Planar fluid-tunable waveguide arrays

This thesis explores planar analogues to several existing fluid-infiltrated microstructured fibre devices. Special attention is given to the application of these planar periodic guiding schemes for refractive index sensing.

The major contribution of this work is the demonstration of fluid tuned discrete diffraction in liquid-core polymer waveguide arrays. To experimentally demonstrate fluid tuned discrete diffraction, a novel planar platform is developed and fabricated based on polymer dry film lamination. The realised liquid-core waveguides are single mode and exhibit symmetric coupling. The rate of discrete diffraction can be thermally tuned. Further, it is theoretically predicted and experimentally demonstrated that if a defect is introduced to the array, tuning of the wavelength or fluid refractive index can cause a transition from light being guided in the defect waveguide to it being coupled off via discrete diffraction. Finally, a new concept is introduced and modelled which enables fluid tuned Bragg guidance using a reverse symmetry air cladding defect waveguide.

In summary, three fluid tuned periodic guiding schemes on planar platforms have been designed and modelled to provide a planar counterpart to exiting infiltrated periodic fibre-based platforms. The first two of these platforms have been experimentally realised and tested. The latter two platforms have been designed to perform refractive index sensing of water based solutions suggesting some significant opportunities for enhanced sensitivity due to periodicity and high fluid field interaction with possible applications in biosensing.