Anomalous spectral scaling of light emission rates in low-dimensional metallic nanostructures

The strength of light emission near metallic nanostructures can scale anomalously with frequency and dimensionality. We find that light-matter interactions in plasmonic systems confined in two dimensions (e. g., near metal nanowires) strengthen with decreasing frequency owing to strong mode confinement away from the surface-plasmon frequency. The anomalous scaling also applies to the modulation speed of plasmonic light sources, including lasers, with modulation bandwidths growing at lower carrier frequencies. This allows developing optical devices that exhibit simultaneously femtosecond response times at the nanometer scale, even at longer wavelengths into the mid-IR, limited only by nonlocal effects and reversible light-matter coupling.