The coordinate transformation by using form-invariant transformations of Maxwell equations has led to an approach for designing devices with anisotropic metamaterial. In this paper, we present the design methodology for a low profile planar focusing antenna based on the transformation of a parabolic antenna. The electromagnetic behavior of the planar antenna is simulated by a two-dimensional finite element method and the results show that the planar antenna has the same performances as the parabolic antenna. The coordinate transformation technology provides an alternative design method to the conventional antennas.
We apply coordinate transformations in the design of waveguides with bent geometry to reduce reflection at the incident port. It was found that in the case of metallic waveguides, by applying the transformation to the medium inside a right-angle bent waveguide, low reflection can be obtained. For the case of dielectric waveguides, this can also be done by applying the same transformation to the bent region containing both the dielectric core and its claddings. Our proposed technique provides an alternative method for designing bent waveguides with low insertion loss.
Abstract-The propagation properties of surface plasmon polaritons (SPP) modes and surface magnetoplasmon polaritons (SMP) modes in a semiconductor slit waveguide are analyzed by the effective dielectric constant approach, and the interaction of the external magnetic field with the dispersion properties and field distributions of SMP modes in the Voigt configuration are emphasized in our analysis. Both the symmetric structure and the asymmetric structure are discussed in details. In contrast to the SPP modes which have one propagation band below the plasmon frequency only, the SMP modes have both the low-frequency propagation band below the plasmon frequency and the high-frequency propagation band above the plasmon frequency. When the external magnetic field increases, the two bands of the SMP modes will separate further in frequency, and the even symmetric distribution of the fundamental mode, which usually associates with the SPP mode, will be destroyed. These results can provide some guidance for the design of the tunable semiconductor waveguide in the terahertz regime.
Abstract-A detailed study of surface TM modes at the interface between an isotropic medium and a uniaxial plasma is presented. Four cases for the isotropic medium, including normal, Left-handed, magnetic, and metallic media, are considered. The conditions for the existence of surface modes in each case are analyzed, showing that the existence is determined by the parameters of media, working frequency, and the direction of the principle axis. The Poynting vector along the propagating direction is also calculated. Depending on the media parameters and the frequency, the surface mode can have time-average Poynting vector in the opposite direction of the mode phase velocity.
Abstract-The propagation properties of surface plasmon polaritons (SPP) modes in nanoscale narrow metallic structures: gap, channel, and rectangular-hole waveguides, are analyzed by the complex effective dielectric constant approximation. The results show that all the SPP modes exist below the critical frequency where the real part of metal permittivity is negative unity. It is found that both cutoff frequency and cutoff height exist in channel waveguide and rectangularhole waveguide. The channel and rectangular-hole waveguides have different propagation properties at cutoffs due to their different cutoff conditions. Compared with the gap waveguide, the channel waveguide has shorter propagation length and better confinement when the operation frequency is near the critical frequency, but has longer propagation length and worse confinement when the operation frequency is far from the critical frequency. Among the three waveguides, the rectangular-hole waveguide has the best confinement factor and the shortest propagation length. The comprehensive analysis for the gap, channel, and rectangular-hole waveguides can provide some guidelines in the design of subwavelength optical devices.
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