Photonic crystal fibres (PCFs) have been the focus of increasing scientific and technological interest since the first working example was reported in 1996 (for a review see Science 299 (358-362) 2003). Although superficially similar to a conventional hair-thin glass optical fibre, PCF has a unique microstructure, consisting of an array of microscopic hollow channels running along its entire length. These channels act as optical barriers or scatterers, and suitably arranged can corral light within a central core (either hollow or made of solid glass). PCF can trap light in two different ways: by a modified form of total internal reflection, when the core must have a higher average refractive index than the photonic crystal cladding; and by a two-dimensional photonic bandgap, when the index of the core is uncritical it can be hollow or filled with material. Light can be controlled and transformed in these fibres with unprecedented freedom, allowing for example precision guidance of light in a narrow hollow core (Science 285 (1537-1539) 1999), the creation of highly nonlinear PCFs with accurately controlled dispersion profiles (Nature 424 (511-515) 2003), the design of fibres that guide only one mode at all wavelengths (Optics Letters 22 (961-963) 1997), and the observation of stimulated Raman scattering in hydrogen at threshold powers six orders of magnitude lower than ever seen before in single-pass geometries (Phys. Rev. Lett. 93 (123903) 2004; Nature 434 (488-491) 2005). These are just a few examples of how the PCF concept has ushered in a new and more versatile era of fibre optics, with a multitude of different applications spanning many areas of science.

Philip Russell is Director of the Max-Planck Research Group for Optics, Information & Photonics at the University of Erlangen, Germany. From 1996 to 2005 he founded and led the Photonics & Photonic Materials Group at the University of Bath. He specializes in periodic structures, nonlinear optics, waveguides and their applications. A Fellow of the Optical Society of America, in 2000 he won its Joseph Fraunhofer Award/Robert M. Burley Prize for the invention of photonic crystal fibre. In 2005 he was elected Fellow of the Royal Society and received the Thomas Young Prize of the UK Institute of Physics and the Köerber Prize for European Science.