Wave propagation in graded material composites with extraordinary properties
Time: Fri 2022-12-16 10.00
Location: H1, Teknikringen 33, Stockholm
Subject area: Electrical Engineering
Doctoral student: Brage B. Svendsen , Elektroteknisk teori och konstruktion
Opponent: Professor Astrid Aksnes, NTNU, Trondheim, Norway
Supervisor: Mariana Dalarsson, Elektroteknisk teori och konstruktion; Martin Norgren, Elektroteknisk teori och konstruktion
In this thesis, electromagnetic wave propagation in graded material composites with extraordinary properties are studied. Two such material composite systems are studied in particular, using both analytical and computational electromagnetic methods.
The first system is used for the development of a promising non-invasive method of cancer treatment based on heating the tumors with inserted gold nanoparticles by means of microwave radiation. A waveguide structure is proposed consisting of a thin dielectric layer with a continuous graded material transition to its surrounding materials to either side of the layer. The thin layer consists of cancer tissue with inserted gold nanoparticles that are driven into electrophoretic oscillation by means of electromagnetic radiation. Analytical solutions for the given waveguide problem are obtained, allowing the calculation of the absorption coefficients within the thin layer only, which is important for assessment of the feasibility of the envisioned medical application. The dispersive dielectric models describing the electromagnetic properties of the relevant biological tissues are proposed and discussed. Numerical simulations done in COMSOL Multiphysics are in excellent agreement with and validate the analytical results.
The second system involves wave propagation from a right-handed material to a left-handed metamaterial in an open boundary system. The two materials are impedance-matched, thus ensuring no reflection, and the graded interface between them is described by a continuous function. Metamaterial composites with spatially varying material parameters have been given an increasing theoretical and experimental interest the last two decades. They are useful for a number of applications, such as transformation optics. In this thesis, the properties of left-handed media are discussed. The field solutions to the impedance-matched graded interface are derived, and a numerical model is developed in COMSOL. The results confirm the extraordinary properties of left-handed media.