P.A. Márquez Aguilar

Z-scan experiments with cubic photorefractive crystal Bi12TiO20

Abstract We present original data on experiments with cubic photorefractive crystal Bi12TiO20 under an external dc electric field in the configuration of Z-scan characterization technique. In particular, behavior of the Z-scan curves versus the external dc field, light polarization, and the (focused beam)/(uniform sample illumination) intensity ratio is reported. The data obtained are interpreted in the framework of an original theoretical analysis based on the standard drift model of the photorefractive effect and assumption of a Gaussian profile of the propagating laser beam.

Anisotropy of steady-state two-dimensional lenses in photorefractive crystals with drift nonlinearity

Abstract As a result of the original theoretical analysis in different approximations we show that the steady-state photoinduced photorefractive lens formed under an external transverse d.c. electric field by the light beam with cylindrical symmetry is essentially astigmatic. This behaviour is demonstrated in self-focusing-defocusing experiments with cubic Bi12 TiO20 photorefractive crystals at λ=633 nm. The result implies in particular that the steady-state (2+1)-dimensional spatial solitons generated in photorefractive crystals under similar conditions are to be characterized by an elliptic cross-section.

Dynamics of photoinduced lens formation in a photorefractive Bi 12 TiO 20 crystal under an external dc electric field

We report experimental results on the dynamics of formation of a photoinduced lens produced by a two-dimensional cw He–Ne Gaussian laser beam (633 nm) in a cubic Bi12TiO20 photorefractive crystal under an external dc electric field. The main features of the effect, namely, astigmatism of the dynamic lens formed, the pulse shape of the far-field response after switching on of the focused beam, inverse linear dependence of time of its growth on the beam intensity, and approximate constancy of its peak level, are explained in the framework of the analytical model for a one-dimensional Gaussian beam and numerical calculations for a two-dimensional one.

Modulation Z-scan technique for characterization of photorefractive crystals

We propose a simple single-beam configuration for characterization of the amplitude, speed of growth, and polarization properties of the photoinduced refractive-index change that is due to a drift photorefractive mechanism of nonlinearity in crystals, namely, the modulation Z-scan technique, based on the modulation of an externally applied electric field. The results of a simple theoretical model developed for one-dimensional parabolic photorefractive lens formation in this configuration are illustrated by original experiments with a semi-insulating GaAs crystal at lambda -1.06 microm.