Abstract

It is known that the optical properties of oxide crystals, such as BaTiO₃, LiNbO₃ and KNbO₃, are strongly influenced by the presence of impurity levels in the bandgap of the material. The distribution and population of these levels have been the focus of much recent research into the tailoring of photorefractive materials to respond to near infrared wavelengths compatible with compact solid-state laser diodes [1]. The impurity levels must have a sufficiently high occupation to provide significant absorption at a wavelength of interest. However, in thermal equilibrium most levels are not occupied by an excitable charge carrier and therefore do not contribute directly to the optical nonlinearity. The creation of a nonequilibrium state by optical illumination may produce a more convenient charge distribution in the material band gap levels.

© 1996 IEEE