We present experimental and theoretical results of photorefractive one-dimensional self-focusing in an Fe-doped KNbO<sub>3</sub> crystal. The self-focusing is investigated by Z-scan experiments with and without an applied electric field. We observe the strongest focusing effect for a ratio I⁁/I<sub>D</sub>≈6 of the beam peak intensity to the so-called dark intensity (the intensity at which photoconductivity is equal to the conductivity in the dark). The good agreement between the presented theory and experiment in the Z-scan technique allows the precise determination of dark intensity, the photovoltaic field, and the electric field inside the crystal.
© 1998 Optical Society of America
Roland Ryf, Andreas Lötscher, Christian Bosshard, Marko Zgonik, and Peter Günter, "Z-scan-based investigations of photorefractive self-focusing in KNbO3 crystals," J. Opt. Soc. Am. B 15, 989-995 (1998)