  Surface Plasmon Polaritons (SPP) are exploited due to their intriguing
properties for photonic circuits fabrication and miniaturization, for surface
enhanced spectroscopies and imaging beyond the diffraction limit. However, the
excitation of these plasmonic modes by direct illumination is forbidden by
energy/momentum conservation rules. One strategy to overcome this limitation
relies on diffraction gratings to match the wavevector of the incoming photons
with that of propagating SPP excitations. The main limit of the approaches so
far reported in literature is that they rely on highly ordered diffraction
gratings fabricated by means of demanding nano-lithographic processes. In this
work we demonstrate that an innovative, fully self-organized method based on
wrinkling-assisted Ion Beam Sputtering can be exploited to fabricate large area
(cm^2 scale) nano-rippled soda-lime templates which conformally support
ultrathin Au films deposited by physical deposition. The self-organized
patterns act as quasi-1D gratings characterized by a remarkably high spatial
order which matches properly the transverse photon coherence length. The
gratings can thus enable the excitation of hybrid SPP modes confined at the
Au/dielectric interfaces, with a resonant wavelength which can be tuned either
by modifying the grating period, photon incidence angle or, potentially, the
choice of the thin film conductive material. Surface Enhanced Raman Scattering
experiments show promising gains in the range of 10^3 which are competitive,
even before a systematic optimization of the sample fabrication parameters,
with state-of-the art lithographic systems, demonstrating the potential of such
templates for a broad range of optoelectronic applications aiming at
plasmon-enhanced photon harvesting for molecular or bio-sensing.

Optics;Mesoscale and Nanoscale Physics