Beyond plasmons Fabry–Pérot interference as the dominant driver of PL enhancements in luminophore-plasmonic metasurface systems

Abstract In this work, we present a theoretical analysis of previously reported experimental results showing an enhancement in the photoluminescence of silicon quantum dots (QDs) due to the presence of a random metasurface of spherical gold nanoparticles. The silicon QDs are embedded in a silicon nitride matrix and supported onto a crystalline silicon substrate. Experimentally, it is observed that there is an enhancement in photoluminescence when the thickness of a layer of silicon nitride separating the random metasurface from the region where the silicon QDs are is modified. By modeling the system as a multilayer system and by considering the optical response of the metasurface as that predicted by an effective medium theory using the dipolar model, we use the transfer matrix method to analyze the electric field distribution in the region where the QDs are located, showing that the experimental enhancement is due to a Fabry–Pérot interferometric effect and not due to localized plasmon resonances induced within the gold nanoparticles. Alternatively, we propose the use of random plasmonic metasurfaces as dichroic mirrors to effectively increase the reflected light that was emitted by the QDs, exploiting the excitation of localized surface plasmon resonances within the nanoparticles and tuning the optical response of the metasurface.