Yu Tanaka

Low-loss, flat-topped and spectrally uniform silicon-nanowire-based 5th-order CROW fabricated by ArF-immersion lithography process on a 300-mm SOI wafer

We report superior spectral characteristics of silicon-nanowire-based 5th-order coupled resonator optical waveguides (CROW) fabricated by 193-nm ArF-immersion lithography process on a 300-mm silicon-on-insulator wafer. We theoretically analyze spectral characteristics, considering random phase errors caused by micro fabrication process. It will be experimentally demonstrated that the fabricated devices exhibit a low excess loss of 0.4 ± 0.2 dB, a high out-of-band rejection ratio of >40dB, and a wide flatband width of ~2 nm. Furthermore, we evaluate manufacturing tolerances for intra-dies and inter-dies, comparing with the cases for 248-nm KrF-dry lithography process. It will be shown that the 193-nm ArF-immersion lithography process can provide much less excess phase errors of Si-nanowire waveguides, thus enabling to give better filter spectral characteristics. Finally, spectral superiorities will be reconfirmed by measuring 25 Gbps modulated signals launched into the fabricated device. Clear eye diagrams are observed when the wavelengths of modulated signals are stayed within almost passband of the 5th-order CROW.

Si-nanowire-based multistage delayed Mach-Zehnder interferometer optical MUX/DeMUX fabricated by an ArF-immersion lithography process on a 300 mm SOI wafer.

We report good phase controllability and high production yield in Si-nanowire-based multistage delayed Mach-Zehnder interferometer-type optical multiplexers/demultiplexers (MUX/DeMUX) fabricated by an ArF-immersion lithography process on a 300 mm silicon-on-insulator (SOI) wafer. Three kinds of devices fabricated in this work exhibit clear 1×4 Ch wavelength filtering operations for various optical frequency spacing. These results are promising for their applications in high-density wavelength division multiplexing-based optical interconnects.

Silicon photonics optical demultiplexer technology for WDM optical interconnects

We report high-performance silicon-wire-based demultiplexer devices targeted for high-capacity WDM optical interconnects. Two kinds of WDM demultiplexers based on delayed interferometers will be discussed in terms of chip-size and spectral flatness, compared with conventional devices.

Silicon photonics optical DeMUX technology for WDM applications

We report recent progress of high-performance Siwire-based WDM devices based on higher-order microring resonators and multi-stage delayed interferometers fabricated by 300-mm wafer-scale 193-nm ArF-immersion CMOS process.

Three-dimensional Strain Relaxation in the As/Si (001)-(2×1) Surface

Surface X-ray diffraction experiments and elastic-energy calculations have been performed to determine strain relaxation in the As/Si (001)-(2×1) surface. The result of the in-plane analysis shows that symmetric As dimers formed on the Si(001) substrate have a bond length of 2.54 A, while the inward displacement of second-layer Si atoms is 0.19 A in an irreducible (2×1) unit cell. From the subsequent out-of-plane analysis, we confirmed that the Si atoms in the third and fourth substrate layers are displaced upward (x=0.75) and downward (x=0.25) alternately. The observation is supported by an elastic-energy calculation using the Keating model. The determined structure includes in-plane and out-of-plane substrate Si atoms up to the sixth layer. A preliminary measurement of a fractional-order reflection intensity as a function of temperature has shown that the As/Si(001)-(2×1) surface becomes more ordered in the temperature range of 710 to 817 K. The intensity rapidly decreases above 817 K, which is interpreted to be due to the desorption of As2 molecules from the surface with an activation energy of 5.9±1.1 eV.