Takeo Maruyama

Reduction of Wavelength Dependence of Coupling Characteristics Using Si Optical Waveguide Curved Directional Coupler

Directional couplers are widely used as one of the key components of optical integrated circuits. However, the coupling efficiency of the conventional directional coupler is highly sensitive to wavelength. This sensitivity degrades the characteristics of devices that contain directional couplers for wavelength division multiplexing transmission. A curved directional coupler has been proposed using silica optical waveguide as one of the coupler which realize wavelength insensitive, small footprint and tolerant to fabrication. In this paper, we theoretically investigated this curved coupler using Si wire waveguide and got results that the curved coupler whose bending radius of 21 μm and coupling length of 7.40 μm can reduce the wavelength dependence and achieve about a sevenfold enhancement of operational bandwidth in the transmittance variation range of -3 ± 0.1 dB compared with conventional directional coupler.

GHz response of metamorphic InAlAs metal?semiconductor?metal photodetector on GaAs substrate

We fabricated metal?semiconductor?metal (MSM) photodetectors on the metamorphic InAlAs layer grown on a GaAs substrate. The devices were measured at a wavelength in the 0.8 ?m regime. The receiving area is 30 ? 30 ?m2 and the electrode spacings are 2, 1, and 0.4 ?m. At the electrode spacing of 1 ?m, a dark current of 125 nA was obtained at a bias voltage of ?15 V. At a wavelength of 830 nm, a responsivity of 0.13 A/W was obtained at a bias voltage of ?15 V. At a wavelength of 850 nm, the maximum bandwidth of 9 GHz was obtained at a bias voltage of ?15 V.

Propagation of lossy wave in Si slot waveguide

In order to realize the Si based optical waveguide, which can propagate the absorption wavelength in Si, we theoretically and experimentally investigate the material propagation loss of silicon-on-insulator slot waveguide at 1050 nm.

High-efficiency optical coupling to planar photodiode using metal reflector loaded Waveguide grating coupler

We propose a high-efficient vertical optical coupler using an amorphous Si waveguide grating coupler with top reflector. The coupling efficiency of 80% is calculated at the grating period of 380 nm and the duty ratio of 0.75 with top metal reflector.

GHz response of Si photodiodes fabricated with 0.35-µm Si BiCMOS technology

We fabricated Si photodiode from 0.35 μm BiCMOS process and measured the sensitivity and the frequency response at the wavelength of 650nm. The responsivity was 0.11 A/W and the bandwidth was about 1 GHz.

Ferroelectric properties of PZT and PLZT films on Si substrate with ITO buffer layer

PZT and PLZT films on Si substrates were deposited to realize electro-optic modulators on LSI chip. The coercive field and remnant polarization of PZT and PLZT film were 148kV/cm and 50μC/cm², 170kV/cm and 32μC/cm², respectively.