Optical properties of high numerical aperture silica fibres coated with amorphous perfluorinated polymers

Samples of optical silica fibres with a reflective cladding made of amorphous perfluorinated copolymers of perfluoro-2,2-dimethyl-1,3-dioxol and perfluoro(propyl vinyl ether) are fabricated. The copolymers have high optical transparency and an ultralow refractive index n = 1.293 – 1.314 in the visible and near-IR wavelength ranges, which makes it possible to form optical fibres with a high numerical aperture. The polymer cladding is deposited on the silica light-guiding core of the fibre by a die method both from melts and from copolymer solutions. The optical losses, aperture and scattering properties of the formed silica-polymer fibres are studied. They are compared with the optical properties of fibres with light-reflecting claddings made of organosilicon elastomers and polycrystalline fluoropolymers.