Fabrication and evaluation of sapphire fiber cladding via magnesium aluminate spinel sol-gel based approaches

摘要

The absence of an effective and stable cladding has been a major hurdle in utilizing single crystal fibers for harshenvironment sensing applications despite the promise of sapphire for temperatures as high as 1800°C. This work discussesthe development of a high temperature cladding for sapphire fibers using wet chemical methods. Magnesium aluminatespinel has been chosen as the material for the cladding as it has a lower refractive index compared to sapphire and doesnot undergo significant interdiffusion with sapphire at temperatures below approximately 1200°C. Different sol-gel basedapproaches have been pursued to develop polycrystalline cladding layers with thicknesses greater than a micron, asrequired to ensure adequate confinement of the guided electromagnetic radiation within the fiber core. For sapphire fibers,high temperature stability of the cladded fibers as well as the effect of the cladding layer on optical characteristics underdifferent application relevant gas environments at elevated temperatures has been investigated.