Set Of Waveguide Modes Research Articles

A Single-Crystalline Silver Plasmonic Circuit for Visible Quantum Emitters.

Plasmonic waveguides are key elements in nanophotonic devices, serving as optical interconnects between nanoscale light sources and detectors. Multimode operation in plasmonic two-wire transmission lines promises important degrees of freedom for near-field manipulation and information encoding. However, highly confined plasmon propagation along gold nanostructures is typically limited to the near-infrared region due to ohmic losses, excluding all visible quantum emitters from plasmonic circuitry. We report on the top-down fabrication of complex plasmonic nanostructures in single-crystalline silver plates. We demonstrate the controlled remote excitation of a small ensemble of fluorophores by a set of waveguide modes and the emission of the visible luminescence into the waveguide with high efficiency. This approach opens up the study of a nanoscale light-matter interaction between complex plasmonic waveguides and a large variety of quantum emitters available in the visible spectral range.

A hybrid mode-matching finite-elements approach to the analysis of thick dichroic screens with arbitrarily shaped apertures

A hybrid mode-matching (MM) finite-elements (FE) technique for the rigorous analysis of thick-screen inductive frequency selective surfaces (FSSs) is presented. The proposed hybrid approach combines the computational efficiency of the MM analysis with the versatility and flexibility of the FE method, enabling us to accurately model the electromagnetic behavior of inductive dichroic screens. These latter are realized by periodically perforating thick metallic screens with arbitrarily shaped apertures. The electromagnetic fields in the free-space region are expanded through a complete set of Floquet modes allowing us to reduce the analysis to the single periodicity cell; a set of waveguide modes is used inside the openings, each mode is numerically determined through an FE method procedure that relies on edge elements. A spectral criterion to determine the correct ratio between the number of waveguide and Floquet modes is adopted. Samples of numerical results are shown in order to check both the effectiveness and the accuracy of the proposed procedure.

Expansion of an arbitrary field in terms of waveguide modes

The problem of expanding a field over the set of waveguide modes is well known. Nevertheless, one may find small differences in the way this concept is used. Some employ a superposition of waveguide modes that include all field components, and a mode is considered as a single entity which propagates undisturbed along the structure. Others prefer to expand only the transverse-field components, whereas the longitudinal ones are derived from Maxwell's equations. It is shown that the latter is correct, at least for the important class of 2-dimensional structures. The two approaches coincide, however, if the structure is the waveguide for which the set of modes was calculated. The formal mathematical proof is restricted to a nonlossy medium. It is shown that the modes with real propagation coefficients squared suffice to construct a complete set. Depending on the boundary conditions in the longitudinal z direction, some or many of these modes may or may not be needed.

The interpolation of general active array impedance from multielement simulators

The multielement waveguide simulator gives the active reflection coefficient of an infinite array at a discrete number of scan angles. A general method to estimate the active reflection coefficient at in between angles is presented. The method expands any array excitation into a series using the orthogonal set of waveguide modes of the simulator. The portion of the simulator reflections which is proportional to the applied excitation is extracted. An estimate of the accuracy of the interpolation is also derived in terms of the form of the power reflected from the simulator. The technique is demonstrated on a 30- element simulator and comparisons are made with calculations for an infinite array composed of open-ended circular waveguides.