Terahertz sensing with meta-surfaces and integrated circuits

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, meta-surfaces 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.