Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.552022
Title: Optical micromanipulation using ultrashort pulsed laser sources
Author: Little, Helen
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 2007
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Abstract:
In this thesis two previously separate fields of study are brought together: optical micromanipulation and ultrashort laser research. Here, the benefits of combining the high peak powers of ultrashort pulsed lasers and conventional optical micromanipulation techniques are explored. As optical trapping has been studied extensively, the focus of this research is on optical guiding. Moreover, the emphasis is on the use of Bessel beams as these have been shown to offer greater guiding distances than comparable Gaussian beams. The studies within this thesis show that optical guiding in Bessel and Gaussian beams is governed by the average power of the laser. However, the benefits of guiding with ultrashort pulsed lasers to exploit multi-photon processes become evident as the demonstration of simultaneous optical guiding and second harmonic generation in microscopic nonlinear crystal fragments is detailed. This work is developed by using ultrashort pulses to induce two-photon excitation-induced fluorescence in the guiding medium. This allows direct visualisation of the beam-particle interaction and measurement of the reconstruction of the Bessel beam around an object. Some studies using two-photon excitation to investigate Bessel beam penetration through turbid media are discussed. Finally, the work is concluded by exploring the use of pulsed white-light lasers in optical guiding. The wavelength-dependent propagation and reconstruction properties of the white-light Bessel beam are studied before some preliminary optical guiding experiments are discussed. From this, the broad bandwidth of the supercontinuum source is found to offer extended guiding distances in Gaussian beams thereby negating the need for Bessel beams.
Supervisor: Dholakia, Kishan; Sibbett, Wilson Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.552022  DOI: Not available
Keywords: Bessel ; Supercontinuum ; Multiphoton excitation ; Optical micromanipulation ; Femtosecond lasers ; QC689.5L35L5 ; Laser manipulation (Nuclear physics) ; Micrurgy ; Laser pulses ; Ultrashort
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