Artificial materials have recently played a leading role in the debate surrounding the design and fabrication of novel devices aimed at enhancing both linear and nonlinear light-matter interactions. A fresh approach to this debate may be provided by materials operating in the vicinity of their plasma frequencies, where they exhibit extremely low permittivity values (also known as epsilon-near-zero condition), which can be achieved either in natural or engineered materials, leading to singularity-driven enhancements of the local field and boosting of nonlinear and quantum optical phenomena. Epsilon-near-zero materials in fact display unprecedented values of field enhancement without resorting to the inclusion of any active material or resonant condition, therefore showing an incredible potential to improve nonlinear interactions, that range from harmonic generation to optical bistability and switching, from stimulated Raman scattering to soliton formation, to name just a few.
Nonlinear Optics in Nanostructures
Solid understanding of nonlinear optical phenomena at the nanoscale is the first, necessary step toward the design and development of reconfigurable devices based on nanostructures. Design principles based solely on the linear properties of nanostructures lead to the realization of static functionalities. The next and natural progress is to provide fast (nanosecond or less), inertial-less (no moving parts), and reliable tunability to these functionalities. This can be achieved by exploiting the nonlinear properties of nanostructures, whose signature can be modulated by varying physical parameters like light intensity, temperature, etc. and may also provide important information about the surrounding environment. Areas of interest include: nanoantennas for nanomixers, ultrafast nonlinearities with ultrathin nanostructures, optical limiting for laser eye protection, all-optical switches, all-optical beam steering, bistable nanoscale devices, computational electromagnetics and modeling techniques for nanostructures like metamaterials and metasurfaces.
The most critical challenge for high-bandwidth and low-power-consumption photonic devices is the reduction of the physical dimensions of photonic components down to the nanoscale, beyond the diffraction limit. Surface plasmons are collective oscillations of free electrons at metal-dielectric interfaces that are usually excited by photons. Localized and propagating surface plasmons have been indicated as possible solutions for nanoscale photonics and for bridging the gap between photonics and electronics, thanks to the pronounced abilities of confining light in sub-wavelength volumes and enhancing the electric field. In addition, plasmonic structures – such as nanoparticles and waveguides - are extremely sensitive to the surrounding environment and lend themselves naturally to sensing and detection applications.
Graphene and other 2D materials
Graphene is a one-atom-thick lattice of carbon atoms with semi-metallic electronic behavior, zero band-gap and linear energy-momentum dispersion relation, flat optical absorption from ultraviolet to infrared, and excellent mechanical properties. I am particularly interested in the nonlinear and tunable electromagnetic response of graphene and other 2D materials, such as MoSe2 and their with photonic platforms (e.g., waveguides, gratings, photonic crystals) and nanostructures. Possible applications include but are not limited to: ultrathin and optically-transparent microwave and rf devices, such as antennas, polarizers and filters, tunable photonic devices (switches, tunable filters, modulators), ultrafast pulsed lasers, ultrathin mixers.