The modulation performance of traveling-wave type LiNbO3 guided-wave light modulators with coplanar waveguide structure is studied. The analysis shows that the use of a y-cut plate offers a low voltage modulation with decreased electrode separation although the characteristic impedance becomes low.

The tunable filter which utilize the collinear acoustooptic TE-TM mode conversion is discussed. A novel filter structure is proposed intended for realizing desired filter performances by the adjustment of waveguide parameters. Design examples are presented to confirm the advantage of this structure.

Traveling-wave light intensity modulator was constructed using the 5 µm wide strip optical waveguide of z-cut LiNbO3 and the asymmetric stripline as the modulator electrode. The half-wave voltage of 23 V and the extinction ratio of 97% were achieved. Modulation was performed up to 18 GHz.

The design practice of resonant electrodes is reported for guided-wave light modulators using coplanar waveguide electrodes. A matching stub built with the resonator provides compact structure and satisfactory electrical performance. It is notable that the wide-gap resonator electrode yields the decrease in driving power.

We propose novel all-optical functional devices using waveguide X-junctions with localized third order optical nonlinearity, where one branch is made from a Kerr-like nonlinear material and the rest are made from linear ones. All-optical switching operations can be obtained because of bistable like nonlinear dispersion characteristics in linear and nonlinear coupled guided-wave systems. The performances of the devices are analyzed by the Beam Propagation Method (BPM) modified for nonlinear waveguides combined with the nonlinear normal mode analysis. The methods to construct the waveguides with localized nonlinearity are also discussed by utilizing the technologies for the selective control of a band-gap energy of semiconductor Multi Quantum Well (MQW) structures and the performances of the designed devices are presented.

We propose novel all-optical functional devices using waveguide X-junctions with localized third order optical nonlinearity, where one branch is made from a Kerr-like nonlinear material and the rest are made from linear ones. All-optical switching operations can be obtained because of bistable like nonlinear dispersion characteristics in linear and nonlinear coupled guided-wave systems. The performances of the devices are analyzed by the Beam Propagation Method (BPM) modified for nonlinear waveguides combined with the nonlinear normal mode analysis. The methods to construct the waveguides with localized nonlinearity are also discussed by utilizing the technologies for the selective control of a band-gap energy of semiconductor Multi Quantum Well (MQW) structures and the performances of the designed devices are presented.

A filter-type coplanar parallel electrode with periodically loaded reactances is introduced to construct guided-wave light modulators of limited bandwidth. The device was built by using a Ti:LiNbO3 optical waveguide and was operated successfully at 633 nm. Measured 3 dB bandwidth was 1 GHz centered at 14.8 GHz. Required modulating power for 1 rad phase modulation was 67.6 mW.