The photoinduced absorption in Bi12TiO20 crystals is considered based on a model of two long-lived levels. Methods to
control this effect and the ways of its application are presented. New possibilities for the realization of an optical
memory system based on this effect are demonstrated.
The energy efficiency of multiwave mixing and geometrical parameters of spatial solitons in photorefractive Bi12TiO20 crystals in conditions of pulsed and continuous-wave laser excitation have been studied experimentally. It has been found that with the use of 532 nm-wavelength laser pulses switching of the photorefractive nonlinearity mechanism requires a time interval in excess of 20 - 50 ns. And saturation is observed when the duration is over 100 ns. The formation dynamics of spatial solitons in photorefractive Bi12TiO20 crystals has been analyzed using radiation of a continuous-wave He-Ne laser. It has been determined that the formation conditions and dynamics are influenced by a number of factors including the radiation input geometry of a crystal, power of the light beam, orientation of its polarization relative to the crystal axes, applied electric field and its direction.
A theoretical model has been developed for multiwave mixing in media with photorefractive nonlinearity, making it possible to describe the process of interaction between the waves in the conditions exhibiting nonlinearities of different orders with due regard for the mixing geometry. Theoretically, the process of N-wave mixing at the N - 1th-order nonlinearity has been described with the help of a band model for the photorefractive nonlinearity mechanism that includes the transitions from impurity levels within the band gap and enables description of the diffusion or drift processes in the external electric field. The energy efficiency of multiwave mixing and geometric parameters of spatial solitons in photorefractive Bi12TiO20 crystals in the conditions of pulsed and continuous laser excitation have been studied experimentally. It has been found that switching-on of the photorefractive nonlinearity mechanism with 532 nmwavelength laser pulses requires a time interval in excess of 20 - 50 ns, with saturation beyond 80 ns. The formation dynamics of spatial solitons in photorefractive Bi12TiO20 crystals has been analyzed with the use of continuous-wave radiation of a He-Ne laser. It has been determined that the formation conditions and dynamics are influenced by a number of factors including the geometry of radiation input into a crystal, power of the light beam, orientation of its polarization in the directions of the crystal axes, applied electric field and its direction.
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