| 摘要 |
An apparatus includes a first waveguide configured to focus an electromagnetic wave to a focal region, and a second waveguide to further condense the light to an optical spot. The second waveguide includes a metallic structure defining an opening having one end positioned adjacent to the focal region and a multilayer structure positioned in the opening, the multilayer structure including a first layer of dielectric material, and second and third layers of dielectric material positioned on opposite sides of the first layer. A layer of lower index of refraction than that of the first dielectric layer may be positioned adjacent to the inner walls of the opening in the second waveguide to efficiently excite surface plasmons, and propagate them with low loss.
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