Investigating a Phase Conjugate Mirror for Magnon-Based Computing

Abstract

This thesis reports on the realisation of a phase conjugate spin wave device employing a four-wave mixing process. Unexpected nonlinear behaviour was revealed in further experiments which are reported on latterly.Chapter 1 introduces the motivation for this thesis: the need to avoid the stagnation of technological progress by investigating alternative computing paradigms, namely magnon-based computing. An introduction to the field of magnonics and magnon behaviour is presented, followed by a brief introduction to nonlinear behaviour.Chapter 2 builds on the general description of spin waves and introduces the concept of phase conjugation. Following an optical treatment of phase conjugation via fourwave mixing, a theoretical description of the phase conjugation in the spin wave regime is presented.Chapter 3 details the experimental materials and methods employed in the succeeding chapters. A description of the antenna design and fabrication processes is presented along with a description of the key experimental equipment.Chapter 4 describes an experimental investigation concerning the realisation of a phase conjugate mirror via four-wave mixing created in a spin wave system. It is demonstrated through experiments and simulations that the mirror is at its most reflective when a standing spin wave is present across the width of the magnon waveguide.Chapter 5 investigates a time-domain fractal arising from the spatio-temporally periodic potential that occurs as a result of the standing wave. The onset of greatgranddaughter fractal modes is observed and the frequency dependence of the amplitude of the fractal modes is discussed.Chapter 6 offers concluding remarks, and considers future experiments that may develop the field.