This thesis contains contributions to the fields of on-chip THz system simulation and experiment. In experiments, a range of pump-probe transmission on-chip spectroscopy studies were performed in order to investigate the in-plane interaction of terahertz radiation with gated two-dimensional electron systems. Varying the geometry of the gated systems demonstrated novel spectral features related to confined plasmonic modes that were then confirmed by simulations of the same systems using COMSOL multiphysics software.
The devices were explored in a number of ways, including their ability to tune and filter terahertz injected into a mesa using coplanar waveguide, either by magnetic field or applied gate bias. The evolution of magnetoplasmon resonances was observed as a function of magnetic field. Full-wave three-dimensional simulations were compared with the experiments to distinguish bulk and edge magnetoplasmon resonances from one another. Furthermore, it was found that a trapezoidal mesa showed a more complex field pattern, requiring a two-dimensional model, resulting in a richer plasmonic spectrum. Lastly, a more complex device with three additional cavities was created by overlaying a second gate on the mesa. It was demonstrated that the two gates acted independently of one another, and furthermore, that the modes produced by the two gates could potentially couple to one another, although the final evidence for this was quite weak.
As a result of the impact of COVID-19 the laboratory was closed for a period of six months. During this time, THz simulations of planar goubau lines and coplanar
waveguide were conducted using finite element simulation software. It was shown that the fingerprint detection of overlaid lactose (as an exemplar material) could potentially be significantly enhanced by reduction in the dimensions of the coplanar waveguides. Additionally, a tunable terahertz band-stop filter was designed and simulated which comprised of coupled split-ring resonators integrated into planar Goubau-line waveguide. This system allows for the potential observation of resonance splitting dependent on the distance between the resonators that could be dynamically tuned by employing a cantilevered microelectromechanical scheme.
