Copper-ion point defects in the photorefractive material (KxNa1-x)0.4(SryBa1-y)0.8Nb2O6.

Abstract

We show that Cu ions doped in (${\mathrm{K}}_{\mathit{x}}$${\mathrm{Na}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${)}_{0.4}$(${\mathrm{Sr}}_{\mathit{y}}$${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${)}_{0.8}$${\mathrm{Nb}}_{2}$${\mathrm{O}}_{6}$ (KNSBN) form two energy levels in the band gap, which increase the effective charge-combination-center concentration ${\mathit{N}}_{\mathrm{eff}}$. The two-wave coupling gain and the response speed of KNSBN crystals are increased while the photoconductivity and the effects of a dc field on the photorefractive properties are reduced. Self-pumped phase conjugation (SPPC) experiments have revealed that the effects of Cu ions on the photorefractive properties have a wavelength dependence. The SPPC response time at the ${\mathit{e}}^{\mathrm{\ensuremath{-}}1}$ level can be shortened to 200 ms.