Highly precise and flexible manufacturing of integrated optical structures in fused silica using selective laser etching

Abstract

Selective laser etching (SLE) enables highly precise 3-dimensional structuring of glasses with a resolution as low a few µm. Two main process steps are necessary for this technique. First, the previously created design is written inside the glass by using fs-laser radiation. Subsequently, the glass is placed in acid or a lye, to etch the laser-modified area. Hereby, the required substance for the post-processing step depends on the used glass. In our work, we investigated the structuring of fused silica with subsequent etching with KOH in detail. We studied the influence of different writing parameters such as laser power, repetition rate, polarization, stage movement speed and hatching distance towards an optimized surface roughness which is crucial for optical applications. The technology is not limited to the structuring of flat glass substrates, but applicable to fibers, waveguides or more complex 3D structures as well. Also hollow-core fibers have been processed to create an inlet and outlet for fluids and standard glass fibers were etched to realize free access to the fiber core, respectively. Especially the latter process enables a wide field of further applications if e.g. metal organic frameworks will be applied for sensing purposes or further optical structures printed on their surface by using twophoton polymerization processes.