Dielectric and semiconductor nanoantennas

Over the last decade the research in resonant nanophotonics was mainly focused on metallic nanostructures maid out of plasmonic materials such as gold and silver. Plasmonic nanoparticles may provide high field localization and... [ view full abstract ]

Over the last decade the research in resonant nanophotonics was mainly focused on metallic nanostructures maid out of plasmonic materials such as gold and silver. Plasmonic nanoparticles may provide high field localization and enhancement at their resonances which stimulated a discussion of multiple potential applications of resonant nanophotonics for future technologies. However, at visible and near-IR frequencies these resonances are accompanied by strong Ohmic losses, generating a substantial heat which reduces the stability of plasmonic nanostructures at elevated light intensities and is undesirable for many applications. This significantly limits the areas of practical applications of plasmonics. Recently a new branch of resonant nanophotonics has emerged which has a potential to complement the existing plasmonic approaches and solve the major problem of losses. It is based on optical Mie resonances in high-refractive index dielectric and semiconductor nanoparticles [1]. In contrast to the case of plasmonic nanoparticles, the resonances in high-index dielectric nanoparticles are related to oscillations of bound rather than free charges and thus can be generated without any losses in transparent dielectric or semiconductor materials. In my talk, I will review a recent progress in this rapidly developing field and present several new results from our team revealing the potential of dielectric and semiconductor nanoantennas for various applications. This will include resonant near-field interactions for magnetic and electric near-field concentration, long-range low-loss near-field energy transport and fluorescence enhancement. I will also demonstrate various far-field nanoantenna phenomena related to directional light scattering by single nanoantennas and phased nanoantenna arrays (metasurfaces) whose properties can be precisely controlled by engineering the nanoantenna radiation patterns. In particular I will demonstrate metasurfaces, which can efficiently bend light at extremely high angles (above 80 degrees) and can be used to design visible-range flat lenses with record-high numerical aperture of 0.99. In addition I will discuss different material platforms for dielectric nanoantenna and show how various materials can be used to make active and nonlinear nanoantennas in different spectral ranges.

References:

1) A. I. Kuznetsov et al., “Optically resonant dielectric nanostructures”, Science 354, aag2472 (2016).