Non-ideal cloaking based on Fabry-Perot resonances in single-layer high-index dielectric shells

Cataloged from PDF version of article.Strong reduction of the scattering cross section is obtained for subwavelength dielectric and conducting cylinders without any magnetism for both TE and TM polarizations. The suggested approach is based on the use of Fabry-Perot type radial resonances, which can appear in single-layer, high-ε, isotropic, and homogeneous shells with the properly chosen parameters. Frequencies of the minima of the scattering cross section, which are associated with the cloaking, typically depend on whether TE or TM polarization is considered. In some cases, large-positive-ε and largenegative-e objects can be cloaked. In other cases, non-ideal multifrequency cloaking can be realized. ©2009 Optical Society of America

Spatial and spatial-frequency filtering using one-dimensional graded-index lattices with defects

Cataloged from PDF version of article.The potential of one-dimensional, periodic, graded-index, isotropic dielectric lattices with defects in multiband spatial and spatial-frequency filtering is studied. It is shown that both narrow- and wide-bandpass filters can be obtained at a proper choice of the number, location, and parameters of the defects placed inside the relatively thin slabs. The peculiarities of achieving multibandness for narrow- and wide-bandpass filters are discussed. Multiband narrow-bandpass filtering is closely related to the transmission features that are associated with Fabry-Perot resonators with semitransparent planar mirrors. Correspondingly, the observed transmission can be interpreted in terms of the equivalent parameters of such resonators. In particular, it is shown that the resonators filled with an ultralow-index medium can be mimicked, so that defect-mode angle-domain spectrum can be rarefied at large angles of incidence. The obtained results are also expected to be applicable for prediction of the angle-domain behavior of transmission in case of piecewise-homogeneous multilayers. (C) 2009 Elsevier B.V. All rights reserved

Polarization tunable all-dielectric color filters based on cross-shaped Si nanoantennas

Polarization sensitive and insensitive color filters have important applications in the area of nano-spectroscopy and CCD imaging applications. Metallic nanostructures provide an efficient way to design and engineer ultrathin color filters. These nanostructures have capability to split the white light into fundamental colors and enable color filters with ultrahigh resolution but their efficiency can be restricted due to high losses in metals especially at the visible wavelengths. In this work, we demonstrate all-dielectric color filters based on Si nanoantennas, which are sensitive to incident-wave polarization and, thus, tunable with the aid of polarization angle variation. Two different information can be encoded in two different polarization states in one nanostructure. The nanoantenna based pixels are highly efficient and can provide high quality of colors, in particular, due to low losses in Si at optical frequencies. We experimentally demonstrate that a variety of colors can be achieved by changing the physical size of the nonsymmetric cross-shaped nanoantennas. The proposed devices allow to cover an extended gamut of colors on CIE-1931 chromaticity diagram owing to the existence of high-quality resonances in Si nanoantennas. Significant tunability of the suggested color filters can be achieved by varying polarization angle in both transmission and reflection mode. Additional tunability can be obtained by switching between transmission and reflection modes

Principles for reducing the phase shift between instantaneous analogue and discrete signals and the corresponding values in the sampled values (SV) stream of a digital substation

There are numerous publicly available articles on digital substations, including those dedicated to current and voltage measurements, time synchronization, test systems development, principles of substation design, and other aspects of this topic. But the phase shift between instantaneous signals and the corresponding values in the SV (sampled values) stream has been little discussed. We can list the following principles to reduce the phase shift between instantaneous analogue and discrete signals and the corresponding values in the SV stream. 1) Exclusion from the device, of non-essential elements that introduce additional propagation delays of analogue and discrete signals, provided that such exclusion does not adversely affect the device performance or characteristics. 2) Reduction of the delay time for the other device elements to the minimum values. 3) Adjustment of the delay time of some device elements or addition of special delay elements to equalize the time of signal propagation over analogue and discrete channels. 4) Consideration of the total delay time of signal propagation over analogue and discrete channels and adjustment of the time stamp in the SV frame. The article provides examples of application of these principles in signal generation and measuring devices and phase shift meters