Abstract
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.