Scattering by plasmon resonances of metallic nanoparticles can be tailored by particle material, size, shape, and local as well as long-range order. In this presentation we discuss a series of experiments in which long-range Fano-type coupling between grating resonances and localized surface palsmon (LSP) resonances were studied using second harmonic excitation (SH-E) spectroscopy. By tuning the excitation wavelength of a femtosecond laser and measuring the relative second harmonic (SH) signal we demonstrated that when long-range grating resonances spectrally overlap with those of the LSPs, electromagnetic field enhancement occurs on the surface of the nanoparticles leading to an increase in nonlinear scattering. This effect has been demonstrated for periodic arrays of monomers and dimers, bi-periodic antenna arrays for multi-spectral focusing to a single point, and chirped nanoparticle structures for broadband field enhancement. Results are supported by finite difference time domain simulations showing that electromagnetic fields are enhanced close on the surface of the nanoparticles when long-range structural resonances are excited. These studies have revealed design principles for engineering the interplay of photonic and plasmonic coupling for future linear and nonlinear plasmonic devices.
The ability to reproducibly and accurately control light matter interaction on the nanoscale is at the core of the field of
optical biosensing enabled by the engineering of nanophotonic and nanoplasmonic structures. Efficient schemes for
electromagnetic field localization and enhancement over precisely defined sub-wavelength spatial regions is essential to
truly benefit from these emerging technologies. In particular, the engineering of deterministic media without translational
invariance offers an almost unexplored potential for the manipulation of optical states with vastly tunable transport and
localization properties over broadband frequency spectra. In this paper, we discuss deterministic aperiodic plasmonic and
photonic nanostructures for optical biosensing applications based on fingerprinting Surface Enhanced Raman Scattering
(SERS) in metal nanoparticle arrays and engineered light scattering from nanostructured dielectric surfaces with low
refractive index (quartz).