Nanocrystalline CVD Diamond Coatings on Fused Silica Optical Fibres: Optical Properties Study

Seeding and growth processes of thin diamond films on fused silica optical fibres have been investigated. Glass pre-treatment by dip coating in two detonation nanodiamond (DND) seeding media has been studied. The DND suspension in ethyl alcohol and dispersion of DND in dimethyl sulfoxide (DMSO) with polyvinyl alcohol (PVA) were chosen for the seeding purpose. The grain size distribution of nanodiamond particles in both seeding media was kept at the same level (approximately 10-50 nm). After the seeding nanocrystalline diamond films were deposited on the fibres using microwave plasma assisted chemical vapour deposition system. The results of the process were investigated using numerical analysis of scanning electron microscopy images. The molecular structure of diamond has been examined with micro-Raman spectroscopy. Thickness, roughness and optical properties of the nanocrystalline diamond films in VIS-NIR wavelength range were investigated on reference samples using spectroscopic ellipsometry. Light reflection at the fibre end-face for different deposition parameters was also investigated. Proposed seeding method can be further effectively applied for manufacturing of optical fibre sensors. Due to extraordinary properties of diamond, which include high chemical and mechanical resistance, such films are highly desired for optical sensing purposes.