Spatial soliton tunneling in longitudinally modulated optical lattices

Abstract

We study numerically the dynamics of a beam in a focusing photorefractive nonlinear optical lattice with a longitudinal potential barrier. Such kind of lattice with the refractive index modulation in both transverse and longitudinal directions can be realized by induced optically in photorefractive crystals. Different soliton states are found with different position of the input pulse, which exhibits compression or splitting during transmission. The results also indicate that the intensity of a beam and the transverse modulation frequency of lattice can affect apparently the ability of tunneling. For the same lattice depth, the smaller the transverse frequency of the lattice is and the higher peak intensity the soliton possesses, the easier the soliton tunnels through. However, when we increase the frequency of optical lattice, the optical beam can successfully pass through the barrier for the relatively small value of lattice depth as well. Otherwise, the beam splits into some filaments when the lattice depth is large enough. In addition, we find that beam can exhibit the behavior of oscillation during transmission and the oscillation frequency of spatial soliton is influenced by the biased field.