Fabrication of silica hollow core photonic crystal fibres for Er:YAG surgical applications

In this work we present the fabrication of silica hollow core photonic crystal fibres (HC-PCF) with guidance at 2.94μm. As light is confined inside the hollow core with a very small overlap of the guided E-M wave with the fibre material, the high intrinsic loss of silica at these mid-infrared wavelengths can be overcome. The band gap effect is achieved by a periodic structure made out of air and fused silica. As silica is bio-inert, chemically stable and mechanically robust, these fibres have potential advantages over other multi-component, non-silica optical fibres designed to guide in this wavelength regime. These fibres have a relatively small diameter, low bend sensitivity and single-mode like guidance which are ideal conditions for delivering laser light down a highly flexible fibre. Consequently they provide a potential alternative to existing surgical laser delivery methods such as articulated arms and lend themselves to endoscopy and other minimally invasive surgical procedures. In particular, we present the characterisation and performance of these fibres at 2.94 μm, the wavelength of an Er:YAG laser. This laser is widely used in surgery since the wavelength overlaps with an absorption band of water which results in clean, non-cauterised cuts. However, the practical implementation of these types of fibres for surgical applications is a significant challenge. Therefore we also report on progress made in developing hermetically sealed end tips for these hollow core fibres to avoid contamination. This work ultimately prepares the route towards a robust, practical delivery system for this wavelength.