Mapping the coupling between a photo-induced local dipole and the eigenmodes of a terahertz metamaterial

We demonstrate that eigenmodes of a metamaterial structure at terahertz (THz) frequencies can be excited by photo-generation of localized transient dipoles in the semiconductor substrate. We apply this technique to map the coupling of these dipoles to the resonator's near-field. The characteristic metamaterial resonances appear as peaks in the spectrum of the THz radiation emitted from the resonant structures into the far-field. Recording two-dimensional THz emission maps allows us to reproduce the frequency-dependent spatial profiles of the metamaterial's eigenmodes.