Composite three-layer potassium and silver halide fibre for the mid-IR range

We report for the first time the possibility of co-extrusion of silver and potassium halide crystals to produce double-clad polycrystalline IR fibres. This combination allows the disadvantages inherent in each of the crystals separately to be overcome. The resulting fibres have stable long-term transmission and can be used to transmit CO₂ laser radiation. The loss in the fibre at a wavelength of 10.6 μm constitutes 0.75 dB m^-1.