rb-doped KTP is demonstrated using a room-temperature electric-field poling. Drastically reduced ionic conductivity in this material, or 2-orders of magnitude lower than in flux-grown KTP, makes it a good candidate for fabrication of quasi-phase-matched frequency converters. A coercive field of 3.4 kV/mm has been measured at room temperature. The dispersion of the index of refraction and effective nonlinearity in quasi-phase-matched structures in Rb-doped KTP did not show significant difference from KTP. A normalized conversion efficiency of 2.5% W−1 cm−1 for the frequency-doubling of 908.4 nm has been obtained. A singly-resonant mid-infrared optical parametric oscillator with periodically-poled Rb-doped KTP generating 1.53 μm signal and 3.49 μm idler had threshold of 51 MW/cm2 which is comparable to the best-quality periodically-poled KTP structures in the same optical cavity.