Many applications of terahertz technology are concerned with sensing of substances such as drugs, chemical compounds, explosives and much more. For this purpose, low-cost terahertz measurement systems are desired. In this respect, metasurfaces can be used as sensitive near-field sensors by exploiting the change of resonant frequency in the vicinity of substances. We demonstrate chip-based terahertz sensors that can be applied to measure the thickness of ultra-thin materials with a resolution of the order of 1/16000 of the wavelength. Furthermore, we show that the same sensor can be used for refractometric measurements. In this context, we evaluated the refractive index of highly absorptive liquids and liquid mixtures. Based on these measurements, we retrieved the mixing ratio of the liquid mixtures. Moreover, we show that meta-surfaces can be employed to implement chip-based terahertz circuits for highly confined surface waves. The electromagnetic properties of the meta-surface can be designed on purpose. For example, such meta-surfaces can serve as integrated interferometric sensors and can be used for highly sensitive measurements when only a small amount of a sample material is available. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

We present experimental und numerical investigations on the excitation, optimization and propagation of terahertz surface waves on silicon substrates. A single metamaterial layer is used to enhance the spatial confinement of the surface wave at the interface between air and silicon. The electric terahertz field of the surface wave is measured by a 2D near field scan.

In search of new technologies for optimizing the performance and space requirements of electronic and optical micro-circuits, the concept of spoof surface plasmon polaritons (SSPPs) has come to the fore of research in recent years. Due to the ability of SSPPs to confine and guide the energy of electromagnetic waves in a subwavelength space below the diffraction limit, SSPPs deliver all the tools to implement integrated circuits with a high integration rate. However, in order to guide SSPPs in the terahertz frequency range, it is necessary to carefully design metasurfaces that allow one to manipulate the spatio-temporal and spectral properties of the SSPPs at will. Here, we propose a specifically designed cut-wire metasurface that sustains strongly confined SSPP modes at terahertz frequencies. As we show by numerical simulations and also prove in experimental measurements, the proposed metasurface can tightly guide SSPPs on straight and curved pathways while maintaining their subwavelength field confinement perpendicular to the surface. Furthermore, we investigate the dependence of the spatio-temporal and spectral properties of the SSPP modes on the width of the metasurface lanes that can be composed of one, two or three cut-wires in the transverse direction. Our investigations deliver new insights into downsizing effects of guiding structures for SSPPs.

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