Hiroshi Terui

Loss measurement and analysis of high-silica reflection bending optical waveguides

Bending loss of high-silica single-mode bending optical waveguides using a waveguide side-wall as a reflecting facet is described theoretically and experimentally as a function of the bending angle. Two types of bending waveguides, which have the reflecting facet exposed to the air coated with a metal film, are treated. The causes of bending loss are discussed in terms of los due to the Goos-Hanchen effect and the perpendicularity and roughness of the reflecting facet. >

Multichip optical hybrid integration technique with planar lightwave circuit platform

A two-step bonding technique for optical device assembly on a planar lightwave circuit platform was developed, which consists of a chip-by-chip thermo-compression prebonding step and a simultaneous reflow bonding step. The technique was used to realize multichip optical integration on the platform. The characteristics of the bonding technique were examined by investigating its strength and accuracy. The bonding accuracies in the horizontal and vertical directions were 1.1 and 0.8 /spl mu/m, respectively, with high bonding strength. The technique was first applied to a 3 chip integrated transceiver module and the 136 fabricated modules exhibited good performance. The average coupling loss between the laser diodes and the waveguide was estimated to be 4.1 dB and stable characteristics were observed during 1200 cycle thermal shock tests between -40 and 85/spl deg/C. Next, the two-step bonding technique was used for a 4 channel laser diode module on which 8 optical device chips were integrated and a low coupling loss was achieved of better than 4.2 dB which is as good as that of the 3 chip integrated optical modules.

Waveguide polarization-independent optical circulator

We fabricated a new type of waveguide polarization-independent optical circulator which does not need a polarization-beam splitter. The circulator is based on a non-reciprocal Mach-Zehnder interferometer which consists of two waveguide Faraday rotators, two thin-film half-waveplates and two planar lightwave circuit-type 3-dB couplers. The fabricated circulator provides a 14.0-23.7-dB isolation and a 3.0-3.3 dB insertion loss at /spl lambda/=1.55 /spl mu/m. This circulator presents a new possibility for developing non-reciprocal devices in the field of integrated optics.

A hybrid integrated waveguide isolator on a silica-based planar lightwave circuit

La and Ga substituted yttrium iron garnet single-mode buried channel waveguides, prepared using liquid-phase-epitaxial growth and Ar ion beam etching, have been successfully applied as 45/spl deg/ nonreciprocal waveguide rotators (NRWR) for hybrid integrated waveguide isolators at /spl lambda/=1.55 /spl mu/m. The optical and magneto-optical properties of the prepared 45/spl deg/ NRWRs and the epitaxial films are investigated in detail. We describe the assembly procedure and present optical measurement results for the hybrid integrated waveguide isolators. The hybrid isolators are composed of a 45/spl deg/ NRWR, a half-wave plate sheet, thin film-type polarizers, a thin plate-type permanent magnet and a silica-based waveguide on a silicon substrate. We obtained good waveguide isolators with low insertion losses ( 25 dB) in the 1.5 /spl mu/m wavelength band.

Hybrid integration of spot-size converted laser diode on planar lightwave circuit platform by passive alignment technique

An index alignment technique was developed for a planar lightwave circuit platform. The technique was successfully applied to the hybrid integration of a spot-size converted laser diode on the platform. The fabricated modules exhibited an average coupling loss of 4.2 dB and a maximum optical output power of 10 mW at an injection current of 70 mA.

Hybrid-integrated 4*4 optical gate matrix switch using silica-based optical waveguides and LD array chips

The fabrication and characteristics of a hybrid-integrated optical gate matrix switch were studied. The switch was composed of a silica-based single-mode guided-wave circuit and two InGaAsP gate array chips, each of which comprised eight laser diode optical gates. The gate array chips were assembled on the guided-wave circuit using a hybrid integration technique. The insertion loss of the fabricated 4*4 matrix switch was scattered among switching paths and ranged from 26 to 33 dB. The switch was applicable to a 400 Mb/s signal system with a bit error rate of 10/sup -9/. The numerical analysis shows that the residual reflectivity at the LD gate and waveguide facets caused the loss scattering among the paths and that reduction of the residual reflectivity is essential for improving the switch characteristics. >

Refractive index and attenuation characteristics of SiO 2 –Ta 2 O 5 optical waveguide film

The refractive index and optical attenuation of sputtered SiO2–Ta2O5 waveguide film were measured in the 0.633–1.32-μm wavelength region. The waveguide film had a large refractive-index range of 1.46–2.08, which can be adjusted by suitable selection of the composition ratio of the SiO2–Ta2O5 target. Substrate heating, up to 270°C, during the sputtering process was effective for obtaining low attenuation. The waveguide films showed low attenuations, <0.41 dB/cm for the TE0 mode. The best fits of the form λγ to the measured attenuation have γ between 0 and −1, where λ is the wavelength. This wavelength dependence of the attenuation can be interpreted based on mode conversions due to the film surface roughness.

Optical interconnections using a silica-based waveguide on a silicon substrate

Guided-wave optical interconnections for interchip data transmis-sions and clock distributions are demonstrated. The optical interconnection circuit consists of a silica-based guided-wave circuit, laser diodes, and photodiodes. The interconnection topology adopts the star coupler network used in local area networks as a model. The laser diodes and photodiodes are assembled with the guided-wave circuit by the hybrid integration technique. Preliminary experiments on a four-chip interconnection circuit yield a 340 Mbps data rate and a 250 MHz clock frequency.

Guided-wave optical gate matrix switch

An optical gate matrix switch that is made by integrating InGaAsP laser diode gates with high-silica guided-wave splitter and combiner circuits in a hybrid fashion is proposed and demonstrated. It provides point-to-multipoint switching. A preliminary experiment for a 4*4 matrix switch shows that the switch is capable of more than 400-Mb/s bandwidth signal switching. >

Film-level hybrid integration of AlGaAs laser diode with glass waveguide on Si substrate

A ridge-waveguide AlGaAs laser diode (LD) was integrated with a SiO/sub 2/-Ta/sub 2/O/sub 5/ embedded waveguide on a Si substrate by using a film-level hybrid integration technique of semiconductor epitaxial film. CW operation of the LD was achieved at room temperature. The LD-waveguide butt-coupling loss was 9 dB, and the loss due to misalignment was estimated at 3 dB, which corresponds to a displacement of about 1 mu m in both the vertical and lateral directions.<<ETX>>