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Title: Liquid crystals and novel gain materials for thin-film photonic devices
Author: Wood, Simon
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2017
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This thesis describes work to create a variety of thin-film photonic devices based upon liquid crystalline materials. Firstly, a variety of liquid crystal phases are polymer- templated by combining a liquid crystalline material with photo-polymerisable reactive mesogens. Upon photo-curing, a polymer scaffold, which is a template of the original phase, is formed with liquid crystal molecules in interstitial sites. This liquid crystal is removed to yield a polymer scaffold which can be used to template the original phase. Here, polymer-templating is used to template the smectic A liquid crystal alignment onto nematic liquid crystals for the first time; this results in materials with improved contrast ratios and faster response times than conventional nematic devices. Next, a study is performed to compare the electro-optic properties of polymer-templated and polymer-stabilised chiral nematic liquid crystals. The enhanced tuning range of polymer-templated liquid crystals is applied to create a polymer-templated liquid crystal laser and to electrically tune its emission wavelength. Subsequently, thin-film elastomeric liquid crystal lasers are created. The lasing wavelength of these films can be reversibly and selectively tuned without hysteresis by subjecting them to a mechanical stress. Finally, work is performed to study the potential of inorganic materials for use in liquid crystal lasers. Transition metal clustomesogens (liquid crystalline materials that contain highly emissive molybdenum clusters) and inorganic-organic perovskites are considered here. The dispersal and emissive properties of clustomesogens in liquid crystals are studied, and they are used to create circularly polarised light sources with a polarisation that can be controlled using electric fields. Layered structures of inorganic- organic perovskite and liquid crystal are created; these exhibit enhanced amplified spontaneous emission. Then, perovskites are used as the gain materials in distributed feedback lasers for the first time. These lasers may be wavelength-tuned by varying the grating spacing of the structure.
Supervisor: Morris, Stephen Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Photonic devices ; Liquid crystals ; Perovskites ; Lasers ; Elastomers