An active terahertz magneto-plasmonic device based on a cobalt aperture array

Summary form only given. We demonstrate the ability to control the transmission of freely propagating terahertz radiation using a magnetic field. This is accomplished using a periodic array of subwavelength apertures fabricated in a free-standing metal foil coated in cobalt. Using a transverse magnetic field that corresponds to the Voigt geometry, we observe a quadratic change in the terahertz amplitude as a function of the applied magnetic field and dramatically larger than the response observed in any equivalent structure at optical frequencies.