The existence of trapped modes in coupled electromagnetic waveguides is experimentally investigated for configurations with different degrees of symmetry supporting hybrid modes. The occurrence of confined solutions in such open geometries is proven to be much more general than demonstrated so far, as predicted by Goldstone and Jaffe [J. Goldstone and R. L. Jaffe, Phys. Rev. B 45, 14100 (1992)]. The identification of the observed modes is based on the numerical modeling of the relative vector fields. The experimental results make evident that an increasing aperture of the configuration can improve the confinement of the mode instead of generating additional leakage channels. In particular, long-lived trapped modes can be easily obtained in geometries with a large aperture. Their resonance parameters can compete with those of standard close cavities working at millimeter wavelengths. The role of the symmetry on the properties of these trapped modes is discussed in detail.

This work is devoted to the study of the emitting properties of azimuthally inhomogeneous segmental dielectric resonators excited by whispering gallery modes. Due to the diffraction of the azimuthal waves on local nonhomogeneities located equidistantly along the azimuthal coordinate, intense electromagnetic radiation is achieved in the azimuthal sector of the angles 0°-360°. A prototype of an all-around emitting antenna based on basis of a segmental dielectric resonator is proposed, and its characteristics in the far zone are studied. It is shown that such an antenna forms a multilobe radiation pattern (72 lobes) in the circle sector of angles. The antenna gain in the lobes at the resonant frequency reaches 12 dB. Antenna optimization is achieved in the proposed method because of the large gain produced by the antenna. It is also analyzed that these types of radiation patterns observed by antennas are well used for the Internet of Things- (IoT-) based applications.

A probe head especially useful for electron paramagnetic resonance (EPR) spectrometers working at high field—high frequency is presented. The probe head is based on the whispering gallery mode dielectric resonators that proved very effective in the ultrahigh frequency range. The excitation network uses a properly shaped dielectric waveguide sharing its external field pattern with the field of the resonators. Very simple resonators made with polyethylene in both single and doubly stacked disk configurations are used. The experimental characterization by a submillimeter network analyzer shows for the resonances studied in a wide range of frequencies up to ≈400 GHz high loaded merit factor Q L values and good coupling factors. Resonators also maintain their general characteristics when large quantities of low loss samples for EPR measurements are properly inserted. Preliminary EPR spectra of diphenylpicrylhyldrazyl at 7 and 10 T obtained with the novel apparatus are finally presented.