Unidirectional Operation of p-GaN Gate AlGaN/GaN Heterojunction FET Using Rectifying Drain Electrode.

In this study, we proposed a rectifying drain electrode that was embedded in a p-GaN gate AlGaN/GaN heterojunction field-effect transistor to achieve the unidirectional switching characteristics, without the need for a separate reverse blocking device or an additional process step. The rectifying drain electrode was implemented while using an embedded p-GaN gating electrode that was placed in front of the ohmic drain electrode. The embedded p-GaN gating electrode and the ohmic drain electrode are electrically shorted to each other. The concept was validated by technology computer aided design (TCAD) simulation along with an equivalent circuit, and the proposed device was demonstrated experimentally. The fabricated device exhibited the unidirectional characteristics successfully, with a threshold voltage of ~2 V, a maximum current density of ~100 mA/mm, and a forward drain turn-on voltage of ~2 V.

Successful Endovascular Stent-Graft Repair for Complicated Type B Aortic Dissection Developed in a Patient with Polycystic Kidney Disease.

Polycystic kidney disease (PCKD) is rarely associated with aortic dissection (AD), which is a life-threatening disease. Although endovascular stent-graft repair tends to show better outcomes than conventional therapies in complicated type B AD (TBAD), successful endovascular intervention of TBAD with malperfusion in a patient with PCKD has not been reported. This case shows a 37-year-old male who had sudden onset of sharply stabbing epigastric pain with severe hypertension, who was diagnosed with TBAD and PCKD by a computed tomography and initially underwent medical treatment. Four days after discharge, he was rehospitalized with left leg pain and paresthesia due to left lower leg malperfusion. Thoracic endovascular stent-graft repair covering the primary tear site of dissection was performed successfully, leading to a decrease in false lumen and improvement of symptoms. We report the case of complicated TBAD in a patient with PCKD treated with endovascular stent-graft repair.

Multi-band metamaterial absorber based on the arrangement of donut-type resonators.

We propose multi-band metamaterial absorbers at microwave frequencies. The design, the analysis, the fabrication, and the measurement of the absorbers working in multiple bands are presented. The numerical simulations and the experiments in the microwave anechoic chamber were performed. The metamaterial absorbers consist of an delicate arrangement of donut-shape resonators with different sizes and a metallic background plane, separated by a dielectric. The near-perfect absorptions of dual, triple and quad peaks are persistent with polarization independence, and the effect of angle of incidence for both TE and TM modes was also elucidated. It was also found that the multiple-reflection theory was not suitable for explaining the absorption mechanism of our investigated structures. The results of this study are promising for the practical applications.

Polarization-independent dual-band perfect absorber utilizing multiple magnetic resonances.

We propose a dual-band metamaterial perfect absorber at microwave frequencies. Using a planar metamaterial, which consists of periodic metallic donut-shape meta-atoms at the front separated from the metallic plane at the back by a dielectric layer, we demonstrate the multi-plasmonic high-frequency perfect absorptions induced by the third-harmonic as well as the fundamental magnetic resonances. The origin of the induced multi-plasmonic perfect absorption was elucidated. It was also found that the perfect absorptions at dual peaks are persistent with varying polarization.

Highly-dispersive transparency at optical frequencies in planar metamaterials based on two-bright-mode coupling.

Using a planar metamaterial, which consists of two silver strips, we theoretically demonstrate the plasmonic electromagnetically-induced transparency (EIT)-like spectral response at optical frequencies. The two silver strips serve as the bright modes, and are excited strongly by the incident wave. Based on the weak hybridization between the two bright modes, a highly-dispersive plasmonic EIT-like spectral response appears in our scheme. Moreover, the group index is higher than that of another scheme which utilizes the strong coupling between the bright and dark modes.

Active manipulation of plasmonic electromagnetically-induced transparency based on magnetic plasmon resonance.

Plasmonic electromagnetically-induced transparency (EIT) can be excited by a single optical field unlike EIT in atom system, since the coupling between the bright and the dark modes is inherently induced through the near-field interaction in metamaterials. As a result, the complexity of the experimental realization can be reduced significantly, while the tunability is lost inevitably.We suggest a scheme that the plasmonic EIT is possible to be actively manipulated even by the single optical field. The bright and the dark modes are selective to be either coupled or uncoupled, depending on the angle of incidence. Even though the mechanical control has the disadvantage for high-speed applications, it paves the way for active manipulation of plasmonic EIT and benefits the clarification of its origin.

Plasmonic electromagnetically-induced transparency in symmetric structures.

A broken symmetry is generally believed to be a prerequisite for plasmonic electromagnetically-induced transparency (EIT), since the asymmetry allows the excitation of the otherwise forbidden dark mode. Nevertheless, according to the picture of magnetic plasmon resonance (MPR)-mediated plasmonic EIT, we show that plasmonic EIT can be achieved even in symmetric structures based on the second-order MPR. This not only sharpens our understanding of the existing concept, but also provides a profound insight into the plasmonic coherent interference in the near-field zone.