Plasmon Enhanced Second Harmonic Generation from ZnO Nanofilms on Vertical Au Nanorod Arrays

Abstract

Vertically aligned gold nanorod arrays have attracted much attention for their fascinating optical properties. Different from longitudinal surface plasmon wavelength (LSPW) and edge-to-edge spacing of gold nanorods, the role of gold nanorod diameter in plasmonic enhancement ability of vertical gold nanorod arrays has rarely been explored. In this work, we selected gold nanorods with similar LSPW but two different diameters (22 and 41 nm), the optical properties of which are dominated by absorption and scattering cross sections, respectively. The vertically aligned arrays of these gold nanorods formed by evaporation self-assembly are coupled with nonlinear ZnO nanocrystal films spin-coated on their surfaces. It was found that the gold nanorod array with a larger diameter can enhance the second harmonic generation (SHG) of ZnO nanofilm by a factor of 27.0, while it is about 7.3 for the smaller gold nanorod array. Theoretical simulations indicate that such stronger enhancement of the larger vertical gold nanorod array compared with the smaller one is due to its stronger scattering ability and greater extent of near-field enhancement at SHG fundamental wavelength. Our work shows that the diameter of gold nanorods is also an important factor to be considered in realizing strong plasmon enhancement of vertically aligned gold nanorod arrays.

Fractional Photoconduction and Nonlinear Optical Behavior in ZnO Micro and Nanostructures

“…Third-order optical nonlinearities can be controlled by irradiance, polarization, and concentration of different sizes and morphologies of crystals in ZnO nanostructures [45]. In addition, it has been reported that ZnO nanocrystals, nanofilms, nanowires [46], and bulk structures can be used as nonlinear media to obtain higher-frequency conversion efficiencies from nonlinear effects [47,48]. Also, various ZnO-based nanohybrids have been examined for the enhancement of their nonlinear optical interactions [49][50][51][52][53][54][55][56].…”

Special Issue: State-of-the-Art Nanophotonic and Optical Nanomaterials in China

“…This Special Issue aims to provide an overview of the current advances in nanophotonic and optical nanomaterials in China and to prompt new interest in this field. The collected eight articles [1][2][3][4][5][6][7][8] highlight the latest progress in nanophotonics and materials science, including developments of novel nanomaterials and ingenious nanoscale designs. These contributions may unveil new opportunities to control light, provide effective ways to optimize targeted performances, and have important implications for novel photonic devices operating beyond the diffraction limit.…”

“…Notably, nanomaterial structures play important roles in the optimization of device performances. In this context, vertically aligned Au nanorod arrays with two different diameters were prepared by Ma et al based on the evaporation self-assembly method, which was used to realize a strong plasmon enhancement on the second harmonic generation [3]. Yu et al proposed a novel method to prepare high dispersibility silver nano-ink-filled particles, in which the addition of filling particles could effectively improve its electrical conductivity without significantly changing the metal solid content in the ink [4].…”