Light pulse manipulation in Sn 2 P 2 S 6

Abstract Acceleration and deceleration of light pulses when writing a refractive index grating in Sn 2 P 2 S 6 is described. It is shown that in crystals with two types of movable charge carriers short pulses are accelerated while long pulses are delayed or vice versa, depending on the orientation of the polar axis

Nearly degenerate two-beam coupling in photorefractive crystals with two species of movable carriers

Two-beam intensity coupling is calculated for photorefractive crystals with two types of movable charge carrier in the undepleted-pump approximation. The analytical expressions are derived for the temporal evolution of the space-charge field; for weak coupling they are used for calculation of the transmitted beam intensities. The results of the calculation are compared with the experimental observations in photorefractive tin hypothiodiphosphate (Sn 2 P 2 S 6 ). All experimental data are in reasonable quantitative agreement with the calculations. © 1998 Optical Society of America [S0740-3224(98

Explicit solutions of the four-wave mixing model

The dynamical degenerate four-wave mixing is studied analytically in detail. By removing the unessential freedom, we first characterize this system by a lower-dimensional closed subsystem of a deformed Maxwell-Bloch type, involving only three physical variables: the intensity pattern, the dynamical grating amplitude, the relative net gain. We then classify by the Painleve' test all the cases when singlevalued solutions may exist, according to the two essential parameters of the system: the real relaxation time tau, the complex response constant gamma. In addition to the stationary case, the only two integrable cases occur for a purely nonlocal response (Real(gamma)=0), these are the complex unpumped Maxwell-Bloch system and another one, which is explicitly integrated with elliptic functions. For a generic response (Re(gamma) not=0), we display strong similarities with the cubic complex Ginzburg-Landau equation.Comment: 16 pages, J Phys A Fast track communication, to appear 200

A new instability of counter-propagating waves in BaTiO3?

International audienceThe self-development of a strong reflection grating in a BaTiO3 sample illuminated with two mutually incoherent counter-propagating light waves is reported. The two transmitted waves diffracted from this grating become partially mutually coherent