Femtosecond laser direct-written microstructured waveguides in passive as well as in novel active glasses

In recent years, the femtosecond laser direct write technique has evolved into a standard technique for the inscription of optical waveguides in glasses. However, due to very slow process speeds and limited 3D-capabilities, this method was restricted to the fabrication of relatively simple structures so far. In this paper we demonstrate how MHz repetition rate chirped-pulse oscillators can be utilised to overcome those limitations, enabling the realisation of complex direct-written microstructured waveguides. We present our results in fabricating ARROW (anti-resonant reflecting optical waveguide) structures in bulk glasses as well as depressed-cladding waveguides in novel fluoride glasses doped with rare-earth ions like thulium and holmium.