New methods for controlling coupling effects in cavity magnon-polariton systems
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Date
2019
Authors
Hyde, Paul
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Abstract
By mediating interactions between light and matter, polaritons offer a window into the fundamental nature of material dynamics and have enabled the development of modern wireless communications technologies. In microwave cavity systems, confined photons interacting with coherent magnon excitations can produce high rates of light-matter coupling and allow the properties of the cavity magnon-polaritons coupling these systems to be studied in new detail. In this dissertation, we employ microwave cavity systems to develop new methods for controlling the coupling properties of cavity magnon-polaritons. We demonstrate that magnon-polariton coupling can be used to indirectly couple two orthogonal cavity resonance modes together, using their mutual coupling to a resonant magnetic system as a bridge across which energy and dynamic information can be transferred. The strength of this indirect coupling can be controlled through tuning the resonant properties of the individual cavity or magnon systems, and in future may be employed to link many photon and magnon systems together. Using a specially designed cavity system, we are also able to compare the coupling effects seen in cavity magnon-polariton systems to those observed in polariton systems involving non-magnetic excitations. These measurements show that the dynamics of polariton coupling are common throughout all systems, but that in cavity magnon-polariton systems the averaged permeability of the entire cavity-material volume plays an important role in determining the strength of coupling effects. We further study the properties of magnon-polariton coupling in systems where the magnon mode has been excited to amplitudes where non-linear effects become significant. We find that bistable resonance properties related to those observed in uncoupled non-linear magnon systems are present in these systems, and that further bistable behaviours unique to coupled systems can be created by controlling the individual properties of the cavity or magnon systems. By uncovering new properties of light-matter coupling in cavity magnon-polariton systems and new methods for controlling this coupling, this dissertation reveals a host of potential applications for these systems in future data storage and processing technologies, and additionally shows that the observed coupling dynamics can be extended into other varieties of polariton systems involving non-magnetic excitations.
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Keywords
Spin-photon coupling, Spintronics, Light-matter coupling, Coupling effects, Polaritons, magnon-polaritons