Surface plasmon propagation on overcrossing metallic waveguides fabricated by a pick-and-place method
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lasmonics, Photonics, and Metamaterials Research Letter
Surface plasmon propagation on overcrossing metallic waveguides fabricated by a pick-and-place method Yusuke Nagasaki, Masashi Miyata, and Mai Higuchi, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan Junichi Takahara, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan; Photonic Advanced Research Center, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan Address all correspondence to Junichi Takahara at [email protected] (Received 29 September 2015; accepted 9 December 2015)
Abstract Plasmonic waveguides can transport light while still confining it beyond the diffraction limit. Recently, crossing plasmonic waveguides have been suggested for the implementation of higher-density optical networks. However, suppressing undesirable scattering at their crossing point is still a challenging task because waveguides in these structures are physically connected. Here, we present an experimental demonstration of surface plasmon propagation on an overcrossing metallic waveguide fabricated by a pick-and-place method. By spatially separating the waveguides, the undesirable interaction at the interconnection can be suppressed. Our approach could be a powerful platform to achieve high-density integration of optical waveguides.
Introduction Plasmonic waveguides[1,2] are metallic optical waveguides that can transport optical information as surface plasmon polaritons (SPPs),[3–5] which are electromagnetic waves coupled to free electron oscillations on a metal surface. As they are capable of confining guided plasmon modes into smaller volumes beyond the diffraction limit at optical frequencies, plasmonic waveguides have recently attracted interest for use as subwavelength optical waveguides in nanoscale optical circuits. To transmit SPPs, various types of plasmonic waveguides, such as cylindrical metal nanorods,[6] slab waveguides,[7] slot waveguides,[8] and metal grooves,[9] have been proposed. In recent years, crossing plasmonic waveguides[10–12] have been suggested for integrated optical components. These structures are composed of several physically connected waveguides placed on a substrate. Compared with bypass wiring without crossing, crossing waveguides make it possible to connect optical devices at shorter distances. This capability leads to decreases in total propagation losses during information transmission. In addition, owing to increases in wiring densities per unit area, these structures are key elements in realizing high-density optical networks and intricately patterned photonic devices. Ideally, an optical signal on a crossing waveguide should be fully transmitted forward through their intersections. Unfortunately, due to scattering at the crossing points, propagating light experiences undesirable energy dissipation such as by radiation to the surroundings, reflection, and energy escaping to sideways (crosstalk), leading to degradation of the signal trans
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