Guy A. E. Vandenbosch

Plasmon Line Shaping Using Nanocrosses for High Sensitivity Localized Surface Plasmon Resonance Sensing

The detection of small changes in the wavelength position of localized surface plasmon resonances in metal nanostructures has been used successfully in applications such as label-free detection of biomarkers. Practical implementations, however, often suffer from the large spectral width of the plasmon resonances induced by large radiative damping in the metal nanocavities. By means of a tailored design and using a reproducible nanofabrication process, high quality planar gold plasmonic nanocavities are fabricated with strongly reduced radiative damping. Moreover, additional substrate etching results in a large enhancement of the sensing volume and a subsequent increase of the sensitivity. Coherent coupling of bright and dark plasmon modes in a nanocross and nanobar is used to generate high quality factor subradiant Fano resonances. Experimental sensitivities for these modes exceeding 1000 nm/RIU with a Figure of Merit reaching 5 are demonstrated in microfluidic ensemble spectroscopy.

Experimental Realization of Subradiant, Superradiant, and Fano Resonances in Ring/Disk Plasmonic Nanocavities

Subradiant and superradiant plasmon modes in concentric ring/disk nanocavities are experimentally observed. The subradiance is obtained through an overall reduction of the total dipole moment of the hybridized mode due to antisymmetric coupling of the dipole moments of the parent plasmons. Multiple Fano resonances appear within the superradiant continuum when structural symmetry is broken via a nanometric displacement of the disk, due to coupling with higher order ring modes. Both subradiant modes and Fano resonances exhibit substantial reductions in line width compared to the parent plasmon resonances, opening up possibilities in optical and near IR sensing via plasmon line shape design.

Reactive Energies, Impedance, and

New expressions are derived to calculate the reactive energy stored in the electromagnetic field surrounding an electromagnetic device. The resulting expressions are very simple to interpret, completely general, explicit and without approximations in terms of the currents flowing on the device. They are also fast since they involve integrals solely over the device generating the field. The new technique is very feasible to be used in cases where the electric and magnetic reactive energies are important in practice, especially in the case of radiating structures. Used there, they allow to study the effect of the shape of the device on the amount of reactive energy, and thus on the Q of the device. The implementation of the new expressions in numerical CAD tools is extremely simple and straightforward.

{\rm Q}

A new broadband textile based PIFA antenna structure designed for wireless body area network (WBAN) applications is presented. The new topology can be directly integrated into clothing. The study starts by considering three different materials: flexible copper foil, and ShieldIt Super and pure copper polyester taffeta conductive textiles. Bandwidth broadening is successfully achieved by implementing a novel and simple slot in the radiating patch. The measured reflection coefficient and radiation characteristics agree well with simulations. Moreover, radiation characteristics and bandwidth show satisfactory immunity against detuning when operating on-body, especially when placed on the back. To our knowledge, the proposed structure is the first fully fabric based slotted PIFA to be reported in open literature with high bandwidth (more than 46%) and reasonable gain (ca. 1.5 dB), to be used for multiple applications in the frequency band of 1.8 to 3.0 GHz.

Factor of Radiating Structures

The well-known procedure for determining the electric field in a structure consisting of an arbitrary number of planar dielectric layers is modified in order to obtain a form specially suited for the analysis of multiprobe multipath configurations. In general, the field is generated by arbitrary currents in the layers and arbitrary sheet currents in the transitions between the layers. The currents may be electric as well as magnetic, and the dielectric layers are isotropic, homogeneous, and lossy. The procedure results in Greens functions especially suited for the analysis of multiprobe multipatch configurations. They can be used in an efficient mixed-potential integral expression formulation. The theoretical procedure is applied in the case of a probe current source situated in one of the dielectric layers of the structure. For this probe current a highly efficient attachment current distribution is derived. Comparison of measured and calculated results for example structures proves the accuracy of both the approach and the attachment mode. >

Design of a Broadband All-Textile Slotted PIFA

The moment method is used to solve the integral equations describing the capacitively fed rectangular microstrip antenna element. This element consists of a ground plane, a radiating patch, and a small patch located between ground plane and radiating patch. The small patch is fed by a coaxial probe. It excites the radiating patch through capacitive coupling. After checking the accuracy by comparing calculated and measured results, the effect of the capacitor patch is analyzed theoretically. A procedure is given to determine capacitor patches which yield elements matched to the coaxial feed. It is shown how a matched configuration can be found for a given capacitor patch height. >

Mixed-potential integral expression formulation of the electric field in a stratified dielectric medium-application to the case of a probe current source

A fully textile microstrip topology with ultra wideband (UWB) characteristics useful in wireless body area networks (WBAN) is proposed. The antenna is operable within the full UWB band and incorporates a full textile shielding ground plane. The full ground plane is shown to be crucial in maintaining the performance when worn on-body. It successfully reduces any on-body performance degradation, resulting in a very robust structure. A detailed numerical and experimental evaluation of the antenna is performed in free space and on body.

Study of the capacitively fed microstrip antenna element

In this letter, a novel antenna topology based on the printed tapered monopole antenna (PTMA) is investigated in view of ultra-wideband (UWB) wireless body area network (WBAN) applications. First, the bandwidth in the presence of a human arm is studied. Second, the pulse distortion of a modulated Gaussian pulse is investigated, based on measured S21-parameters. We observe that there is a small acceptable influence on the matching of the antenna and that the pulse distortion is low. The main conclusion is that this modified PTMA is a very good candidate for WBAN UWB applications

UWB All-Textile Antenna With Full Ground Plane for Off-Body WBAN Communications

A compact circular polarizer is presented, which is based on a twisted double split-ring resonator (DSRR). The bottom DSRR is rotated 90° with respect to the top one. When the structure is illuminated by a normally incident linearly polarized wave, the two linear components of the transmitted wave have nearly equal amplitudes and 90° (−90°) phase difference around the resonant frequency. This means that the transmitted wave with left-handed circular polarization is much larger (smaller) than the one with right-handed circular polarization. The electric fields and currents on the structure are analyzed to illustrate this phenomenon. The size of each unit cell in this structure is extremely small compared with the wavelength in all three dimensions. Both simulations and measurements verify our design at microwave frequencies.

A Novel Small-Size Printed Tapered Monopole Antenna for UWB WBAN

The moment method is used to determine the radiation and impedance properties of microstrip patch antennas in multilayered material configurations. The resonance conditions for the layer structure which allow for high gain are studied. The gain, the impedance, the beamwidth, and the bandwidth are discussed. >