Enhanced mid-infrared transmission through nanoscale metallic coaxial-aperture arrays

Using a single interferometric lithography patterning step along with self-aligned pattern-definition techniques, uniform, large-area metallic coaxial arrays with similar to 100-nm toroidal gaps are fabricated. Enhanced ( 5 x) mid-infrared ( 4 mu m) transmission through these sub-wavelength coaxial arrays is observed as compared with that through the same fractional opening area hole arrays as a result of the complex coaxial unit cell. Varying the coaxial dimensions shifts the resonance wavelength and impacts the maximum transmission; design rules are derived. The ability to control the transmission wavelength combined with dramatically enhanced transmission represent a promising path toward nanophotonic applications. (C) 2005 Optical Society of America.