Waveguide-integrated Si nano-photodiode with surface-plasmon antenna and its application to on-chip optical clock signal distribution

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.