Extraordinary Optical Transmission through ZnO Nanowire Waveguides in Silver
Huizhong Xu, St. John’s College of Liberal Arts and Sciences, Department of Physics; Undergraduate Students: Spencer Mamer, Kimberly Singh, Orlando Lopez, Ashley Tucker
The development of efficient light-guiding devices on the nanoscale has attracted great attraction in the recent years due to their potential applications in a variety of fields such as near-field scanning optical microscopy, single molecule spectroscopy, and high-resolution optical lithography. Among the various approaches studied, dielectric nanowaveguide is particularly interesting for its simplicity and promising properties. It has been shown that a propagating mode can in principle exist inside a waveguide of arbitrary small size if the dielectric constants of the cladding metal and the dielectric core are matched. One possible pairing of dielectric and metal is ZnO and silver respectively. Using finite element simulations, we have recently shown that efficient guiding of 488 nm light can be obtained for a waveguide diameter of 40 nm and a silver film thickness of 100 nm. Here, we experimentally demonstrate that strong resonant transmission of 500 nm light through ZnO nanowire waveguides in a silver film can be achieved for waveguide diameters around 40 nm. We also perform finite element simulations and attribute the observed resonant transmission to the unique material combination enabling a large cutoff wavelength inside the waveguide and the excitation of localized surface plasmons at the end interfaces of the waveguide.