Enhanced optical transmission through tapered metallic gratings

To achieve non-resonant behavior, we propose a metallic grating device with linearly tapered slits. The tapering provides a gradual impedance variation from the entrance to the exit of the slits, leading to broadband and wide-angle enhanced transmission in the infrared. In addition, the light is strongly localized and enhanced at the slit exits, in contrast with straight slits. We describe the phenomenon with a transmission line model, which is in accordance with rigorous simulations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729005]