Optical microfabrication of tapers in low-loss chalcogenide fibers

We demonstrate the use of photoinduced fluidity in low-loss chalcogenide fibers for producing tapers with fine control of the diameter and geometry. The tapers produced this way act as sensing zones along chalcogenide glass fibers used for evanescent wave spectroscopy. The optical microfabrication method consists in irradiating the chalcogenide fiber with sub-bandgap laser light under a tensile stress. The resulting athermal photoinduced fluidity permits to produce tapers with good control over the geometry without altering the optical properties of the fiber. Gains in detection sensitivity greater than 1 order of magnitude are measured using these tapers.