A novel directional coupler utilizing a left-handed material

A novel directional coupler with a left-handed material (LHM) layer between two single-mode waveguides of usual material is introduced. The coupling system is analyzed with the supermode theory. It is shown that such a LHM layer of finite length can shorten significantly the coupling length for the two single-mode waveguides. A LHM layer with two slowly tapered ends is used to avoid the reflection loss at the ends.Comment: 3 pages, 2 figure

Identification of the major cause of endemically poor mobilities in SiC/SiO2 structures

Materials with good carrier mobilities are desired for device applications, but in real devices the mobilities are usually limited by the presence of interfaces and contacts. Mobility degradation at semiconductor-dielectric interfaces is generally attributed to defects at the interface or inside the dielectric, as is the case in Si/SiO2 structures, where processing does not introduce detrimental defects in the semiconductor. In the case of SiC/SiO2 structures, a decade of research focused on reducing or passivating interface and oxide defects, but the low mobilities have persisted. By invoking theoretical results and available experimental evidence, we show that thermal oxidation generates carbon di-interstitial defects inside the semiconductor substrate and that they are a major cause of the poor mobility in SiC/SiO2 structures