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Please use this identifier to cite or link to this item: http://hdl.handle.net/1974/7315

Title: Optically Active Chiral Mediums Fabricated with Glancing Angle Deposition
Authors: Yang, Jian

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Keywords: glancing angle deposition
bi-isotropic mediums
discrete dipole approximation
isotropic chiral mediums
Mueller matrix
optical activity
circular dichroism
chiral microparticles
optical rotation dispersion
thin films
Issue Date: 6-Jul-2012
Series/Report no.: Canadian theses
Abstract: Optically active helical microparticles are studied in the forms of thin films, suspensions and powders. From fabricated helical porous thin films, microparticle suspensions are obtained by removing the microparticles (film columns) from their substrates and dispersing them into water. For removing microparticles, four methods are explored and compared: sacrificial NaCl layer, gold (Au) layer, buffered oxide etching, and direct ultrasonic agitation. The primary film material studied in this work is amorphous silicon (Si). Physical morphology of the microparticles is examined with scanning electron microscopy (SEM). Methods employed to characterize optical activity of the microparticles include: polarimetry, spectrophotometry, and spectroscopic ellipsometry (SE). The produced chiral microparticles exhibit optical activity: optical rotation (OR) and circular dichroism (CD - in the form of differential circular transmission (DCT)). Significant findings include: (a) we observe the largest optical rotatory power ever reported in scientific literature, 11◦/μm at 610 nm wavelength for a Si film; (b) for the helical thin films, there is one dominant DCT band in the measured wavelength range; however for microparticle suspensions and powders, there exist two DCT bands: one broad band at long wavelengths, and one narrow band in the short wavelength range; compared to their thin film forms, microparticle suspensions and powders have inverted sign for the broad DCT band. A discrete dipole approximation (DDA) model is employed to calculate optical response (e.g. extinction, scattering, and absorption cross-sections) of the microparticles, so as to enable us to understand the effects of different structural parameters of the microparticles on their optical response. Calculation confirms that optical activity of chiral microparticles is due to coherent light scatterings with the chiral structures of the particles. The inversion in sign of the broad DCT bands of microparticle suspensions and powders is likely due to the averaging effect from random orientation of the helical microparticles, as is indicated both from experimental results and from calculation.
Description: Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-07-06 09:59:20.751
URI: http://hdl.handle.net/1974/7315
Appears in Collections:Queen's Graduate Theses and Dissertations
Department of Physics, Engineering Physics and Astronomy Graduate Theses

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