Anapole-Enhanced Intrinsic Raman Scattering from Silicon Nanodisks

Abstract

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.

Low‐Loss Hybrid High‐Index Dielectric Particles on a Mirror for Extreme Light Confinement

“…The nanodisks were carved from high‐quality polycrystalline silicon films deposited by low‐pressure chemical vapor deposition followed by annealing at high‐temperature (1000 °C) in a nitrogen atmosphere. This ensured low intrinsic absorption, as required to realize highly efficient scattering nanostructures . The same quality of material cannot be directly deposited on a metallic mirror and patterned using lithographic methods since both Au or Ag films cannot withstand the high processing temperatures required.…”

“…This ensured low intrinsic absorption, as required to realize highly efficient scattering nanostructures. [45] The same quality of material cannot be directly deposited on a metallic mirror and patterned using lithographic methods since both Au or Ag films cannot withstand the high processing temperatures required. This renders our fabrication method unique and, importantly, allows for prefunctionalization of the metallic mirror prior to dispersion of the Si nanodisks.…”

Toroidal Dipole Resonances in All‐Dielectric Oligomer Metasurfaces

“…[24] Strong toroidal resonances could also be realized via the all-dielectric route, with several works already dedicated toward this prospect, either theoretically [25][26][27][28][29] or experimentally. [33] Dielectric resonators are efficient tools for obtaining the anapole state, with plenty of potential applications being presented, including electric field enhancement, [34] passive cloaking, [35] nanolasers, [36] enhanced Raman scattering, [37] magnetoelectric field separation, [38] nonlinear harmonic generation, [39] etc. [33] Dielectric resonators are efficient tools for obtaining the anapole state, with plenty of potential applications being presented, including electric field enhancement, [34] passive cloaking, [35] nanolasers, [36] enhanced Raman scattering, [37] magnetoelectric field separation, [38] nonlinear harmonic generation, [39] etc.…”

Additional enhancement of SERS effect by a surface wave in photonic crystal

“…Because of its intrinsically low intensity, large efforts are made to enhance the Raman signal. This enhancement can be carried out by photonic microresonators . The highest sensitivity is reached with the surface‐enhanced Raman spectroscopy (SERS) method, which allows the detection of small amounts of matter down to single molecules .…”