An effective semianalytical method for analyzing the Cartesian multipole contributions in light transmission and reflection spectra of flat metasurfaces composed of identical nanoparticles is developed and demonstrated. The method combines numerical calculation of metasurface reflection and transmission coefficients with their multipole decompositions. The developed method is applied for the multipole analysis of reflection and transmission spectra of metasurfaces composed of silicon nanocubes or nanocones. In the case of nanocubes, we numerically demonstrate a “lattice invisibility effect,” when light goes through the metasurface almost without amplitude and phase perturbations with the simultaneous excitation of nanoparticles' multipole moments. The effect is realized due to destructive interference between the fields generated by the basic multipole moments of nanoparticles in the backward and forward directions. For metasurfaces composed of conical nanoparticles, we show that their transmission coefficient does not depend on illumination direction. In contrast, the reflection and absorption can be different for the illumination from different metasurface sides, which is associated with the excitation of different multipoles. We believe our results could be useful for analysis and understanding of the electromagnetic properties of nanoparticle arrays and pave the way for the design of novel metasurfaces for various optical applications.

The ongoing quest for ultra‐compact optical devices has reached a bottleneck due to the diffraction limit in conventional photonics. New approaches that provide subwavelength optical elements, and therefore lead to miniaturization of the entire photonic circuit, are urgently required. Plasmonics, which combines nanoscale light confinement and optical‐speed processing of signals, has the potential to enable the next generation of hybrid information‐processing devices, which are superior to the current photonic dielectric components in terms of speed and compactness. New plasmonic materials (other than metals), or optical materials with metal‐like behavior, have recently attracted a lot of attention due to the promise they hold to enable low‐loss, tunable, CMOScompatible devices for photonic technologies. In this review, we provide a systematic overview of various compact optical modulator designs that utilize a class of the most promising new materials as the active layer or core— namely, transparent conducting oxides. Such modulators can be made low‐loss, compact, and exhibit high tunability while offering low cost and compatibility with existing semiconductor technologies. A detailed analysis of different configurations and their working characteristics, such as their extinction ratio, compactness, bandwidth, and losses, is performed identifying the most promising designs.

Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes.

We propose several planar layouts of ultra-compact plasmonic modulators that utilize alternative plasmonic materials such as transparent conducting oxides and titanium nitride. The modulation is achieved by tuning the carrier concentration in a transparent conducting oxide layer into and out of the plasmon resonance with an applied electric field. The resonance significantly increases the absorption coefficient of the modulator, which enables larger modulation depth. We show that an extinction ratio of 46 dB/µm can be achieved, allowing for a 3-dB modulation depth in much less than one micron at the telecommunication wavelength. Our multilayer structures can be integrated with existing plasmonic and photonic waveguides as well as novel semiconductor-based hybrid photonic/electronic circuits.