Optical vortices and their related research in engineering

Abstract

Light beams characterised by a spiral front, or more generally, an optical field exhibiting a circulating current density, are termed optical vortices. This thesis investigates two types of optical vortices: monochromatic vortex beams under paraxial approximation and spatiotemporal vortices, and their related research in engineering. Firstly, for vortex beams, we present a new geometric representation framework called the Total angular momentum-conserving Poincaré sphere (TAM-PS). A wide range of vortex beams can be efficiently characterised by this framework. Additionally, two kinds of braid clusters based on the TAM-PS are introduced, serving as a theoretical cornerstone for vortex beam applications. Furthermore, a method for analysing the orbital angular momentum (OAM) and total angular momentum (TAM) of an unknown vortex beam is introduced. This method aids in analysing the OAM or TAM of vortex beams generated by a meta-surface integrated micro-ring during its design phase based on simulation results. Additionally, a vortex beam reflection computation model is studied, examining the feasibility of using vortex beams as detection signals for light detection and ranging sensors to measure the orientation of reflecting surfaces. Secondly, two controversies regarding spatiotemporal optical vortices (STOVs) are studied: 1. The calculation of transverse OAM; 2. The phase distribution of STOVs in the t-x plane. Additionally, a special kind of STOV, termed the toroidal light pulse, is introduced, and exploratory work on the toroidal momentum for this pulse is presented.

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ORCID for Jize Yan: orcid.org/0000-0002-2886-2847

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