The repetition frequency of modelocked laser diodes was increased to 860 GHz. This modelocking frequency was controlled simply by adjusting the position of a single saturable absorber in the asymmetric colliding pulse device geometry.

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A strong enhancement of the ${\mathrm{Er}}^{\text{3+}}$ -related 1.54 μm emission was obtained from Er-doped porous silicon (PSi), when host PSi was slightly oxidized before Er incorporation. Separate measurements of the energy transfer and the Auger deexcitation between carriers in Si crystallites of preoxidized PSi and ${\mathrm{Er}}^{\text{3+}}$ ions were measured as functions of the preoxidized time or the thickness of the ${\mathrm{SiO}}_2$ interlayer, and revealed that a 1 nm order thick ${\mathrm{SiO}}_2$ interlayer between Si crystallites and ${\mathrm{Er}}^{\text{3+}}$ ions suppressed the Auger energy backflow strongly with only a moderate decrease of the carrier mediated ${\mathrm{Er}}^{\text{3+}}$ excitation. A thin ${\mathrm{SiO}}_2$ interlayer was also effective at suppressing the phonon-assisted energy backtransfer at high temperatures, leading to a strong room temperature ${\mathrm{Er}}^{\text{3+}}$ -related 1.54 μm emission.

Optical transmitter and receiver ICs, each with a footprint of 25 mm ² , were fabricated using a silicon photonics platform based on 40-nm-node CMOS technology. High-speed transmissions of data at 300 Gbps were demonstrated. The wire-type waveguide (WG) in the transmitter IC had a width of 350 nm and a height of 200 nm, and in the completed optical IC, it showed low propagation loss (1.62 dB/cm) for the O-band transverse electric mode and low propagation loss variation (0.15 dB/cm) at 3σ. The coupling loss of the grating couplers was reduced to 2.7 dB by using an apodization structure with a narrow trench width of 70 nm. The wafer-scale reproducibility of the WG width was excellent, as confirmed by a spectral variation analysis using a large number of the microring resonators. The surface-illumination photodetectors (PDs) of the optical receiver were made using a germanium epitaxial film and had a leakage current of less than 10 nA at 3 V and a responsivity of 0.75 A/W. The modulation efficiency of the PN-junction-type Mach-Zehnder modulators of the optical transmitter was 1.3 V ^. cm at 0 V. The uniformity of the PDs and modulators on a 300-mm wafer was very high. By using the fabricated optical transmitter and receiver ICs, data transmissions at up to 12 × 25 Gbps in the O band (1.3 μm) were demonstrated. Furthermore, low-loss filtering operation in 1:4 channel delayed interferometer-based demultiplexing was shown to enable even faster data transmissions. These results indicate that our silicon photonics platform is very useful for fabricating wideband optical ICs.

This paper reports a hybrid integrated light source fabricated on a silicon platform using a 1.3 μm wavelength quantum dot array laser. Temperature insensitive characteristics up to 120 °C were achieved by the optimum quantum dot structure and laser structure. Light output power was obtained that was high enough to achieve an optical error-free link of a silicon optical interposer. Furthermore, we investigated a novel spot size convertor in a silicon waveguide suitable for a quantum dot laser for lower energy cost operation of the optical interposer.