Radial pattern formation of microparticles under photonic forces: An experimental and theoretical study

Haldar, Arijit (2011) Radial pattern formation of microparticles under photonic forces: An experimental and theoretical study. Masters thesis, Indian Institute of Science Education and Research, Kolkata.

PDF (MS-Thesis of Arijit Haldar, Student of 2006 Batch) arijit_MS_thesis.pdf - Accepted Version Restricted to Repository staff only Download (2MB)

Abstract

Chapter 1 introduces the reader to the field of optical tweezers. The chapter briefly discuses the history and applications of optical traps in the field of physics and biology. The chapter also mentions the work done in microparticle pattern formation using optical tweezers, followed by a general overview of the studies and the task undertaken in this thesis on radial pattern formation. Chapter 2 gives an elaborate and detailed description of the experimental setup used to observe the spontaneous formation of radial patterns in optical tweezers. It also discuses the dependence of these structures on various experimental parameters, that were studied meticulously in the laboratory. Finally it informs the reader about the inadequacies of the already existing phenomenon to explain the observed pattern formation and puts forward justifications for modeling the electric field in the trap region. Chapter 3 is entirely devoted to the theoretical formalism that was used to derive a model for the focusing of a laser beam by high numerical aperture lens into stratified dielectric media. This model is supposed to mimic the conditions of beam focusing inside the trapping chamber of an optical tweezer. Chapter 4 gives the results that were obtained using the theoretical calculations in Chapter 3 , and the parameters from the setup discussed in Chapter 2 . The chapter ends by providing a plausible explanation for the formation of radial patterns that were observed. Chapter 5 mentions the future extensions and improvements regarding the work done in this thesis. It highlights various experimental and theoretical investigations that can be carried out to validate the model further, or to refine it to include the explicit calculation of forces and effects of optical binding .

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