Circuit model analysis extensively used to describe metamaterials response at radio and microwave frequencies needs
significant revision for application to metallic resonators in the infrared frequency range. A self consistent filament
current based approach is elaborated providing parameter values accurately describing resonators internal properties as well as inter-resonator couplings. The model is verified by comparing the excitations in a five element array obtained
from the numerical simulation using CST MWS solver with the predictions provided by the model. Although the results
presented here concern with loop like magnetic resonators, the model can also be extended to other resonator shapes, for example metallic rods.
The transformation of 2-dimensional slab photonic crystal into 2-dimensional photonic glass was achieved by
gradually increasing the sphere spacing and by randomising the lattice. The materials were prepared by assembling
colloidal particles at the air/water interface using a Langmuir-Blodgett trough and the subsequent deposition on glass
substrates. Highly ordered monolayers were obtained by using colloids of one size, while use particles of two
different sizes and different partial concentrations allows to increase the spacing of the larger spheres and to
randomize the lattice. Changes in the spheres arrangements result in a change of in-plane light propagation from
band-like to hopping photon transport.
Properties of split-ring metamaterials are governed by inter-element interactions. These interactions lead to slow
eigenmodes of coupling, which, due to their short wavelengths, are ideal candidates for the design of near-field
manipulating devices. In this paper we explore the electric and magnetic coupling mechanisms in nano-U and nano-SRR
dimers comprising of two identical nano-resonators arranged axially and twisted relative to each other by an arbitrary
angle. We study theoretically the couplings in a periodic chain of nano-dimers for the frequencies from 100 to 300 THz.
In our analytical model, the electric and magnetic couplings can be expressed through the self and mutual terms for the
magnetic and electric field energy. In addition, we incorporate the effect of kinetic inductance due to the inertia of the
electrons (noticeable as element dimensions approach 100nm or smaller). The resulting dependence of the electric,
magnetic and the total coupling constants on the twist angle within the dimer obtained analytically is shown to agree
with numerical simulations (CST Microwave Studio). Our approach should enable an effective design of metamaterial
structures with desired properties and would be a useful tool in developing THz range manipulating devices based on
propagation of slow waves by virtue of coupling.
The dispersion equation of a magneto-inductive wave along a line of magnetically coupled resonant elements is investigated under conditions when retardation must be taken into account. It is shown that both the radiation resistance and the imaginary part of the mutual inductance appear in the modified dispersion equation which allows interaction up to the <i>p</i><sup>th</sup> neighbour. The problems arising in the solution of the full dispersion equation are discussed and it is concluded that the general solution leading to a large number of high-attenuation branches may not lead to a solution that is easily interpretable physically. It is suggested that the dispersion equation is to be derived from the variation of the current along an array of a finite number of elements excited by a voltage applied to the first element. The solution is obtained for a planar array of capacitively loaded loops in a closed form by inverting the complex mutual inductance matrix. It is shown that retardation and higher order interactions have greater effect upon the attenuation of the arising backward wave than upon the phase change per element. The appearance of a forward wave with a phase velocity close to that of light is also shown.
We describe subwavelength properties of magnetic metamaterials designed to manipulate and control the near field by employing magnetoinductive (MI) waves. MI waves owe their existence to the magnetic coupling between metamaterial elements. Magnetic field distributions and Poynting vector streamlines are used to visualise the diamagnetic and paramagnetic properties of metamaterials and to analyse working principles of MI waveguides and MI waveguide components.
One-dimensional lines of metamaterial elements supporting magneto-inductive waves are investigated for the case when elements' properties vary in a doubly periodic manner. It is shown that the dispersion of the magneto-inductive waves in this case demonstrates (analogously to acoustic waves in solids) an "optical" and an "acoustic" branch. The properties of the dispersion relation are investigated with attention paid to the width of pass- and stop-bands and the possibility of tailoring the dispersion properties within this approach is discussed.
We report on a hybrid integrated metro ring node subsystem on a chip that consists of an array of four independent reconfigurable optical add-drop circuits, each with power monitoring and automatic load balancing, and supporting shared and dedicated protection protocols in two-fiber metro ring optical networks. The four-channel metro ring node chip has polymeric optical waveguiding circuitry, thermally actuated with heaters consisting of resistive strips of metal. Photodiode arrays are flip-chip mounted on top of 45° mirrors cut in the waveguides of optical power taps. The mirrors are fabricated by Excimer laser ablation of the polymer followed by smoothing and metalization. The non-integrated implementation of a metro ring node uses 48 discrete elements, namely 8 1×2 switches, 8 2×2 switches, 8 VOAs, 12 taps, and 12 photodiodes. The proposed integrated solution is an exemplary embodiment of the benefits of optoelectronic integration as it provides, when compared to the discrete solution, significant cost reduction, space savings, lower electrical power consumption, higher reliability (fewer devices, runs cooler), and fewer board-level fiber interconnects.
One of the principal tasks of numerically simulating integrated optical devices is the accurate calculation of modal fields and propagation constants. Our recently proposed 'wave-matching-method' for dielectric waveguides with rectangular and piecewise constant refractive index profiles is based on expansions of the electromagnetic field into functions with harmonic and exponential dependence on the transverse coordinates. Local expansions for regions with constant permittivity are joined by minimizing a least squares expression for the remaining misfit at the discontinuity lines. For this paper the wave-matching analysis has been applied to a number of more complex structures: a conventional, deeply etched two-waveguide coupler, an ARROW- waveguide, a three dimensional four-waveguide coupler and three-waveguide coupler with multimode central rib (radiatively coupled waveguides). We have found good overall agreement where a direct comparison with published results is possible.
Shifting the location of a dielectric boundary in the cross section of an integrated optical waveguide with piecewise constant refractive index profile results in a permittivity perturbation in a layer along the discontinuity line. On the basis of these thin layer perturbations, we discuss perturbational expressions for the derivatives of the propagation constants with respect to geometry parameters, both for fully vectorial, hybrid and for semivectorial approximations to the basic mode fields. The expressions are numerically verified by comparison with rigorously calculated data for a common semiconductor rib waveguide. Applied to a more complex device, the perturbational approach allows to estimate its complete set of tolerances for the geometry parameters including the wavelength, on the basis of a single mode analysis. This is exemplified with a two rib waveguide coupler. By comparison with conventionally computed tolerances we give some assessment for the applicability of the effective perturbational approach.