Accessing the Optical Magnetic Near-Field through Babinet's Principle

By: Honghua U. Yang, Robert L. Olmon, Kseniya S. Deryckx, Xiaoji G. Xu, Hans A. Bechtel, Yuancheng Xu, Brian A. Lail, and Markus B. Raschke

ACS Photonics 1, 894 (2014)

Engineering the optical magnetic field with optical antennas or metamaterials extends the ways to control light-matter interaction. The slot antenna, as the electro- magnetic dual of the linear rod antenna, provides the simplest form of a magnetic resonator tunable through its length. Using combined far- and near-field spectroscopy and imaging, and theory, we identify magnetic dipole and higher order bright and dark magnetic resonances at mid-infrared frequencies. From resonant length scaling and spatial near-field distribution, we confirm the applicability of Babinetʼs principle over the mid-infrared spectral region. Babinet's principle thus provides access to spatial and spectral magnetic field properties, leading to the targeted design of magnetic optical antennas.