Abstract
The concept of microstructured and photonic band gap fibres opens a wide range of flexibility to introduce specific functionality in fibre light guiding properties and to adapt optical fibres to specific applications. In addition to flexible structural parameters, the use of specific material properties further increases the design freedom in optical fibres. In order to demonstrate the wide functional capabilities of such fibres, we have investigated different index guiding and photonic band gap fibres made from pure and modified silica and from non‐silica materials. The main interest in the use of different materials than the well‐known high‐purity silica is to utilize special optical properties such as high nonlinearity, specific dispersion or extended infrared transmission windows. A main challenge for such unconventional materials is to transfer the excellent properties of silica‐based photonic crystal fibres, like low spectral loss or good durability, to the modified or non‐silica materials. The preparation of modified silica‐based photonic crystal fibres was implemented by the MCVD doping process or by the use of high‐melting lanthanium or lead silicate special glasses. Highly germanium‐doped silica rods were used for the preparation of index guiding and for band gap guiding fibres. The prepared fibres were investigated in their mode propagation properties and compared to model calculations. Application examples are presented for spectral fibre sensing and for supercontinuum generation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)