Advanced FBG fabrication for challenging applications

Abstract

This thesis describes work performed for both advancing the fabrication process of fibre Bragg gratings and for a potential application for gratings inscribed by a system employing the improved methods. The aim of the discussed research is to increase the potential for fabricated grating variations whilst maintaining a grating accurate to the initial design and compensating for errors in fabrication. In addition, simulations for a system for detecting nanoparticles is sought, making use of the improvements to the fabrication setup and highlighting an example of the improved fabrication system’s flexibility. As a part of the development of the fabrication system, an increase in the efficiency of grating fabrication is a desired result, primarily via the reduction of grating iterations required to produce a high quality grating. To perform this, automated control of an optical vector analyser was created, for use in a feedback process in which the grating is observed during inscription and compared to simulations for the detection of fabrication errors. This will not only increase the likeness of gratings to their design but will also assist in repeatability of inscription by the system. Other improvements to the fabrication system have also been progressed, such as the inclusion of an optional interferometer inscription head and the ability to fabricate gratings of up to one metre in length. These two discussed factors will increase the flexibility of grating designs that can be written, enabling a greater variety of grating-based research to be available from a single fabrication setup. Potential fabrication designs to demonstrate the capabilities of the system were investigated, leading to the development of a simulation for a nanoparticle detector. Observations of the transmission spectrum as nanoparticles pass through the beam path in an orthogonally aligned microchannel demonstrate alterations to the spectrum which may be used to identify the presence of nanoparticles and some select attributes. How the changes in the wavelength of a valley within the spectrum are affected by variations in parameters is overviewed as well as improvements to the simulations to further develop the accuracy to a physical detection system.