In this work, a trilayer graphene is used as a thin non dielectric spacer with a high index of refraction, between Au film
and Au NPs. Encouraged by the sharpness of the localized surface plasmon resonance LSPR induced by this system, we
performed sensitivity measurements to refractive index change in the surrounding medium of the sensor. The presence of
graphene led to both higher sensitivity and sharper full width at half maximum FWHM and thus higher figure of merit
FOM (2.8) compared to the system without graphene (2.1).
Numerical simulations, based on a FDTD (finite-difference-time-domain) method, of infrared light propagation for
add/drop filtering in two-dimensional (2D) Ag-SiO<sub>2</sub>-Ag resonators are reported to design 2D Y-bent plasmonic
waveguides with possible applications in telecommunication WDM (wavelength demultiplexing). First, we study optical
transmission and reflection of a nanoscale SiO<sub>2</sub> waveguide coupled to a nanocavity of the same insulator located either
inside or on the side of a linear waveguide sandwiched between Ag. According to the inside or outside positioning of the
nanocavity with respect to the waveguide, the transmission spectrum displays peaks or dips, respectively, which occur at
the same central frequency. A fundamental study of the possible cavity modes in the near-infrared frequency band is also
given. These filtering properties are then exploited to propose a nanoscale demultiplexer based on a Y-shaped plasmonic
waveguide for separation of two different wavelengths, in selection or rejection, from an input broadband signal around
1550 nm. We detail coupling of the 2D add/drop Y connector to two cavities inserted on each of its branches.
We study theoretically and experimentally the variation in localized surface plasmon resonance (LSPR) structure
(λ<sub>max</sub>=660 nm) as a function of dielectric coating thickness. The influence of the morphology and interparticle distance
on the LSPR spectra of a glass/Au NSs interface with a constant thickness of diamond (NCD) overcoating was
investigated through the calculation of theoretical transmission spectra. Ajusting the theoretical curve to experimental
LSPR spectra allowed fixing the geometry of the plasmonic interface and permitted to evaluate the change in the
wavelength at maximum absorption (λ<sub>max</sub>) as a function of the thickness of the NCD overlayers. The theoretical data
were compared with experimental ones obtained on glass/AuNSs/ NCD surface.