Experimental investigation of the effects of polarization on the measured radiation efficiency of a dielectric resonator antenna

©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.The radiation efficiencies of two rectangular dielectric resonant antennas (DRAs) were investigated using the directivity/ gain (D/G) method and the Wheeler cap method. Both antennas are linearly polarized but have different linear polarization purities. Through comparison of their radiation efficiencies, itpsilas shown that the polarization purity strongly affects the D/G measurement of the DRAspsila radiation efficiency.Qinghua Lai, Georgios Almpanis, Christophe Fumeaux, Hansruedi Benedickter, and Rüdiger Vahldiec

Acousto-optic interaction enhancement in dual photonic-phononic cavities

Light control through elastic waves is a well established and mature technology. The underlying mechanism is the scattering of light due to the dynamic modulation of the refractive index and the material interfaces caused by an elastic wave, the so-called acousto-optic interaction. This interaction can be enhanced in appropriately designed structures that simultaneously localize light and elastic waves in the same region of space and operate as dual optical-elastic cavities, often called phoxonic or optomechanical cavities. Typical examples of phoxonic cavities are multilayer films with a dielectric sandwiched between two Bragg mirrors or, in general, defects in macroscopically periodic structures that exhibit dual band gaps for light and elastic waves. In the present work we consider dielectric particles as phoxonic cavities and study the influence of elastic eigenmode vibrations on the optical Mie resonances. An important issue is the excitation of elastic waves in such submicron particles and, in this respect, we analyze the excitation of high-frequency vibrations following thermal expansion induced by the absorption of a femtosecond laser pulse. For spherical particles, homogeneous thermalization leads to excitation of the particle breathing modes. We report a thorough study of the acousto-optic interaction, correct to all orders in the acousto-optic coupling parameter, by means of rigorous full electrodynamic and elastodynamic calculations, in both time and frequency domains. Our results show that, under double elastic-optical resonance conditions, strong acousto-optic interaction takes place and results in large dynamical shifts of the high-Q optical Mie resonances, manifested through multiphonon exchange mechanisms

Benign Cystic Mesothelioma: A Rare Cause for Scrotal Swelling

Benign cystic mesothelioma of the tunica vaginalis is a rare occurrence. It usually presents with painless gradual swelling in the scrotum. These types of benign mesotheliomas typically occur in the peritoneum and usually affect young to middle-aged patients. We present in this case an unusual case of benign cystic mesothelioma of the tunica vaginalis in a 77-year-old male patient

Acousto-optic interaction enhancement in dual photonic-phononic cavities

Light control through elastic waves is a well established and mature technology. The underlying mechanism is the scattering of light due to the dynamic modulation of the refractive index and the material interfaces caused by an elastic wave, the so-called acousto-optic interaction. This interaction can be enhanced in appropriately designed structures that simultaneously localize light and elastic waves in the same region of space and operate as dual optical-elastic cavities, often called phoxonic or optomechanical cavities. Typical examples of phoxonic cavities are multilayer films with a dielectric sandwiched between two Bragg mirrors or, in general, defects in macroscopically periodic structures that exhibit dual band gaps for light and elastic waves. In the present work we consider dielectric particles as phoxonic cavities and study the influence of elastic eigenmode vibrations on the optical Mie resonances. An important issue is the excitation of elastic waves in such submicron particles and, in this respect, we analyze the excitation of high-frequency vibrations following thermal expansion induced by the absorption of a femtosecond laser pulse. For spherical particles, homogeneous thermalization leads to excitation of the particle breathing modes. We report a thorough study of the acousto-optic interaction, correct to all orders in the acousto-optic coupling parameter, by means of rigorous full electrodynamic and elastodynamic calculations, in both time and frequency domains. Our results show that, under double elastic-optical resonance conditions, strong acousto-optic interaction takes place and results in large dynamical shifts of the high-Q optical Mie resonances, manifested through multiphonon exchange mechanisms

Double-Bowtie-Slot-Coupled DRA for Enhanced Bandwidth

G. Almpanis, C. Fumeaux, V. Vahldiec

Dual-mode bridge-shaped dielectric resonator antennas

Different configurations of bridge-shaped dielectric resonator antennas (b-DRAs) made of high-permittivity materials are presented in this letter. These DRA geometries can be seen as an evolution of the notched rectangular DRAs introduced by other authors, but their operational principle is different. The particularities and advantages of the proposed geometry will be investigated and demonstrated for a single bridge first. Afterward, the concept will be extended to two realizations of well-operating dual-mode b-DRAs with stable radiation patterns and low cross polarization. For the analysis of these structures, a full-wave analysis solver (HFSS) was used. Prototype fabrication and measurements confirm the results of the simulations.Georgios Almpanis, Christophe Fumeaux and Rüdiger Vahldiec

Novel broadband dielectric resonator antennas fed through double-bowtie-slot excitation scheme

This paper discusses the concept and the realization of novel wideband dielectric resonator antennas (DRAs), in which a dielectric cylinder or parallelepiped are fed from a microstrip line through two parallel bowtie-slots. The concept of partial independence of the slot modes from the dielectric resonator mode is exploited in such a way that the resonances of the slot modes and of the DRA are designed to occur at different frequencies. As a result, the bandwidth of the DRA is significantly improved, while stability in the radiation patterns and low cross-polarization are maintained. Finally, a study is performed concerning the influence of the gap between the dielectric resonator and the ground plane upon the overall performance of the DRA. Comparison of the results from a commercial software tool (HFSS®) and from the Finite-Volume Time-Domain (FVTD) method is made. © 2007 ACES.G. Almpanis, C. Fumeaux and R. Vahldiec

Pyramidal dielectric resonator antennas for wideband applications

A coaxial-fed pyramidal dielectric resonator antenna (DRA) is studied theoretically and experimentally. Pyramidal dielectric resonator antennas are attractive candidates for many wireless applications, since they exhibit wide impedance bandwidth and stable radiation characteristics. Their operation relies on the excitation of multiple modes at nearby frequencies in order to obtain a wide operational bandwidth through the overlap of their resonances. The design concept is an evolution of the rectangular DRA; the pyramidal DRA offers however certain advantages such as more symmetrical radiation patterns and additional degrees of freedom for mode impedance-matching.G. Almpanis, C. Fumeaux and R. Vahldiec

Comparison of Various Non-Canonical Rectangular Dielectric Resonator Antennas for Enhanced Bandwidth

A probe-fed rectangular DRA is investigated and compared with two non-canonical structures, whose geometries can be seen as deviations from the parallelepiped. It is shown that these advanced geometries exhibit a larger impedance bandwidth than the canonical RDRA, while the rest of their properties are largely unchanged. In addition to that, the new structures do not require lengthy and complex fabrication procedures due to their relatively simple shape and feeding scheme. Finally, since these shapes are derivations from the rectangular geometry, similar modes are excited and hence their overall performance can be described and designed starting from the analytical expressions for the parallelepiped.G. Almpanis, C. Fumeaux and R. Vahldiec

Two-step rectangular dielectric resonator antenna

A coaxial-fed two-step rectangular dielectric resonator antenna (DRA) with wideband characteristics is studied theoretically and experimentally. The fundamental TE111 mode of the rectangular DRA features some attractive properties, such as a low radiation Q factor and broadside radiation patterns. In this paper, a two-step rectangular DRA is fed by means of a probe placed in direct contact with one facet of the structure. This results in the excitation of three modes with similar radiation characteristics. Therefore, tri-band or wideband operation can be achieved, if these modes are designed to resonate at nearby frequencies. Over 47% impedance bandwidth is obtained, while the polarization and the radiation patterns remain remarkably stable.G. AImpanis, C. Fumeaux and R Vahidieckhttp://www.eucap2006.org