R. Kou

Avalanche-mode operation of a simple vertical p-i-n germanium photodiode coupled with a silicon waveguide

Avalanche-mode operation has been observed in a simple p-i-n germanium photodiode coupled with a silicon waveguide. Avalanche gain of ∼ 3 was observed when a 15-V reverse bias was applied to a 1-µm-thick epitaxially-grown germanium layer. This result suggests the possibility of a simple avalanche structure without a silicon multiplication layer.

Ultra-fine metal gate operated graphene optical intensity modulator

A graphene based top-gate optical modulator on a standard silicon photonic platform is proposed for the future optical telecommunication networks. On the basis of the device simulation, we proposed that an electro-absorption light modulation can be realized by an ultra-narrow metal top-gate electrode (width less than 400 nm) directly located on the top of a silicon wire waveguide. The designed structure also provides excellent features such as carrier doping and waveguide-planarization free fabrication processes. In terms of the fabrication, we established transferring of a CVD-grown mono-layer graphene sheet onto a CMOS compatible silicon photonic sample followed by a 25-nm thick ALD-grown Al2O3 deposition and Source-Gate-Drain electrodes formation. In addition, a pair of low-loss spot-size converter for the input and output area is integrated for the efficient light source coupling. The maximum modulation depth of over 30% (1.2 dB) is observed at a device length of 50 μm, and a metal width of 300 nm. Th...

Optical power stabilization using a germanium photodiode and a variable optical attenuator integrated on a silicon wire waveguide platform

We have demonstrated fast optical power stabilization using a germanium photodiode and a silicon variable optical attenuator monolithically integrated on a compact silicon photonic platform. These integrated devices work synchronously with a ∼100-MHz bandwidth. With an external electronic feedback circuit, the output power of the device is stabilized within an error of 3.7 dB for 20-dB input power variation. Feedback response time is about 100 ns.

Graphene optical modulator on silicon waveguide controlled by fine metal-top gate

We proposed a fine-metal gated graphene optical modulator on a CMOS compatible silicon photonic platform. A maximum extinction ratio of 1.2dB is realized by using a 25-nm thick Al2O3 gate capacitor. Optimized device structure and initial Fermi energy dependences are discussed.

Silicon-silica monolithic photonic integration platform for telecommunications applications

For telecommunications applications of highly-integrated silicon-based photonic devices, we have developed a silicon-silica monolithic photonic platform, in which high performance silica-based passive devices and compact, high-speed silicon-based dynamic/active devices can be monolithically integrated.

Silicon photonic platform for telecommunications applications

Various photonic devices covering passive to active functions have been developed and monolithically-integrated on a silicon wire waveguide platform. State-of-art fabrication technologies and unique device designs are overcoming obstacles to practical telecommunications applications.

Optical Interconnection based on Silicon photonics

Electronics CMOS compatible Today’s advanced information society has reached its present state through the combination of high performance electronic circuits for processing information and large-capacity, high-speed communications networks for transmitting information. This mechanism is supported by silicon integrated electronic circuit technology, which provides high-speed, large-scale integrated circuits (LSIs) and by optical communications technology, which provides large-capacity and high-speed communications. If the advanced information society is to continue to expand, the processing performance of electronic circuits must be improved and optical networks must offer even greater capacities and higher data-transfer speeds. However, higher processing speed consumes larger power, which results in rapid temperature increases and limits the performance of LSIs. Furthermore, the dramatic increase in the power consumed by the huge number of electronic appliances and networks that connect them becomes a serious issue of growing concern from the viewpoint of reducing the load on the global environment. At present, optical interconnection technology is considered as one way of controlling power consumption while maintaining the trend toward high-performance electronic circuits and appliances. Optical interconnection will provide high-speed, large-capacity data transmission with high energy efficiency between LSIs and those appliances. On the other hand, currently available optical devices are too large to obtain high-density integration and the cost is high. Fig. 1. Concept of Si photonics technology.