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

Abstract

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-P Pm 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. . INTRODUCTIONAs the scaling of complementary metal oxide semiconductor (CMOS) technology proceeds, it will become increasingly difficult for conventional copper interconnects to satisfy the design requirements of delay, power, bandwidth, and noise [1]. An on-chip optical interconnect with Si photonics is one of the more promising technologies for overcoming these difficulties in future high-performance computing [2,3]. A waveguide-integrated photodiode (PD) with an ultrawide-band and a small footprint is one of its key components. A Si PD has potential compatibility with CMOS technology, but its quantum efficiency is known to be much smaller at wavelengths of 700-900 nm than that of widely used GaAs PDs, which results in a much larger active volume. To overcome the trade-off between speed and responsivity, we have reported on an efficient light coupling and confinement architecture by using a surface plasmon (SP) resonance structure [4]. SP is essentially localized at the interface between a metal and a dielectric material, and the SP antenna is expected to achieve optical energy confinement as well as efficient light coupling between a waveguide and a Si absorption layer. As for waveguides to be coupled with a Si PD, silicon oxynitride (SiON) waveguides are very promising because of their controllability over a large range of refractive indices and their high transparency at wavelengths from 700 to 900 nm [5], where a Si PD has responsivity.In this paper, we report low-loss and high-accuracy 3-dB branching SiON waveguide properties on a Si platform, and an enhanced efficiency of a waveguide-integrated Si nano-PD with an SP antenna. We further report its application to a prototype on-chip optical clock distribution demonstration with a 4-branching H-tree structure.

Proposal for a Plasmonic Mach–Zehnder Modulator Utilizing Quantum Interference Effect

“…Plasmon waveguides and related devices for photonics technologies have attracted continuously increasing interest in recent years, because these devices are expected to allow device sizes much smaller than the diffraction limit and provide the integratability and novel functionalities of the CMOS and photonics circuits [2]- [6]. Manuscript Among these devices, the plasmon modulator is one of the devices most in demand for the integrated CMOS and photonics circuits.…”