This article presents the design of a dielectric lens antenna that utilizes the concept of a stepped Fresnel lens for focusing electromagnetic millimeter waves. Based on the quasi-optical properties of these waves, a Cartesian Oval is optimized and employed as a focusing lens. Multiple such lenses are combined to two different Fresnel-based lens antennas. We survey these newly designed lens antennas and compare them with a focusing lens antenna based on a Cartesian oval and a far-field lens antenna. Simulations and measurements with a frequency-modulated continuous-wave (FMCW) radar validate the effectiveness of the new design, demonstrating an even improved focus size while significantly reducing the size and weight of the lens antenna by up to 53% and by nearly 48 %, respectively. Additionally, the Fresnel-based lens antennas reveal a frequency dependency, enabling frequency-based steering of the focal length over a wide relative tuning range of 177%, which we thoroughly investigate for various bandwidths and center frequencies.

In this paper, we present a near-field microwave microscopy method for the characterization of dielectric materials samples in the Industrial, Scientific and Medical (ISM) band. The system proposed is composed of a probe coupled to a dielectric resonator (DR) operating in the TE011 mode. Latter this is used to fix the resonance frequency of the resonator at 2.45 GHz. This system is used for the characterization of dielectric samples with accuracy and high spatial resolution, knowing that they do not have predetermined forms, but a small plane surface.The same device is used for a multi-frequency characterization (4–20 GHz) using resonance frequencies of the cavity instead of one resonance frequency of the DR.

In this paper, material selection has been done for dielectric substrate material in microstrip patch antenna (MPA) for three distinct classes of wireless communication applications using Ashby's approach. This material selection procedure is based on the creation and evaluation of Ashby's chart of different material indices. These material indices in turn affect the device performance indices, which decide the best possible dielectric material to be used as substrate for MPAs. In this work, quality factor, relative permittivity, and temperature coefficient of resonant frequency are chosen as material indices of MPA's dielectric substrate to get relevant performances. Ashby's selection chart shows that 0.75MgAl2O4–0.25TiO2 material for millimeter waves applications, Ca[(L1/3Nb2/3)0.85Ti0.15]O3−δ for mobile base station applications, and (Ba0.95Ca0.05)O–Sm2O3–4.5TiO2 ceramic for mobile phone miniaturization applications are the promising materials that allows best overall performance in MPAs for wireless communication.

Characteristic energies of photonic modes are a sensitive function of a nanostructures’ geometrical parameters. In the case of translationally invariant planar waveguides, the eigen-energies reside in the infrared to ultraviolet parts of the optical spectrum and they sensitively depend on the thickness of the waveguide. Using swift electrons and the inherent Cherenkov radiation in dielectrics, the energies of such photonic states can be effectively probed via monochromated electron energy-loss spectroscopy (EELS). Here, by exploiting the strong photonic signals in EELS with 200 keV electrons, we correlate the energies of waveguide peaks in the 0.5–3.5 eV range with planar thicknesses of the samples. This procedure enables us to measure the thicknesses of cross-sectional transmission electron microscopy samples over a 1–500 nm range and with best-case accuracies below ±2%. The measurements are absolute with the only requirement being the optical dielectric function of the material. Furthermore, we provide empirical formulation for rapid and direct thickness estimations for a 50–500 nm range. We demonstrate the methodology for two semiconducting materials, silicon and gallium arsenide, and discuss how it can be applied to other dielectrics that produce strong optical fingerprints in EELS. The asymptotic form of the loss function for two-dimensional materials is also discussed.

As a major improvement in three-dimensional (3D) atom probe, the range of applicable material classes has recently been broadened by the establishment of laser-assisted atom probes (LA-3DAP). Meanwhile, measurements of materials of low conductivity, such as dielectrics, ceramics, and semiconductors, have widely been demonstrated. However, besides different evaporation probabilities, heterogeneous dielectric properties are expected to give rise to additional artifacts in the 3D volume reconstruction on which the method is based. In this article, these conceivable artifacts are discussed based on a numeric simulation of the field evaporation. Sample tips of layer- or precipitate-type geometry are considered. It is demonstrated that dielectric materials tend to behave similarly to metals of reduced critical evaporation field.

Explosive growth in the fiber-optic telecommunications infrastructure during the past decade has driven noteworthy advances in thin-film-based optical interference filter technology. In particular, the widespread deployment of wavelength-division multiplexing (WDM), a means of increasing the communication capacity of an optical fiber by utilizing more than one wavelength of light, has motivated significant improvements in bandpass filter performance. A common requirement is for filters that combine or separate wavelengths spaced 100 GHz (0.8 nm) apart. The foundation for these recent breakthroughs has been laid by the development of optical coating technology over the past century. This article reviews the materials and processes used in the production of thin-film-based optical communications filters.