Design of highly efficient electromagnetic metasurface for terahertz applications

Metasurfaces and terahertz spectrum are promising parts of future communication ecosystems. Nevertheless, studies have shown that reported metasurfaces in this part of the spectrum are not sufficiently efficient. In this research, three different applications at the THz spectrum which are based on metasurface structures are studied as the main topics of research. First, a novel terahertz (THz) spectroscopy system is proposed which is based on a graphene-based metasurface. The proposed sensor operates in reflection mode over a broad range of frequency bands (0.2 − 6 THz) and can detect relative permittivity of up to 4 with a resolution of 0.1 and a thickness ranging from 5 μm to 600 μm with a resolution of 0.5μm. The proposed spectroscopy technique utilizes some unique spectral features of a broadband reflection wave including Accumulated Spectral power (ASP) and Averaged Group Delay (AGD), which are independent of resonance frequencies and can operate over a broad range of the spectrum. Following this, an efficient terahertz (THz) photoconductive antenna (PCA) are proposed. The antenna is designed for THz continuous wave (CW) applications in the frequency range of 0.5-3 THz. Owing to plasmonic excitation, the optical-to-electrical efficiency of photomixer is increased by a factor of 100 while there is a 4-fold reduction in size compared to those with similar radiation features. Finally, a novel metasurface design is proposed for the first time ever which has addressed some fundamental challenges in metasurface design and has introduced dense metasurface for the first time. In this chapter, an algorithm is proposed for the design of metasurface which exploited Delta-Sigma concept from temporal domain to spatial domain to increase the spatial sampling of the incident wave in reflecting/transmission metasurfaces. In this algorithm, the design procedure considers real-world response of the structure instead of conventional analysis of meta- surfaces. The proposed algorithm brings about to achieve very efficient beam-forming of reflecting/transmission metasurface. It is shown that the proposed technique improved the efficiency of metasurface design significantly and can enhance the control over the metasurface design unprecedentedly.