Two-dimensional arrays of silver nanocylinders fabricated by electron-beam lithography are used to demonstrate plasmon-enhanced near-green light emission from nitride semiconductor quantum wells. Several arrays with different nanoparticle dimensions are employed, designed to yield collective plasmonic resonances in the spectral vicinity of the emission wavelength and at the same time to provide efficient far-field scattering of the emitted surface plasmons. Large enhancements in peak photoluminescence intensity (up to a factor of over 3) are measured, accompanied by a substantial reduction in recombination lifetime indicative of increased internal quantum efficiency. Furthermore, the enhancement factors are found to exhibit a strong dependence on the nanoparticle dimensions, underscoring the importance of geometrical tuning for this application.

A detailed experimental and theoretical study of the plasmonic properties of silver nanoparticle arrays as a function of nanoparticle height is presented. Specifically, several square periodic arrays have been fabricated by electron beam lithography and characterized via transmission spectroscopy measurements. The same arrays have also been numerically investigated via finite-difference time-domain calculations of their scattering and absorption cross sections and steady-state field intensity distributions. The results of this study show that the collective plasmonic resonances of these arrays can be effectively blueshifted by increasing the nanoparticle height, while at the same time maximizing the average field enhancement in the substrate and maintaining small absorption losses. This approach can therefore be used to extend the spectral reach of lithographically defined metallic nanoparticle arrays for practical applications such as light-emission efficiency enhancement.

Diffractive arrays of silver nanocylinders are used to increase the radiative efficiency of InGaN/GaN quantum wells emitting at near-green wavelengths. Large enhancements in luminescence intensity (up to a factor of nearly 5) are measured when the array period exceeds the emission wavelength in the semiconductor material. The experimental results and related numerical simulations indicate that the underlying mechanism is a strong resonant coupling between the light-emitting excitons in the quantum wells and the plasmonic lattice resonances of the arrays. These excitations are particularly well suited to light-emission-efficiency enhancement, compared to localized surface plasmon resonances at similar wavelengths, due to their larger scattering efficiency and larger spatial extension across the sample area.

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The coupling between excited electron-hole pairs in semiconductor active layers and surface plasmon polaritons in metallo-dielectric stacks is investigated. These structures can be used to engineer the surface-plasmon dispersion properties so as to introduce tunable singularities in the photonic density of modes, and hence in the recombination rate of nearby active media. A detailed theoretical study of this effect is presented together with the experimental demonstration of geometrically tunable increased recombination in GaN / AlGaN quantum wells via near-UV photoluminescence measurements. If combined with a suitable geometry to efficiently scatter the emitted surface waves into radiation, this approach can be used for light-emission efficiency enhancement at tunable wavelengths.