Persistent Link:
http://hdl.handle.net/10150/194018
Title:
Vortex Retarders
Author:
McEldowney, Scott
Issue Date:
2008
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This dissertation addresses the creation of polarization vortex beams. Vortex retarders are components with uniform retardance but a fast axis which rotates around its center with can create polarization vortices. The goal was to develop a simple method for producing vortex retarders for visible wavelengths, with a continuous fast axis, and for multiple vortex modes.The approach was to use photo-aligned liquid crystal polymers (LCP). The target was a halfwave retardance for wavelengths in the range of 540~550nm. A photo-alignment layer was spin-coated onto a substrate, baked, and alignment was set through exposure to linear polarized UV (LPUV) light. The alignment layer was exposed through a narrow wedge shaped aperture located between the substrate and polarizer. Both the polarizer and substrate were continuously rotated during exposure process in order to create a continuous variation in photo-alignment orientation with respect to azimuthal locations on the substrate. The mode of the vortex retarder was determined by the relative rotation speeds. The LCP precursor was spin-coated and subsequently polymerized using a UV curing processes. Elements produced were analyzed by measuring the space variant Mueller Matrix of each component. Our measurements demonstrated that the vortex retarders were half wave plates with a continuous fast axis orientation. Measurement of the center region of the vortex retarders identifies a 100-200um region of disorientation. At 0.5mm resolution, a high depolarization index in the center of the vortex retarders was observed. The DOP was low in the center for a horizontal linear polarized input field but remained high for circular polarized input.The viability of these components was assessed by determining the point spread matrix (PSM) and the optical transfer matrix (OTM) and comparing these to theoretical calculations. The agreement between the measured and predicted PSM was excellent. The major difference was the non-zero response in the m03 and m30 elements indicating circular diattenuation. The OTM comparison between measured and predicted demonstrated an excellent quantitative match at lower spatial frequencies and a good qualitative match at higher spatial frequencies. Measured results confirm that vortex retarders produced using photo-aligned LCP produce near theoretical performance in an optical system.
Type:
text; Electronic Dissertation
Keywords:
Polarization; Liquid Crystals; Polarization Vortex; Polarization Components; Vortex Retarder
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Optical Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Chipman, Russell A.
Committee Chair:
Chipman, Russell A.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleVortex Retardersen_US
dc.creatorMcEldowney, Scotten_US
dc.contributor.authorMcEldowney, Scotten_US
dc.date.issued2008en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis dissertation addresses the creation of polarization vortex beams. Vortex retarders are components with uniform retardance but a fast axis which rotates around its center with can create polarization vortices. The goal was to develop a simple method for producing vortex retarders for visible wavelengths, with a continuous fast axis, and for multiple vortex modes.The approach was to use photo-aligned liquid crystal polymers (LCP). The target was a halfwave retardance for wavelengths in the range of 540~550nm. A photo-alignment layer was spin-coated onto a substrate, baked, and alignment was set through exposure to linear polarized UV (LPUV) light. The alignment layer was exposed through a narrow wedge shaped aperture located between the substrate and polarizer. Both the polarizer and substrate were continuously rotated during exposure process in order to create a continuous variation in photo-alignment orientation with respect to azimuthal locations on the substrate. The mode of the vortex retarder was determined by the relative rotation speeds. The LCP precursor was spin-coated and subsequently polymerized using a UV curing processes. Elements produced were analyzed by measuring the space variant Mueller Matrix of each component. Our measurements demonstrated that the vortex retarders were half wave plates with a continuous fast axis orientation. Measurement of the center region of the vortex retarders identifies a 100-200um region of disorientation. At 0.5mm resolution, a high depolarization index in the center of the vortex retarders was observed. The DOP was low in the center for a horizontal linear polarized input field but remained high for circular polarized input.The viability of these components was assessed by determining the point spread matrix (PSM) and the optical transfer matrix (OTM) and comparing these to theoretical calculations. The agreement between the measured and predicted PSM was excellent. The major difference was the non-zero response in the m03 and m30 elements indicating circular diattenuation. The OTM comparison between measured and predicted demonstrated an excellent quantitative match at lower spatial frequencies and a good qualitative match at higher spatial frequencies. Measured results confirm that vortex retarders produced using photo-aligned LCP produce near theoretical performance in an optical system.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectPolarizationen_US
dc.subjectLiquid Crystalsen_US
dc.subjectPolarization Vortexen_US
dc.subjectPolarization Componentsen_US
dc.subjectVortex Retarderen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorChipman, Russell A.en_US
dc.contributor.chairChipman, Russell A.en_US
dc.contributor.committeememberMansuripur, Masuden_US
dc.contributor.committeememberDereniak, Eustaceen_US
dc.identifier.proquest2559en_US
dc.identifier.oclc659748489en_US
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