Dmitry Morits

Effective electric and magnetic properties of metasurfaces in transition from crystalline to amorphous state

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 magnetic-mode 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.

Enhanced efficiency of light-trapping nanoantenna arrays for thin-film solar cells

We suggest a new type of efficient light-trapping structures for thin-film solar cells based on arrays of planar nanoantennas operating far from their plasmon resonances. The operation principle of our structures relies on the excitation of collective modes of the nanoantenna arrays whose electric field is localized between the adjacent metal elements. We calculate a substantial enhancement of the short-circuit photocurrent for photovoltaic layers as thin as 100-150 nm. We compare our light-trapping structures with conventional anti-reflecting coatings and demonstrate that our design approach is more efficient. We show that it may provide a general background for different types of broadband light-trapping structures compatible with large-area fabrication technologies for thin-film solar cells.

Isotropic negative refractive index at near infrared

In this paper we suggest and study a metamaterial composed of non-magnetic spherical particles, which according to both approximate analytical theory and exact simulations possesses an isotropic negative refractive index in the near-infrared frequency range. The effect of negative refraction has been confirmed by full-wave simulations of the Gaussian beam diverted by a metamaterial prism. The disagreement between predictions of the theory for an infinite lattice and the results of full-wave simulations for the prism is discussed.

Multifunctional stretchable metasurface for the THz range

In this paper we propose and study some electromagnetic properties of a thin composite layer formed by metal stripes of resonant length located on two sides of an elastic polymer film. We show that in the THz range the structure offers multiple functionalities such as high sensitivity to applied mechanical strain and polarization transformation properties. We suggest a method of fabrication for such composite layers, prepare the experimental sample and measure the dependence of the transmission coefficient on stretching.

Efficient method of moments analysis of an infinite array of triangular nanoclusters in the optical frequency range

This paper provides an efficient Method-of-Moments solution for an infinite doubly periodic array of magnetic nanoclusters. Multiple-scattering based Macro Basis Function approach is employed to obtain a reduced representation of equivalent current distributions. The incomplete QR algorithm is exploited to reduce the computation time and memory required to solve the reduced system of equations. The accuracy and efficiency of the combined approach are investigated for an infinite doubly periodic array of magnetic nanoclusters composed of eight silver triangular particles at optical frequencies.

Effective response of metasurfaces: From periodical to random structures

In this presentation we discuss the results of our recent theoretical studies of electromagnetic reflection, transmission, and scattering properties of periodic and random arrays of particles which exhibit both electric-mode and magnetic-mode 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 paticles. The study is relevant to understanding of electromagnetic response of complex composite layers, especially manufactured using self-assembly techniques.

Efficient method of moments analysis of infinite and finite arrays of magnetic nanoclusters in the optical frequency range

Multiple-scattering-based macro basis function approach complemented with the incomplete QR algorithm provides an efficient method of moments solution for the analysis of infinite and finite arrays of magnetic and magneto-electric nanoclusters. The efficiency and the accuracy of the combined approach have been validated with respect to the brute-force implementation of the method of moments and the finite element method-based commercial simulator Ansoft HFSS, respectively, for an infinite doubly periodic array of magnetic nanaoclusters in the optical frequency range.