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.

微型光学扫描仪的制造进展将受益于微米尺寸的光纤头。光纤尖端的横截面变化通常伴随着更长的锥形区域。本文考虑了在横截面发生变化（横截面突变）区域具有平坦界面的双包层光纤（DCF）横截面的减小。探索了各种方法，例如加热和牵拉，使用氢氟酸（HF）的湿法蚀刻以及在气态下的蚀刻。还确定了光学蚀刻速率及其对蚀刻剂溶液温度的依赖性。光纤随时间线性蚀刻，蚀刻速度取决于蚀刻剂溶液的温度，该温度呈抛物线趋势。横截面变化时表面的平坦度是制造亚毫米尺寸扫描仪时的一个有趣参数，在该扫描仪中，光透射过DCF的纤芯，反射光则通过同一根光纤的内包层收集，反之亦然。在使用上述技术开发的不同纤维样品之间，对界面处的表面平整度进行了比较。这项研究表明，通过阻止蚀刻剂溶液沿纤维的毛细上升进行的湿法化学蚀刻，在传输至目标样品的光强度和通过蚀刻包层界面收集的反射光方面，比加热和拉动技术更具优势。