Photonic Bandgap Guiding in an Opal Clad Fibre

Self-assembly is a promising technique for fabricating three-dimensional photonic crystals due to the relative simplicity of the fabrication process and the ability of the finished structure to possess a full photonic bandgap. Self-assembly involves taking a sample of uniformly sized microspheres and providing conditions in which they will arrange themselves periodically. Self-assembled photonic crystals are often called opals due to their similarities to the natural gem stone. It has been shown that self-assembled photonic crystals can be grown around curved surfaces, provided that the curvature of the surface is much larger than that of the spheres. Kitaev et al., (2005) were able to grow an opal structure around a silica optical fibre and show a uniform bandgap at all radial angles with respect to the core. This was proposed as being a prelude for new type photonic bandgap fibre, though the paper did not include any demonstration of this effect. For the first time, we have demonstrated bandgap guiding in the cladding of an opal encapsulated fibre, proving that the concept can be realised.