Feasibility of low-loss and high-speed plasmonic components and circuits

　　Plasmonic components and circuits have been researched and developed for various applications, especially for plasmonic integrated circuits (ICs). This paper clarifies the applicability of plasmonic devices in nano- and... [ view full abstract ]

　　Plasmonic components and circuits have been researched and developed for various applications, especially for plasmonic integrated circuits (ICs). This paper clarifies the applicability of plasmonic devices in nano- and micro-scale circuits from the viewpoint of plasmonic signal transmission loss and speed.

   In silicon ICs, wire delay and power consumption are serious problems. To solve these issues, optical interconnection techniques have been introduced to silicon ICs; however, this has caused other problems, namely a mismatch in size and of the materials between the optical and electronic components. Additionally, the optical components require complicated structures. These issues can be solved using plasmonic components. Therefore, we have developed various plasmonic components for ICs (see Fig. 1) in which surface plasmons are used as signal carriers transmitted at the speed of light. However, signal transmission loss is a growing concern in such plasmonic circuits and will determine the application range of plasmonic components.

    The signal transmission distance in plasmonic circuits is limited by ohmic and radiation loss. We have confirmed that low loss plasmonic component structures integrated on a silicon substrate can be fabricated by patterning a SiO₂ film on a metal film. For some waveguides, the energies required to detect plasmonic and electric signals after propagation were estimated at a bit error rate of 10^-9 according to Conway [Optics Exp., vol. 15, p. 4474, 2007.] and is shown in Fig. 2. The wavelength of the surface plasmons was set to 1550 nm. The energy dissipated per bit was lower in the plasmonic waveguide than in the electric wiring within a few hundred micrometers. The transmission speed of plasmonic signals was much higher than that of the electric signals, where the speed was limited with dispersion in plasmonic waveguides and capacitance in electric wiring. These results demonstrate that we can fabricate plasmonic components and circuits with lower losses and higher operating speeds than by using electric wires.