Mesoporous silica layer on plasmonic array: light trapping in a layer with a variable index of refraction

Abstract

Mesoporous silica layers with open and accessible mesopores were fabricated on aluminum nanoparticle arrays. The system can support plasmonic-photonic hybrid modes that are radiatively coupled surface plasmon polaritons in the nanoparticles. The coupling is mediated either by diffraction in the plane of the array or by waveguiding in the dielectric silica layer covering the array. Upon irradiation of an array with visible light, these hybrid modes are excited and appear as sharp spectral dips in optical transmission, a manifestation of light trapping in the system. The porous nature of the layers can be taken advantage of, via pore infiltration, to facilitate control over the layer’s refractive index. We demonstrated tuning in the wavelength and spatial distribution of trapped light in the system.