Orbital angular momentum and fully structured light in nonlinear media and cavities

Student thesis: Doctoral Thesis

Abstract

The work in this thesis describes interesting phenomena that results from the interaction between high intensity laser light and nonlinear matter. By changing the structure of light's properties such as intensity and polarisation as well as the type of nonlinear action that occurs during propagation through the medium, we aim to describe how the properties of light are affected by the various interactions.Considering down-conversion in a second order x(2) medium we first present a spatiotemporal mechanism for producing two dimensional optical rogue waves in a turbulent state driven by vortices with helical wavefronts. Self-organising hexagonal structures bound in phase lose stability and synchronised oscillations are unstable leading to phaseunbound vortex-mediated turbulence with high excursions in amplitude. Nonlinear amplification leads to rogue waves close to optical vortices, and probability density functions typical of rogue waves.We then consider fully structured light (FSL) within a Kerr x(3) medium. In particular, we describe how the polarisation distribution of FSL beams is affected by propagation. In the linear case we derive an expression for the rotation of the polarisation and show the rotation is due to the difference in Gouy phase between the two eigenmodes in the beam. For nonlinear propagation we show the effect of the cross-phase modulation from self focusing results in additional rotation that can be controlled by changing various physical parameters of the FSL beam like the beam waist and magnitude of OAM.Finally we consider the interaction with the Kerr medium in an optical cavity. Above Turing threshold we observe the formation of peaks upon the FSL structure. Where the beam carries a net orbital angular momentum we observe a rotation in the structure. We detail how the angular velocity of the Turing structure can be controlled by careful selection of the parameters of the FSL beams.
Date of Award23 Aug 2019
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council) & University of Strathclyde
SupervisorAlison Yao (Supervisor) & Gian-Luca Oppo (Supervisor)

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