Advancements in fabrication of miniaturized optical scanners would benefit from micrometer sized optical fiber tips. The change in the cross section of an optical fiber tip is often accompanied with the presence of a longer tapered area. The reduction of the cross section of double clad optical fibers (DCFs) with a flat interface surface at the region where a change in the cross section takes place (with an abrupt change in the cross section) is considered in this paper. Various methods such as heating and pulling, wet etching using hydrofluoric acid (HF), and etching in a vaporous state were explored. The optical etching rate and its dependence on the temperature of the etchant solution were also determined. Optical fibers etch linearly with time, and the etching speed is dependent on the temperature of the etchant solution which shows a parabolic trend. The flatness of the surface at the cross section change is an interesting parameter in the fabrication of submillimeter sized scanners where the light is transmitted through the core of the DCF, and reflected light is collected through the inner cladding of the same fiber, or vice versa. The surface flatness at the interface was compared among different fiber samples developed using the aforementioned techniques. This research illustrates that the wet chemical etching performed by blocking the capillary rising of etchant solution along the fiber provided advantages over the heating and pulling technique in terms of light intensity transmitted to the target sample and the reflected light collected through the interface of etched cladding.
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