We calculated propagation constants of supermodes for two-dimensional two-slab waveguides, with small core gap, using second-order perturbation expansion from gapless slab waveguide system, and compared our results with the existing works. In the perturbation calculation, we used trapezoidal method to calculate the integral over the transverse direction in space and obtained second-order expansion of (core gap)/(core width) for propagation constants. Our result can explain the qualitative relationship between the propagation constants and the gap distance in the neighbor of (core gap)/(core width) being zero.

In the electromagnetic theory, the vacuum impedance Z0 is a universal constant, which is as important as the velocity of light c0 in vacuum. Unfortunately, however, its significance is not appreciated so well and sometimes the presence itself is ignored. It is partly because in the Gaussian system of units, which has widely been used for long time, Z0 is a dimensionless constant and of unit magnitude. In this paper, we clarify that Z0 is a fundamental parameter in electromagnetism and plays major roles in the following scenes: reorganizing the structure of the electromagnetic formula in reference to the relativity; renormalizing the quantities toward natural unit systems starting from the SI unit system; and defining the magnitudes of electromagnetic units.

Precise interconnect analysis is strongly required for giga-scale integration the operation frequency of which is excess 10 GHz. In this study, detailed and accurate analyses of a coaxial interconnect and an actual rectangular interconnect have been performed by the direct evaluation of Maxwell's equations and the finite element method, respectively. It has been revealed that there are two propagation modes for LSI interconnects: skin depth limited propagation mode and interconnect induced slow wave mode. In a miniaturized interconnect, the propagation mode is the interconnect induced slow wave mode; therefore, we cannot obtain the light-speed propagation due to such an interconnect-induced effect. In order to overcome this speed limitation or to improve signal integrity, it is essential to introduce a short interconnect for a miniaturized structure, and a much larger interconnect than the skin depth. We propose a gas-isolated interconnect as a candidate for an ultimately low-k structure in order to increase the signal-propagation speed. By the introduction of such structures, the performance of miniaturized devices in the deep submicron region will be effectively enhanced.

This paper presents a novel concept of a Two-Dimensional (2-D) Finite-Difference Time-Domain (FDTD) formulation for the numerical analysis of electromagnetic fields. FDTD method proposed by Yee is widely used for such analysis, although it has an inherent problem that there exist half-cell-length and half-time-step distances between electric and magnetic field components. To dissolve such distances, we begin with the finite-difference approximation of the wave equation, not Maxwell's equations. Employing several approximation techniques, we develop a novel algorithm which can condense all field components to equidistant discrete nodes. The proposed algorithm is evaluated in comparison with several conventional algorithms by computer simulations.