Grain orientation governed third-order optical nonlinearity in indium tin oxide films

We investigate the third-order optical nonlinearity in indium tin oxide (ITO) films of different grain orientations grown at various sputtering powers by magnetron sputtering technique. The nonlinear refractive index n2 and nonlinear absorption coefficient beta in ITO films were determined using the Z-scan method, and were found to be significantly influenced by grain orientations. Specially, n2 and beta in ITO films of near pure (222) crystalline orientation prepared at 90 W have the maximum values than in the others films but of polycrystalline orientations fabricated at different powers. By analyzing the relation between crystalline orientation of ITO films and n2 (beta), the third-optical nonlinearity in ITO films governed by the crystalline orientation (222) was concluded. The results give direction to fabricate the ITO films of the optimized third-order optical nonlinearity for highperformance nonlinear optical devices.