The design, fabrication, and characterization of an upconversion-luminescence enhancer based on a two-dimensional plasmonic crystal are described. Full-wave finite-difference time domain analysis was used for optimizing the geometrical parameters of the plasmonic crystal for maximum plasmon activity, as signified by minimum light reflection. The optimum design produced >20× enhancement in the average electromagnetic field intensity within a one-micron-thick dielectric film over the plasmonic crystal. The optimized plasmonic upconverter was fabricated and used to enhance the upconversion efficiency of sodium yttrium fluoride: 3% erbium, 17% ytterbium nanocrystals dispersed in a poly(methylmethcrylate) matrix. A thin film of the upconversion layer, 105 nm in thickness, was spin-coated on the surface of the plasmonic crystal, as well as on the surfaces of planar gold and bare glass, which were used as reference samples. Compared to the sample with a planar gold back reflector, the plasmonic crystal showed an enhancement of 3.3× for upconversion of 980-nm photons to 655-nm photons. The upconversion enhancement was 25.9× compared to the same coating on bare glass. An absorption model was developed to assess the viability of plasmonically enhanced upconversion for photovoltaic applications.
Enhancement of electromagnetic field by two dimensional arrays of rectangular and cylindrical nanopillars of both gold
and silver metals arranged in either square or triangular lattices was investigated. We simulated these gratings by 3D
Finite Difference Time Domain (3D-FDTD) method in visible and near infrared (NIR) wavelengths regime and
investigated field enhancement by exciting surface plasmon polaritons (SPPs) as a function of geometrical parameters of
grating. It was found that the geometrical grating parameters such as period, shape, thickness and size can be tuned for
excitation of SPPs at particular frequency of interest. The tuned grating would lead to an electric field intensity
enhancement by greater than 100× near the grating surface due to excitation of SPPs. Cylindrical gratings tuned for 750
nm at zero degree incident angle showed that the thickness of grating is the most sensitive geometrical parameter of
resonance. Furthermore, triangular lattice gratings have wider bandwidth of resonance than square lattice gratings.
Meanwhile, wavelength versus incident angle diagram showed that the enhancement was highly sensitive with angle of