Y. Chen, Y. Chen, J. Chu and Xianfan Xu
ACS Photonics 4, 567-575 (2017)
In this work we report a new type of nanostructure, the bridged bowtie aperture (BBA) antenna, for producing a simultaneously enhanced and confined electric and magnetic near field. The optical nanocircuit theory is employed to reveal its underlying mechanism. The electric near-field distribution of the nanostructure is observed using transmission-type s-SNOM at the nanoscale, and the magnetic near-field distribution is then derived from the electric near field of a complementary BBA structure using Babinet’s principle. To our knowledge, the generation of such an electromagnetic hot spot has never been experimentally demonstrated. Relative to the existing nanostructures that can produce an electromagnetic hot spot, the BBA antenna has apparent advantages, which offers a new approach for nonlinear optics, surface-enhanced spectroscopy, biosensing, and metamaterials.