Quasi‐phase‐matched second‐harmonic generation of blue light in periodically poled LiNbO3

LiNbO3 crystals with periodically alternating ferroelectric domains have been produced using laser‐heated pedestal growth. Domain thicknesses as small as 1 μm have been achieved. This material was applied to room‐temperature, quasi‐phase‐matched frequency doubling to generate light at wavelengths as short as 407 nm, using the d33 and d22 nonlinear coefficients. The measured conversion efficiencies and wavelength and temperature tuning bandwidths are consistent with an effective interaction length of ≊320 μm (>230 domains). An initial test with high‐intensity focused blue beams showed that the periodically poled material exhibits no discernible photorefractive damage effect.