Ultrafast and large third-order optical nonlinearity of porous nanosized poly-crystal LiNbO3film

The porous nanosized poly-crystal LiNbO 3 film on the fused SiO 2 substrate was prepared by using r.f. sputtering method. The microstructure and the third-order optical nonlinearity of the film were investigated. The size of the micro-crystal grains was in the range of 110-160 nm, and the average pore size was 80 nm. The magnitude of ultrafast response χ (3) of the sputtered thin LiNbO 3 film at 830 nm wavelength was estimated to be as large as 1.9×10 -8 esu, which is 4 orders of magnitude larger than that of LiNbO 3 single crystal.