Anapole-Enhanced Intrinsic Raman Scattering from Silicon Nanodisks

Journal article, 2018

Enhancement of inelastic light emission processes through resonant excitation usually correlates with enhanced scattering of the excitation light, as is for example typically the case for surface-enhanced fluorescence and Raman scattering from plasmonic nanostructures. Here, we demonstrate an unusual case where a reverse correlation is instead observed, that is, we measure a multifold enhancement of Raman emission along with suppressed elastic scattering. The system enabling this peculiar effect is composed of silicon nanodisks excited in the so-called anapole state, for which electric and toroidal dipoles interfere destructively in the far-field, thereby preventing elastic scattering, while the optical fields in the core of the silicon particles are enhanced, thus, amplifying light-matter interaction and Raman scattering at the Stokes-shifted emission wavelength. Our results demonstrate an unusual relation between resonances in elastic and inelastic scattering from nanostructures and suggest a route toward background-free frequency conversion devices.