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dc.contributor.authorMcLaren-Jones, Jennifer Sian Elizabeth
dc.date.accessioned2019-01-23T16:20:03Z
dc.date.available2019-01-23T16:20:03Z
dc.date.issued2019-04-27
dc.date.submitted2018-05-25
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/288382
dc.description.abstractFor the last 20 years, there has been considerable interest in chiral nematic liquid crystal band edge lasers. The birefringent molecules of chiral nematic liquid crystals form a periodic helical structure, which results in a photonic bandgap for circularly polarised light with the same sense of rotation as the helix. A large increase in effective gain is seen for a fluorescent gain medium within the liquid crystal at the band edges, resulting in lasing. Applications of liquid crystal lasers could include miniature medical diagnostic tools, large-area holographic laser displays, and environmental sensing. The wavelength of emission from dye-doped chiral nematic liquid crystals is highly flexible, with lasers demonstrated across the visible range and near infra-red.This thesis investigates two routes for improving the functionality of chiral nematic liquid crystal lasers, supported by mathematical modelling of expected lasing wavelengths based on reflection and transmission by anisotropic layers. Perovskite is tested as a replacement for fluorescent laser dyes as a gain medium,both in the form of quantum dots dispersed in liquid crystal, and as films placed in liquid crystal structures. It is shown that while the perovskite tested provides some emission, it is not compatible for lasing in these devices, and suggestions for building on these results are made. In-plane switching is tested and developed as a means to achieve tuning of the laser wavelength, demonstrating a continuous wavelength shift of 15 nm, from 600.71 nm to 585.03 nm, over a voltage range of 100 V. This is an improvement on previous tuning in related devices, and may be extended with optimisation of cell thickness,electrode geometry, and initial lasing wavelength. Accurate descriptions of the refractive index profile of the liquid crystal and perovskite are developed and included in mathematical modelling, in addition to descriptions of the wavelength-dependent gain of a laser dye and perovskite. Suggestions for developing this modelling are made, particularly by the inclusion of accurate modelling of the distortion caused by in-plane switching.
dc.language.isoen
dc.rightsAll rights reserved
dc.rightsAll Rights Reserveden
dc.rights.urihttps://www.rioxx.net/licenses/all-rights-reserved/en
dc.subjectliquid crystal
dc.subjectlaser
dc.subjectphotonic
dc.titleBand edge lasing in chiral nematic liquid crystals
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.publisher.departmentEngineering
dc.date.updated2019-01-23T14:40:45Z
dc.identifier.doi10.17863/CAM.35680
dc.publisher.collegeGonville & Caius
dc.type.qualificationtitlePhD in Engineering
cam.supervisorWilkinson, Timothy
cam.thesis.fundingfalse


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