Charge transport properties of undoped congruent lithium niobate crystals

Time-resolved light-induced birefringence measurements based on a phase compensation technique are used to determine the charge transport properties of congruent, nominally-undoped lithium niobate crystals (LiNbO3). Some of the crystals are conventionally oxidized. The steady-state space-charge field Epv, the bulk photovoltaic coefficient β, and the photoconductivity σph are determined in the intensity range (30–30 000) W/cm2. The photovoltaic coefficient β increases by one order of magnitude over this intensity range, the space-charge field Epv even by two orders of magnitude. We discuss the results in the context of the known one- and two-center charge transport models for LiNbO3. The experimental findings presented here are of relevance for the long-standing problem of optical damage in such crystals, which inhibits their use in high-intensity applications like nonlinear optics.