Photorefractive effect in Cu- and Ni-doped KNbO3 in the visible and near infrared

Abstract
Nickel‐ and copper‐doped KNbO3 crystals were grown in order to investigate the photorefractive response in the visible and near infrared. Optical absorption, photoconductivity, and two‐beam coupling experiments between 515 and 1064 nm are reported. A two‐beam coupling constant at 860 nm of 1.4 and 3.2 cm−1 was measured in the nickel‐ and copper‐doped crystals, respectively.