Tomsk State University of Control Systems and Radioelectronics, Russia

Periodic optical waveguide systems (waveguide arrays, WA`s) exhibit some unique features in the linear and nonlinear propagation of light. In the nonlinear regime it can result in the light localization within WA´s in the form of discrete spatial solitons. Both, the stationary and dynamic waveguide systems may be formed in photorefractive crystals like lithium niobate (LiNbO3). The photorefractive nonlinear response allows obtaining the discrete spatial soliton regimes at optical powers of microwatt range. To form waveguide elements in crystal media, the direct laser writing with radiation of femtosecond lasers may be used. The main aim of this work is experimental demonstration of nonlinear light propagation within one-dimensional laser-written WA in photorefractive LiNbO3. We show that inter-waveguide coupling may change due to WA heating that gives the way for the tailoring characteristics of the nonlinear self-action of light beams within the WA. The waveguide structure studied has been formed in X- cut wafer of Fe:LiNbO3 by laser writing using a Ti:Sapphire femtosecond laser at wavelength of 800 nm and 100 - 150 fs pulse length. The pulse energy obtained 1 mJ. The spatial period of the WA is 15 m and there is not any discrete diffraction of light within it. To increase the inter-waveguide coupling, we heat it to 900 degrees which results in linear and nonlinear discrete diffraction of light at single-element excitation configuration.