Dispersion measurements are described for slot lines constructed on alumina substrates, covering the 26-37 GHz frequency range. Wavelength ratios of slot lines were calculated from the measured resonant frequencies of slot ring resonators. Their advantages are that no end effects need to be considered. The experimental results are compared with the computed values through the hybrid-mode analysis in the spectral domain. Furthermore, the effect of shielding walls, which is important in practical design, was investigated.

This paper presents a hybrid-mode analysis for computing the resonant frequencies of a shielded coupled microstrip resonator. This analysis is based upon Galerkin's method in the Fourier transform domain. The computed resonant frequencies of even and odd modes agree will with the measured values for alumina substrates. Furthermore, a variety of numerical data for resonant frequencies are shown.

A shielded velocity-matched Ti:LiNbO3 optical modulator with a ridge is investigated. The analytical method is based on the second-order triangular element finite element method. The thickness of the coplanar waveguide traveling-wave electrode is taken into consideration and the relationship between the electrode thickness and optimum overlaid layer thickness is clarified. Incorporating a ridge into these Ti:LiNbO3 optical modulators can improve not only their modulation bandwidth but also their driving voltage.

We studied three types of lasers emitting narrow beam divergence of output light: 1) a spot-size converter integrated laser diodes (SS-LDs) with a vertically tapered waveguide, 2) one with a laterally tapered waveguide, and 3) one consisting of a small cross section of active region. We compared them with regard to their performance in coupling efficiency to a cleaved single mode fiber, threshold current, output power, and reliability. Both the spot-size converted integrated lasers with vertically and laterally tapered waveguide repeatedly provided low threshold currents of as low as 6 mA and low coupling loss to the fiber of 1.2 to 2.5 dB in two inch wafer processes. As a result of the aging test, the SS-lasers were predicted to have the same degradation rate as a conventional buried heterostructure laser. The laser having a small cross section of active layer also has low coupling loss and high efficiency up to 85.

This paper reviews Ti:LiNbO3 and semiconductor optical waveguide modulators. The operating principle of the Ti:LiNbO3 optical waveguide modulator is based on the Pockels effect. On the other hand, semiconductor optical modulators can be operated based on the Pockels effect, the Franz-Keldysh effect, or the quantum confined stark effect (QCSE) by employing multiple quantum wells (MQWs). Ti:LiNbO3 optical waveguide modulators are discussed with emphasis on the velocity-matching and optical waveguides. MQW optical waveguide modulators are discussed in view-point of design of a MQW structure, waveguide and modulation bandwidth.

We show the design of the bandwidth and the external quantum efficiency (including the coupling efficency to a single-mode fiber) of p-i-n photodetectors. Based on their design procedures, the performance limits of both conventional surface-illuminated photodetectors and side-illuminated photodetectors are evaluated. We point out that in the ultrawide-band region, optical waveguide photodetectors have great advantages over conventional surface-illuminated photodetectors in terms of the product of the bandwidth and the external quantum efficiency. It is shown that a 100-GHz bandwidth can be achieved with little degradation of the external quantum efficiency by a multimode waveguide photodetector structure. We also present a design concept for overcoming the performance limits of solitary waveguide photodetectors by including an input tapered optical waveguide.

A full-wave analysis is presented for computing resonant frequencies and the end effect of slot resonators. The formulation is based upon the spectral domain approach, which was first suggested by Itoh and Mittra. The Fourier transformed admittance Green functions are analytically derived to save computer time. The characteristic equation is obtained by Galerkin's procedure in the Fourier transform domain. It is confirmed that the sensitivity of the solutions to the basis functions is small using different basis functions. The resonant frequencies are shown for different structual parameters. The numerical results of the end effect are in good agreement with the experimental results published by other investigators. This analysis can be applied to the design of microwave integrated circuits used the shorted-slot lines, such as microstrip-slot transitions or slot filters.