A novel energy relation in eigen modes of transmission line is herein proposed and the variational expressions for propagation constant of various transmission lines can be systematically derived through this relation.

This paper attempts a complete analysis of circulator in reference to "circuit-invariance" in order to arrive at an invariant of and a canonical representation for circulator. Furthermore, a suitable figure of merit of circulator can be initially derive by means of this invariant, and a compensating circuit for circulator is discussed in as thorough a manner as possible.

In integrated optics, it is very important to provide efficient optical coupling between fibers and waveguide devices. In this letter, we propose a fiber-waveguide coupler, whose guide width varies in propagation direction, and show its better coupling behavior than an uniform coupler.

A simple and practically accurate method for studying rectangular dielectric waveguides is proposed. This method can provide good evaluations of propagation constant and field distribution of the waveguides by analyzing improved equivalent guide models. In this paper, it is applied in studying a novel taper-formed waveguides system. The waveguides system was experimentally demonstrated of being advantageous in its lightwave transmission characteristics. Experimentally obtained results exhibited good agreement with the performances predicted by the system numerical analyses using the proposed waveguide study technique.

Design of a waveguide-type optical isolator using the Faraday and Cotton-Mouton effects for nonreciprocal and reciprocal mode conversions, respectively, is presented. A noteworthy conclusion is obtained that, comparing with the previous design using a phase-matched waveguide, the device length is reduced by allowing phase-mismatch between TE and TM modes in the waveguide.

A novel nonlinear directional coupler consisting of tapered and uniform waveguides with self-focusing or self-defocusing nonlinear material is proposed to improve all-optical switching characteristics. Its switching characteristics are analyzed by using a beam propagation method based on the Galerkin's finite element technique (FE-BPM), in which nonuniform sampling spacings along the transverse coordinate are adopted. It is presented that the tapered nonlinear directional coupler shows fairly distinct 'high' and 'low' states of output power with steep transition versus input power. This property is discussed in comparison with conventional nonlinear directional couplers consisting of uniform symmetric and uniform asymmetric coupled waveguides. In addition, the effects of loss on the characteristics of tapered nonlinear directional coupler are examined.

The optical absorption loss of Ca doped LPE grown rare earth iron garnet films can be reduced by the reducing treatment. The absorption loss is greatly affected by Ar sputter-etching whereas it is shown that the reducing treatment after O2 sputter-etching is suitable for making low-loss waveguides.

A microfabrication technique using a sputter-etching with Ar, including the process of a mask formation, is described. A Ti etch resistant mask was formed by using a lift-off technique following an electron beam exposure lithography. The sputter-etch rate of YIG, Ta2O5, Ti and Al were determined. Grating patterns with fairly deep grooves were fabricated on YIG and Ta2O5 successfully.

A new type of edge-guided mode (E. G. Mode) isolator is proposed, which has the following desirable characteristics: (a) high isolation (more than 40 dB with 1dB insertion loss), (b) simple structure without additional lossy materials, and (c) considerably broad band (40% relative bandwidth). Moreover, a new type of E. G. mode circulator for which the scattering matrix is of the non-cyclic from is also proposed.

By combining rubber with carbon and ferrite in an appropriate weight ratio, the material which has both dielectric and magnetic losses, suitable for an electromagnetic-wave absorber, is obtained. The dispersion characteristics of complex relative permittivity and permeability of this material are measured, and equations of both permittivity and permeability are derived in RF frequencies. By using these dispersion equations, we can easily simulate applications using this kind of material as an electromagnetic wave absorvber.

A novel series-tapered nonlinear directional coupler is proposed to improve all-optical switching characteristics. Its switching characteristics are analyzed by using a beam propagation method based on the Galerkin's finite element technique. It is presented that the critical power of the series-tapered nonlinear directional coupler is smaller than conventional uniform symmetric and tapered nonlinear directional couplers.

In this short note, an upper limit of modulation enhancement of electronic phase shifter employing a multilayer dielectric-waveguide structure is provided by the application of general theory of dielectric waveguides.

The single layer absorber has the simplest structure among electromagnetic wave absorbers. To have thin and light materials with wide frequency characteristics for this structure, carbon and ferrite are mixed with rubber in different weight ratios. This new material has both dielectric and magnetic losses, which in a single layer structure, has good absorber characteristics . In the C-band, the relative bandwidth is up to 4.6 times wider, and the absorber is thinner, compared with nonmagnetic lossy dielectric material (i.e., 1.0, 0).

A modified beam propagation method based on the Galerkin's technique (FE-BPM) has been implemented and applied to the analysis of optical beam propagation in a tapered dielectric waveguide. It is based on a new calculation procedure using non-uniform sampling spacings along the transverse coordinate. Comparison with a conventional FE-BPM shows a definite improvement in saving computation time. The differences of a propagation field and a mean square power given by the proposed FE-BPM are discussed in comparison with the conventional FE-BPM.

The shielding effect of a new material composed of rubber with carbon and ferrite for microwave oven leakage is investigated. By adding an appropriate amount of carbon, the shielding effect is improved. A large attenuation constant, which is 6 dB/cm larger than that of a rubber ferrite, is relizable.