All-dielectric metamaterials

Abstract

The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the electric and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielectric nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), respectively, but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there has been a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all four quadrants of possible permittivities and permeabilities have been achieved using completely transparent and high-refractive-index dielectric building blocks. Moreover, an emerging class of all-dielectric metamaterials consisting of anisotropic crystals has been shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. In this Review, we present a broad outline of the whole range of electromagnetic effects observed using all-dielectric metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Finally, we discuss current challenges and future goals for the field at the intersection with quantum, thermal and silicon photonics, as well as biomimetic metasurfaces.

Self-assembled antireflection coatings for light trapping based on SiGe random metasurfaces

“…Efficient anti-reflection coatings (AR) have been intensively studied with many different approaches having been explored for this purpose [1][2][3] , such as multi-layered thinfilms 4,5 , graded index matching via surface texturing with micro-and nano-structures [6][7][8][9][10][11] , plasmonic metasurfaces [12][13][14] and more recently, metasurfaces [15][16][17][18][19][20][21] based on ordered arrays of sub-micrometric dielectric antennas (dielectric Mie resonators [22][23][24][25][26][27][28] ). Depending on the application of the AR different aspects (lowest value of the total reflectance, broad spectral range, broad acceptance angle, transparency or light trapping) determine the optimal features and fabrication method.…”

Coherent absorption of light by graphene and other optically conducting surfaces in realistic on-substrate configurations

“…Initially, researchers established the concept of metasurface, where subwavelength conducting elements (traditionally metals) enable to shape the incident beam in the spatial and temporal domains. [1][2][3] Afterwards, thanks to graphene and other two dimensional (2D) materials, which exhibit large values of the optical conductivity on a broad frequency band, remarkable non-linear optical response and tunability properties were demonstrated. [4][5][6][7][8] In addition, the conjunction of the two concepts above is expected to further boost the research field, thanks to the huge potential offered by 2D materials patterned as a metasurface [9][10][11] and by hybrid devices where a metallic metasurface is coupled to 2D conductors.…”

All-Optical Switching and Unidirectional Plasmon Launching with Nonlinear Dielectric Nanoantennas

“…In the last several years high-index dielectric nanoparticles and nanostructures [1][2][3] proved to be a promising platform for various nanophotonic applications, in particular for the design of functional nanoantennas [4][5][6], enhanced spontaneous emission [7][8][9][10], photovoltaics [11], frequency conversion [12][13][14], Raman scattering [15], and sensing [16]. The great interest in such nanostructures is caused mainly by their ability to control the electric and magnetic components of light at the nanoscale [1], while exhibiting low dissipative losses inherent to the materials with a negligible concentration of free charges [16].…”