Second-harmonic generation and origin of polar configuration inKTaO3:Li

Abstract

Results are presented for the second-harmonic generation of light in ${\mathrm{K}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Li}}_{\mathit{x}}$ ${\mathrm{TaO}}_3$ for x=1.6%, 2.6%, 3.4%, and 6%. From the second-harmonic efficiency and from birefringence results, it is concluded that below the freezing temperature ${\mathit{T}}_{\mathit{f}}$, ${\mathrm{KTaO}}_3$:Li polar displacements are correlated over distances ${\xi }_{\mathit{d}}$, which increase continuously with dopant concentration x from 6 nm at x=1.6% to 23 nm at x=6%. Below ${\mathit{T}}_{\mathit{f}}$, ${\xi }_{\mathit{d}}$ is nearly independent of T. Quadrupolar distortions are correlated over much larger distances, comparable to the wavelength of light.