No abstract

In this paper we show that arrays of core-shell nanoparticles function as effective thin absorbers of light. In contrast to known metamaterial absorbers, the introduced absorbers are formed by single planar arrays of spherical inclusions and enable full absorption of light incident on either or both sides of the array. We demonstrate possibilities for realizing different kinds of symmetric absorbers, including resonant, ultra-broadband, angularly selective, and all-angle absorbers. The physical principle behind these designs is explained considering balanced electric and magnetic responses of unit cells. Photovoltaic devices and thermal emitters are the two most important potential applications of the proposed designs.

In this paper we theoretically study electromagnetic reflection, transmission, and scattering properties of periodic and random arrays of particles which exhibit both electric-mode and magneticmode resonances. We compare the properties of regular and random grids and explain recently observed dramatic differences in resonance broadening in the electric and magnetic modes of random arrays. We show that randomness in the particle positioning influences equally on the scattering loss from both electric and magnetic dipoles, however, the observed resonance broadening can be very different depending on the absorption level in different modes as well as on the average electrical distance between the particles. The theory is illustrated by an example of a planar metasurface composed of cut-wire pairs. We show that in this particular case at the magnetic resonance the array response is almost not affected by positioning randomness due to lower frequency and higher absorption losses in that mode. The developed model allows predictions of behavior of random grids based on the knowledge of polarizabilities of single inclusions.

We suggest a novel concept of efficient light-trapping structures for thin-film solar cells based on arrays of planar nanoantennas operating far from plasmonic resonances. The operation principle of our structures relies on the excitation of chessboard-like collective modes of the nanoantenna arrays with the field localized between the neighboring metal elements. We demonstrated theoretically substantial enhancement of solar-cell short-circuit current by the designed light-trapping structure in the whole spectrum range of the solar-cell operation compared to conventional structures employing anti-reflecting coating. Our approach provides a general background for a design of different types of efficient broadband light-trapping structures for thin-film solar-cell technologically compatible with large-area thin-film fabrication techniques.

Dielectric nanoantennas represent a new branch of nanophotonics that allows efficient control of light scattering at nanoscale. Coupled nanoantennas can guide light on a chip over large distances without radiation losses, enabling a new nanoantenna-based silicon photonics platform with enchanced functionalities for light-on-chip integration. Here, an all-optical on-chip modulator based on a one-dimensional chain of silicon nanoantennas is proposed and experimentally demonstrated in the 1.55 μm telecommunication wavelength range. A resonator, with a quality factor up to 10 4 , is designed on the basis of a chain of coupled silicon nanoantennas, each supporting the electric dipole Mie resonance. Wafer-level fabrication of the nanoantennas is realized using CMOS compatible photolithography. High-speed modulation of the cavity mode is experimentally demonstrated via optical injection of free electrons and holes using a pulsed laser. The modulator is shown to have a response time of 50 ps and modulation depth beyond 25 dB, with 10 dB switching power being as low as ∼50 fJ. Low power and high-speed switching of the proposed device combined with the large-scale fabrication capabilities pave the way to applications of this dielectric nanoantenna-based approach to industrial on-chip photonics.