Under certain conditions, light incident on a metallic particle can excite a collective electron excitation known as a surface plasmon-polariton (SPP), a term that describes the nature of the interaction, which involves the metal’s free electrons (plasma) and light-induced polarization (polariton).
The surface plasmon mode is generally characterized by intense electric fields that decay exponentially away from the interface between the metal and the surrounding environment. Due to their unique properties, plasmonic systems have found a broad range of applications in various areas of science, including nanobiotechnology and biomedicine, where plasmons can be used for biosensing or for monitoring of biological cells and tissues. In optics, the large field strengths of surface plasmons can dramatically enhance a variety of phenomena, such as Raman scattering, photoluminescence and nonlinear optical effects. Also, from a more fundamental perspective, plasmonic systems constitute a very unique platform. Using two or more metallic elements in fact, it is possible to localize the electromagnetic radiation well below the limit of diffraction and generate electric field spots that are hundred times larger the incident radiation. These local hot-spots can be confined in deeply sub-wavelength volumes of the order of few cubic nanometers, making the light “sensitive” to the sub-atomic realm. In this regime, the classical description of light-matter interactions is not accurate enough and quantum aspects must be taken into account. The intrinsic multi-scale nature of such systems however makes their numerical investigation a real challenge.
Our work aims to develop novel numerical tools and theoretical methods to tackle multi-scale light-matter interaction problems. Plasmonic structures characterized by extremely small gaps are valuable candidates for achieving enhanced light-matter interactions, efficient nonlinear and quantum effects, thus leading to exotic new functionalities and applications.