Low-Loss Surface-Plasmon Waveguides for Optical Communications

Abstract: Surface-plasmon waves guide light along the interface between two materials with real dielectric constants of opposite sign, i.e. a dielectric and a metal. Thin-film « 50nm) metallic waveguides are predicted to support low-loss surface-plasmon modes at communications wavelengths near 1550 nm.[I] Compared to traditional dielectric waveguides, metallic surfaceplasmon (SP) waveguides support only one polarization state, offer a highly planar, simple to fabricate structure, and can carry electrical, as well as optical, signals. As a result, surfaceplasmon waveguides may provide an alternative to dielectric waveguides for miniaturizing and integrating optical communications components. The absorption loss of both one and two dimensional surface-plasmon waveguides has been analyzed [I, 2]; however, the only experimental measurement of propagation loss suggests that scattering losses dominate over absorption losses.[3] Currently, there is no published analysis of scattering losses for SP waveguides. Moreover, no one has analyzed or experimentally measured SP waveguide bending loss, despite the universal requirement to change the direction of light on an integrated chip. For surface-plasmon waveguides to be considered an alternative to dielectric waveguides, these outstanding questions about waveguide loss mechanisms must be resolved. The proposed research seeks to determine the suitability of surface-plasmon waveguides for integrated-optical communications components. We will numerically model scattering and bending losses for rectangular thin-film SP waveguides and establish designs optimized for minimum loss. We will fabricate these optimal waveguides and compare the measured losses to the predictions of our models. The combined analytical and experimental results will establish which communications components would benefit from implementation with surface-plasmon waveguides.