The study of surface plasmon-polaritons interactions in metallic nanostructures has been a topic of interest during last years due to their use in various areas such as the photonics, chemistry and biology. Example of use is found in biosensors for the efficient detection of biological analyte and in nanophotonic elements for on-chip photonics.
Here, we study the interactions properties of localized surface plasmons in a hybrid waveguiding structure made of bi-dimensional array of gold nanowires vertically integrated on silicon-on-insulator waveguides across the near infrared spectrum. With the use of near-field scanning optical microscopy (NSOM) in perturbation mode, we qualitatively obtained the spectral response of such hybrid structure through intensity near field maps of the light propagation. These experimental results demonstrate that metallic nanostructures integrated on silicon are suitable for the development of localized surface plasmon integrated devices or metallic metamaterials.
We address the experimental validation of the technological feasibility and operation of the metamaterials in a guided wave configuration in the spectral domain around 1.5μm. For our experiments we considered a 2D array of 200×50×50nm gold cut wires placed on the top of a 10μm wide and 200nm thick silicon waveguide. The transmission spectral measurements performed in the spectral range between 1.25 and 1.64μm using an end-fire coupling setup, revealed a marked dip for TE polarized light, corresponding to the cut wires resonance frequency obtained by numerical modeling. No such a dip in transmission was observed for TM polarized light, i.e. when the electric filed is perpendicular to the layers interface and the orientation of the cut wires. The scanning near field optical microscopy experiments (SNOM), performed in the same spectral range, revealed for TE polarized light a strong enhancement of the electric field confined in the region between the ends of the adjacent cut wires. These results confirm the efficient excitation of the cut wires resonance in a guided wave configuration for the TE polarization. The ability for local engineering of the field interaction with the metamaterial layer and thus the control in such a way of the light flow in a guiding slab, paves the way to a novel class of photonic devices.
We investigate the potential of metallic metamaterials (MM) for integrated optic applications in the
near-infrared (λ=1.5μm). Specifically we consider a composite guiding structure made of a MM layer
over a high index slab waveguide such as silicon. In this configuration only the evanescent tail
interacts with the MM layer which acts essentially as a perturbation. Our numerical simulations show
that an array of gold coupled cut wires over a slab waveguide leads to a significant variation of the slab
effective index in the vicinity of the resonance and thus can serve as building blocks for implementing
optical functions. This geometry is compatible with current nano-fabrication technologies.