Subwavelength terahertz imaging with graphene hyperlens

The terahertz (THz) technology provides with striking possibilities for defense, spectroscopy and biomedical imaging [1]. However, a large wavelength (λ > 10 μm) does not allow resolving tiny details. One of the solutions is a lens consisting of a material with the hyperbolic dispersion (hyperlens) [2]. Direct scaling of optical designs to the THz range is not possible, since metal’s negative permittivity becomes too large in absolute value. This is why the employment of new materials is required.In this contribution we report for the first time the graphene wire medium based hyperlens. Stacking multiple structured graphene layers provides the hyperbolic dispersion. To restore the graphene wire medium dispersion diagrams and isofrequency contours we developed a rigorous numerical method. It also gives the possibility to calculate the permittivity tensor and to check the applicability of the homogeneous medium approach.Our numerical simulations in COMSOL and CST Microwave Studio confirm the subwavelength imaging properties of the graphene hyperlens. An example of magnification of two point sources separated by λ/5 to the size of few wavelength, which then can be detected with conventional optics, at frequency f = 6 THz (λ=50 μm) is shown in the Fig. 1. The details of the graphene hyperlens design as well as the dispersion diagram calculation method will be provided during the presentation

Wave Propagation Retrieval Method For Metamaterials: Unambiguous Restoration Of Effective Parameters

In this article we propose a new direct method of effective parameters restoration that is based on the wave propagation phenomenon. It retrieves the effective properties unambiguously, is applicable to thick metamaterial (MTM) slabs and is easy in implementation. It is validated on the case studies of fishnet, split cube in carcass, Jerusalem cross and ultrahigh refractive index MTMs. The constraints of the method are designated.Comment: 14 pages, 10 figures, submitted to Physical Review

Nanocouplers for Infrared and Visible Light

An efficient and compact coupler—a device that matches a microwaveguide and a nanowaveguide—is an essential component for practical applications of nanophotonic systems. The number of coupling approaches has been rapidly increasing in the past ten years with the help of plasmonic structures and metamaterials. In this paper we overview recent as well as common solutions for nanocoupling. More specifically we consider the physical principles of operation of the devices based on a tapered waveguide section, a direct coupler, a lens, and a scatterer and support them with a number of examples

Homogenization of metasurfaces formed by random resonant particles in periodical lattices

In this paper we suggest a simple analytical method for description of electromagnetic properties of a geometrically regular two-dimensional subwavelength arrays (metasurfaces) formed by particles with randomly fluctuating polarizabilities. Such metasurfaces are of topical importance due to development of mass-scale bottom-up fabrication methods, for which fluctuations of the particles sizes, shapes, and/or composition are inevitable. Understanding and prediction of electromagnetic properties of such random metasurfaces is a challenge. We propose an analytical homogenization method applicable for normal wave incidence on particles arrays with dominating electric dipole responses and validate it with numerical point-dipole modeling using the supercell approach. We demonstrate that fluctuations of particles polarizabilities lead to increased diffuse scattering despite the subwavelength lattice constant of the array. The proposed method can be readily extended to oblique incidence and particles with both electric and magnetic dipole resonances.Comment: 10 pages, 5 figure