Collective plasmonic oscillations in gold nanostrips arrays.

Excitation of collective plasmonic modes and their effect on optical behavior are experimentally and theoretically studied in 1D arrays of gold nanostrips in comparison with continuous gold films with periodically modulated profile. In strips, the angular dependence of the reflectivity demonstrates a peak at the resonance condition as opposed to a dip observed in continuous sine wave gratings. In addition, an extremely narrow feature in the reflection is observed in strips and tentatively ascribed to the bright Wood-Rayleigh anomaly. Theoretical calculations based on the combined transfer-matrix coupled-wave analysis and coordinate transformation method are shown to fit the experimental angular and spectral behavior of the plasmonic resonances. The effects are also discussed in terms of a simple equivalent circuit model.

Measuring local optical properties: near-field polarimetry of photonic block copolymer morphology.

Ultrahigh molecular weight polystyrene-b-polyisoprene block copolymers (BCs), noted for their photonic behavior, were imaged using transmission near-field scanning optical microscopy (NSOM) and NSOM polarimetry. Our improved scheme for polarization modulation (PM) polarimetry, which accounts for optical anisotropies of the NSOM aperture probe, enables mapping of the local diattenuation and birefringence (with separately aligned diattenuating and fast axes) in these specimens with subdiffraction limited resolution. PM-NSOM micrographs illuminate the mesoscopic optical nature of these BC specimens by resolving individual microphase domains and defect structures.