Novel etching process based on molten salts for optical fiber components

Optical fiber components have the potential of enabling interconnections in compact systems because they provide reliable and efficient manipulation of light in application fields such as telecommunication, sensing and high power. A variety of glasses and fiber components including tapers, tips, bundles and couplers are typically fabricated using hydrofluoric acidbased etching processes. However, such a standard approach has some limitations related to the generation of surface defects (e.g., roughness and microcracks), poor process control and high chemical disposal costs. We propose an innovative glass etching process based on molten salts that will overcome these limitations. Molten salts can be thermally activated to etch glass materials with high precision. Initial plant development and industrial manufacturing capabilities are demonstrated on a modular etching system through a research collaboration. This system also has the advantage of managing a set of fibers simultaneously with an automatic process control. First results of etched glasses and especially, biconical fiber tapers show extremely smooth surfaces, good homogeneity, high reproducibility and potential scalability for further processing of fiber couplers. With respect to the fabrication tolerances, a value of ± 1 μm over a length of 10 mm has been found for the case of etched multimode tapers. The use of molten salts as an etching tool can be extended to economically create microstructures in glass panels for optical or fluidic purposes.