Mitigation of transverse domain growth in two-dimensional polarization switching of lithium niobate

This letter reports a charge control mechanism to mitigate the growth of transverse domain in the two-dimensional periodical polarization switching of Z-cut congruent-grown lithium niobate. This mechanism is established in a two-step procedure consisting of a first high temperature treatment followed by pulsed field poling. The ferroelectric χ(2) nonlinear photonic crystal thus formed exhibits a domain size as small as 3.3 μm and can emit an array of second harmonic green lasers when pumped by a Nd:yttritium–aluminum–garnet laser. These observations are ascribed to the (i) selective 180° domain nucleation underneath the oxidized electrode, and (ii) confinement of transverse domain motion to the positively charged boundary formed by the heat treatment.