Fabrication of periodic, resonant features in optical fibres using a CO2 laser micro-tapering system

We report on novel devices fabricated using an optical fibre micro-tapering facility based on a CO₂ laser and high precision translation stages, all of which are computer controlled. The use of a laser to heat the fibre is advantageous over standard flame-tapering systems as it allows greater control over the tapering parameters, namely the size of the irradiated zone, the heating rate and the exposure time. Mounting the fibre on computercontrolled stages gives programmable dynamic control over the fibre tension, as well as the ability to control the position of the tapered section with an accuracy of ±0.5 μm. Using this system, taper regions as short as 150 μm were achieved with a fibre diameter reduction of 50%. Furthermore, periodically tapered fibres and fused tapered microcouplers have been fabricated using this method. Fibres perturbed in this fashion are useful in furthering our understanding of cladding mode interactions and radiation dynamics in optical structures with a non-uniform profile.