Green and ultraviolet quasi-phase-matched second harmonic generation in bulk periodically-poled KTiOPO₄

A periodically-poled flux-grown KTP crystal was used for first order quasi-phase-matched (QPM) second harmonic generation of a Nd:YAG laser. The normalized conversion efficiency of the 1 cm long, 0.5 mm thick sample was 1.28% W^-1. A lower limit on the nonlinear coefficient of KTP, d₃₃ ≥ 14.9 ± 1.5 pm/V was derived from these measurements. The temperature and wavelength tuning coefficients near 1064 nm were determined. The same device was also used for third order QPM frequency doubling of 784 nm light, and the normalized conversion efficiency in this case was 0.12% W^-1.