The coupling of volume and surface fields facilitated by two-dimensional (2D) periodic surface lattices (PSLs) of both cylindrical and planar topology is considered. All the PSLs presented in this work have shallow corrugation allowing the lattice to be described as an effective metadielectric. An analytical dispersion equation describing the hybrid eigenfield of a PSL based on a cylindrical waveguide is derived. The cylindrical structures are designed to have a large diameter, enhancing their potential for use as the interaction region of an active device when combined with an appropriate electron beam. Due to the structureâs large diameter, a theoretical model describing some of the possible scattering processes, is developed for planar geometry. Coupled wave equations and an analytical expression for the coupling coefficient are presented. A dispersion study, based on this theory, shows that the properties of the structure are tailored by varying the lattice parameters, and the PSLâs capability of supporting a Cherenkov interaction is demonstrated.Experimental measurements of planar PSLs resembling mesh structures, carried out at 140-220 GHz, show sharp resonances corresponding to the PSLâs surface field. When mounted on a suitable metal-backed dielectric substrate, the PSLs exhibit coherent cavity eigenmode formation. The individual lattice elements are coherently synchronised by the surface field and volume field confined within the dielectric, demonstrating the principle of mode selection. Measurements of a planar PSL designed to operate at the 325-500 GHz frequency band are presented, demonstrating the scalability of the PSLs. Dispersion plots, obtained by modelling the planar PSLs using CST Microwave Studio, indicate the frequency positions of the expected cavity eigenmodes. When compared to the experimental results and theoretical dispersions, some correlation is observed.
|Date of Award||17 Mar 2016|
- University Of Strathclyde
|Sponsors||EPSRC (Engineering and Physical Sciences Research Council)|
|Supervisor||Adrian Cross (Supervisor) & Craig Robertson (Supervisor)|