Nano-photodiodes with a subwavelength active area using the optical near-field enhanced by surface plasmon resonance are proposed. We fabricated a Si Schottky photodiode that consists of an active area of 300 nm in diameter and a surface plasmon antenna to generate the carrier within the active area efficiently. The fabricated photodiode shows an increase of the photocurrent by several tenfold compared to that without a surface plasmon antenna. This result suggests an enhanced photogeneration of carriers in a semiconductor via surface plasmon resonance. Such a Si nano-photodiode is a potential high-speed optical signal detector because the opto-electronic conversion process occurs within a subwavelength scale.

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Engineers are currently facing some technical issues in support of the exponential performance growths in information industries. One of the most serious issues is a bottleneck of inter-chip interconnects. We propose a new "Photonics-Electronics Convergence System" concept. High density optical interconnects integrated with a 13-channel arrayed laser diode, silicon optical modulators, germanium photodetectors, and silicon optical waveguides on single silicon substrate were demonstrated for the first time using this system. A 5-Gbps error free data transmission and a 3.5-Tbps/cm(2) transmission density were achieved. We believe that this technology will solve the bandwidth bottleneck problem among LSI chips in the future.

We developed a waveguide-integrated Si nano-photodiode (PD) with a surface plasmon (SP) antenna for on-chip optical clock distribution. The interfacial periodic nano-scale metal–semiconductor–metal Schottky electrodes were shown to function as an SP optical antenna and also as an optical coupler between a SiON waveguide and a very thin Si-absorption layer. Furthermore, a very high speed response of 17 ps as well as enhanced photoresponsivity was achieved for a 10-µm coupling length. By using this technology, we fabricated a prototype of a large-scale-integration (LSI) on-chip optical clock system and demonstrated 5 GHz of optical clock circuit operation connected with a 4-branching H-tree structure.