'Designer glasses' for Ultrafast Laser-Inscribed low-loss optical waveguides

Integrated optics are the engine of the Internet and are driving innovation in life science, quantum computing as well as astronomical instrumentation. Traditionally integrated optics are fabricated using lithography, leveraging mass-fabrication technology from electronic integrated circuits. Yet the desire for advanced manufacturing has brough about great interest in rapid prototyping. To rapid prototype integrated optical circuits, Ultrafast Laser Inscription (ULI) is the most prevalent technology, whereby a laser is focused into a glass substrate causing a permanent refractive index modification. High throughput inscription at 10s of millimetres of waveguide per second can be achieved using ULI when operating in a regime known as cumulative heating. Waveguides are formed via ion migration causing a localised compositional change within the glass substrate that in turn alters the refractive index. Therefore, the composition of the glass substrate is an essential factor to form low loss waveguides. The most widely used substrates are alkaline-earth boro-aluminosilicate glasses developed for the flat-panel display industry. These glasses are of technical nature and hence they do not match the quality, homogeneity, and purity of optical glass, which are essential properties for guided-wave applications.