Reduction of thermally induced waveguide degradation in the laser glass deposition of optical fibers through melt pool adaption

With the laser glass deposition, optical quartz glass fibers with a core-cladding structure are welded on fused silica chips for all-glass on-chip light-guiding systems. However, previous welding experiments resulted in a degradation of the transmission properties of the fibers [F. Spengler, Procedia CRIP, 124, 484 (2024)]. In this work, the beam path of the CO2 laser is modified to improve the transmission of the on-chip welded fibers and to maintain their single-mode properties. Rather than being guided directly onto the fiber from above, the laser beam is directed between the fiber and the substrate. The fiber is continuously placed in the created melt pool of the substrate, which enables a material bond with reduced thermal impact on the fiber core. The influence of process parameters, such as the power density and the wavefront curvature, on the optical transmission properties of welded fibers is systematically analyzed. Compared to previous processes, a 50% reduction in optical transmission losses can be observed. In the same process environment, an innovative laser-based cleaving process is being developed to create cleaves with end facet angles between 0° and 12°, enabling efficient and versatile coupling strategies and precise on-chip integration of discrete optical components through microassembly strategies such as pick and place.