Nanophotonics, encompassing plasmonics, metamaterials and functional photonic materials, has emerged as a rapidly expanding new field for materials and devices research in the past few years. As a result, important advances in fields such as photovoltaics, nano-optical sensors, enhanced information storage, light-emitting devices and photocatalysis have benefitted from a deeper understanding and improved control of light-matter interactions on the nanoscale. In particular, optical nanoantennas are capable of concentrating and enhancing optical fields to the nanometer-scale and receiving and transmitting optical signals in a highly directional way, which challenges existing technological limits such as gound-breakingly pushing the hard-disck storage densities into 1Tb/inch2. Monopole-nanoantennas, which consist of quarter-wavelength-long vertically oriented metal rods placed on a conductive ground plane, are of great interest due to their ease of fabrication and large signal directivity and gain.Here, we demonstrate how the design of gold monopole-nanoantenna arrays affects the enhancement and localization of optical frequency electric fields in underlying semiconducting conjugated polymer(poly(3-hexylthiophene), P3HT) films, both experimentally and theoretically. We successfully fabricate a gold nanoantenna/P3HT/silver film monopole-nanoantenna array system where the silver film acts as the conductive ground plane. Significant absorption enhancement in polythiophene is obtained which is also validated by agreement with full-field electromagnetic simulation data. Under logitudinally polarized excitation, light is strongly localized both at the tip of the gold nanoantenna and in the underlying P3HT thin film compared with the fact that light is only localized on the surface of the nanoantenna under transverse polarization. We also suggest that there is an image plane effect between the nanoantenna and the underlying metal ground plane which causes the system to behave like a dipole antenna with large field intensity enhancement in the P3HT 'gap' region when light is polarized longitudinally.

Light-management in ultrathin conjugated polymer films on metallic ground planes

244th National Meeting (2012)

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