Probing the modal characteristics of novel beam shapes
MetadataShow full item record
In this thesis, an investigation into the modal characteristics of novel beam shapes is presented. Sculpting the phase profile of a Gaussian beam can result in the generation of a beam with unique properties. Described in this thesis are Laguerre-Gaussian (LG), Hermite-Gaussian (HG) and Bessel beams (BBs). The diffraction of LG beam modes from a triangular aperture is explored and this effect can be used for the efficient measurement of the azimuthal mode index l that indicates the number of multiples of 2π of phase changes that the field displays around one circumference of the optical axis. In this study, only LG beams with zero radial mode index p, with p + 1 denoting the number of bright high intensity concentric rings around the optical axis, were considered. Then, a powerful approach to simultaneously determine both mode indices of a pure LG beam using the principal component analysis (PCA) algorithm on the observed far-field diffraction patterns was demonstrated. Owing to PCA algorithm, the shape of the diffracting element used to measure the mode indices is in fact of little importance and the crucial step is ‘training’ any diffracting optical system and transforming the observed far-field diffraction patterns into the uncorrelated variables (principal components). Our PCA method is generic and it was extended to other families of light fields such as HG, Bessel and superposed beams. This reinforces the widespread applicability of this method for various applications. Finally, both theoretically and experimentally investigations using interferometry show the definitive linkage between both the radial and azimuthal mode indices of a partially coherent LG beam and the dislocation rings in the far-field cross-correlation function (CCF).
Thesis, PhD Doctor of Philosophy
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unportedhttp://creativecommons.org/licenses/by-nc-nd/3.0/
Except where otherwise noted within the work, this item's license for re-use is described as Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.
Showing items related by title, author, creator and subject.
Internal physiology of live krill revealed using new aquaria techniques and mixed optical microscopy and optical coherence tomography (OCT) imaging techniques Cox, Martin; Kawaguchu, So; King, Robert; Dholakia, Kishan; Brown, C Tom A (2015) - Journal articleThe accurate observation of physiological changes on in vivo samples of important animal species such as Euphasia superba (Antarctic krill) is an important goal in helping to understand how environmental changes can affect ...
Lee, Woei Ming (University of St Andrews, 2010-06-25) - ThesisThe two main themes in this thesis are the implementation of interference methods with optically trapped particles for measurements of position and optical phase (optical interferometric metrology) and the optical manipulation ...
Dynamics of optically levitated microparticles in vacuum placed in 2D and 3D optical potentials possessing orbital angular momentum Arita, Yoshihiko; Mazilu, Michael; Chen, Mingzhou; Vettenburg, Tom; Aunõn, Juan M.; Wright, Ewan M.; Dholakia, Kishan (SPIE, 2017-05-19) - Conference itemWe demonstrate the transfer of orbital angular momentum to optically levitated microparticles in vacuum . We prepare two-dimensional and three-dimensional optical potentials. In the former case the microparticle is ...