Fabrication and characterisation of cellulose-based optical fibres

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The numerous beneficial properties of the biopolymer cellulose promote its use in optoelectronic devices. The aim of the present project is the fabrication and characterization of cellulose-based biopolymer optical fibers for optical waveguiding. For this purpose, the influence of different solvents on the optical properties (transmission, absorption, refractive index profile) of the regenerated cellulose is investigated. For this purpose, different cellulose types are dissolved in the respective solvent systems, coagulated via diffusion processes to regenerated cellulose films and then optically characterized. In addition to pure cellulose, various cellulose derivatives are also examined optically. Based on the optical characteristics, core-cladding optical waveguide structures can be generated from the respective materials via a wet-spinning process. For this purpose, a wet-spinning device is being developed that produces fibers for optical waveguides from cellulose and cellulose derivatives that are as defect-free as possible. The optical properties of the cellulose are manipulated by chemical modifications in order to reduce the overtone oscillations caused by the hydroxyl groups and thus to be able to adjust the attenuation curve in a targeted manner. In addition to a single core-cladding structure, multi-core-cladding structures will also be produced from the developed fibers. The optical fibers are then tested for their resistance to radiation, temperature and moisture. In addition, the fibers are tested for their biodegradability using a respirometer. The characterization of the fabricated cellulose-based biopolymer optical fibers includes comprehensive analysis using scanning electron microscopy and light microscopy. Optical properties, such as light waveguidance, are determined via UV/VIS and NIR spectrometers. Crystallinities are determined by X-ray diffraction.