Optical nanofibers: technology and transmission properties

Optical nanofibers can be prepared as long fiber tapers by remelting and redrawing of existing light guiding fibers down to much smaller diameters than common 125µm standard fibers. We discuss the fabrication process of optical nanofibers down to diameters of a few hundred nanometers. The fiber is heated indirectly in an Al2O3-tube, which is irradiated by two sides with a CO2-laser-beam. An oscillating motion of the fiber in the locally heated tube allows the generation of nanofibers with a constant diameter for several millimeters length. Such nanofibers can be investigated concerning their transmission properties and their possible applications such as e.g. evanescent field sensor systems or for nonlinear optics. We analyzed the evolution of the transmission properties during the tapering process of a standard single mode fiber. Depending on the actual diameter, regions with different light guiding properties can be distinguished.