Fabrication of non-planar silver nano-arc-gap arrays

We developed a method to fabricate an array of silver non-planar nano-arc-gaps via inverted hemispherical colloidal lithography and shadow metal evaporation methods. It is found that there is a localized surface plasmon mode which results in extraordinary optical transmission. The electric field is strongly localized at the nano-arc-gap region and therefore induces a resonance that has an ultra-small mode volume of less than 2.44 x 10(-6) mu m(3). The ratio of the quality factor to the mode volume is as high as 1.44 x 10(6) mu m(-3). This would be valuable for the design of optoelectric circuits.