Raman scattering governed by dark resonant modes in silicon nanoparticles

Analyzing the modal content of resonant nanostructures using optical methods often becomes a sophisticated problem because of hidden dark resonances, which are uncoupled with far-field modes. The common methods of dark modes spectroscopy base on electron beam systems, such as cathodo-luminescence and, thus, are not very convenient in use. We suggest utilizing Raman spectroscopy to reveal the full modal structure of nanoresonators. The suggested approach is tested on silicon nanoparticles placed on top of gold substrate. It allows detecting magnetic quadrupole modes, which are hard to observe with common dark-field spectroscopy. The experimental results are verified with numerical simulations.