Optical second harmonic generation in ferro- and para-electric phases of PbHPO4

Publisher Website
Google Scholar
Abstract
Optical second harmonic generation was measured across the ferroelectric phase transition in PbHPO4 under an applied electric field. The authors show that linear coupling of nonlinear susceptibility to the order parameter describes well the temperature and electric field dependence of d111. This indicates simultaneous reorientation of heavy ions and ordering of protons, contrary to recent Raman and neutron scattering results. Some residual SHG generation can be obtained in the para-electric phase with no applied electric field in newly polished and mounted samples. This SHG signal is attributed to the perturbation of the crystal by defects, which can be annealed nearly completely with a pulsed electric field. P2/c macroscopic symmetry is deduced for the para-electric phase.