Terahertz metamaterials : from fundamental coupling mechanisms to new terahertz metasurfaces and functional emitters Zusammenfassung: The central topic of this thesis is the investigation of a new kind of optical materials so called metamaterials. These artificially created materials consist of periodically arranged sub wavelength sized resonant structures. Their optical properties can be designed by changing the form size or arrangement of the sub structures. The resonators interaction among each other and with an incident light field is investigated experimentally in the terahertz regime of the electromagnetic spectrum. In the first part of this thesis the fundamental electromagnetic interaction between one type of sub structure a single Split Ring resonator is investigated in two dimensional arrays.Then the complexity of interaction was increased by adding a second Split Ring inside each unit cell which results in the formation of a particular kind of resonance a so called Fano resonance. The line shape of this sharp asymmetrically shaped resonance was then controlled by the separation between the two resonators.In the third part a new type of optical materials is presented a wave vector selective surface. This ultra thin structured surface can filter out waves which arrive under oblique incident on the surface operating effectively as a tunnel vision filter. In the last part a novel method is presented to excite resonant structures on semiconductor substrates using visible light. As one example this technique is than used as an inverse near field microscope to map the electromagnetic near fields of those resonators with sub wavelength resolution