Optimization of Blue Photorefractive Properties and Exponential Gain of Photorefraction in Sc-Doped Ru:Fe:LiNbO3 Crystals

Abstract

Sc:Ru:Fe:LiNbO3 crystals were grown from congruent melt by using the Czochralski method. A series of LiNbO3 crystals (Li/Nb = 48.6/51.4) with 0.1 wt% RuO2, 0.06 wt% Fe2O3 and various concentrations of Sc203 were prepared. RF1 and RF4 refers to the samples containing 0 mol% Sc203 and 3 mol% Sc203, respectively. The photorefractive properties of RF4 were measured by Kr+ laser (λ = 476 nm blue light): ηs = 75.7%, τw = 11 s, M/# = 19.52, S = 2.85 cmJ−1, Γ = 31.8 cm−1 and ∆nmax = 6.66 × 10−5. The photorefractive properties of five systems (ηs, M/#, S, Γ and ∆nmax) under 476 nm wavelength from RF1 to RF4 continually increased the response time, while τw was continually shortened. Comparing the photorefractive properties of Sc (1 mol%):Ru (0.1 wt%):Fe (0.06 wt%): LiNbO3 measured by Kr+ laser (λ = 476 nm blue light) with Sc (1 mol%):Fe (0.06 wt%):LiNbO3 measured by He-Ne laser (633 nm red light), ηs increased by a factor of 1.9, Vw (response rate) increased by a factor of 13.9, M/# increased by a factor of 1.8 and S increased by a factor of 32. The ∆nmax improved by a factor of 1.4. A strong blue photorefraction was created by the two-center effect and the remarkable characteristic of being in phase between the two gratings recorded in shallow and deep trap centers. The photorefractive properties (ηS, τw, M/#, S, ∆nmax) were increased with an increase in Sc3+ ion concentration. Damage-resistant dopants such as Sc3+ ions were no longer resistant to damage, but they enhanced the photorefractive properties at the 476 nm wavelength. The experimental results clearly show that Sc-doped two-center Ru:Fe:LiNbO3 crystal is a promising candidate blue photorefraction material for volume holographic storage. Sc-doped LiNbO3 crystal can significantly enhance the blue photorefractive properties according to the experimental parameters. Therefore, the Sc:Ru:Fe:LiNbO3 crystal has better photorefractive properties than the Ru:Fe:LiNbO3 crystal.