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Enhanced nonlinear optical processes in nanostructured materials

Authors Lu, Weixin
Issue Date 2011
Summary The nonlinear optical properties of three nano-structured material systems are investigated: one-dimensional semiconductor photonic crystals (PC), gold-nanoparticle containing dielectric thin films, and dye-doped one-dimensional (1D) dichromated gelatin (DGC) photonic bandgap structures. A theoretical simulation of simultaneous second harmonic generation (SHG) and third harmonic generation (THG) in 1D nonlinear PC is used to design appropriate PC structures to realize phase-matched SHG and THG using ZnS as the nonlinear layer. Dramatic simultaneous enhancement of SHG and THG in forward and backward directions from a 1D ZnS/YF3 PC structure have been observed. The conversion efficiencies of SHG and THG in forward and backward directions are in good agreement between the experimental results and theoretical simulations. Gold nanoparticle doped glass thin film ((SiO2)1-x-Au-(TiO2)x) was fabricated by the sputtering and thermal annealing process. The dispersion of the third order susceptibility of these films is measured by the Z-scan technique. The nonlinear susceptibilities (real and imaginary part) of these samples are observed to show strong dispersion near the surface plasma resonance peak. And our results are compared to those obtained in degenerate four wave mixing experiment. PC structures were fabricated in dichromate gelatin (DCG) emulsions using a two-beam holographic interference. The dye-doped 1D DCG PC was demonstrated to exhibit efficient optically pumped lasing near the band edge. The high density of modes near the band edge of photonic crystal contributes to the realization of low-threshold lasing.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2011
Language English
Format Thesis
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