Fabrication of novel integrated components for next-generation optical networks using the femtosecond-laser direct-write technique

By tightly focussing a femtosecond laser beam inside the bulk of a transparent dielectric, a highly localised and permanent change of the material´s refractive index can be induced. This provides the basis for the rapid fabrication of fully integrated 3D photonic structures and devices that are not only compact and lightweight but also inherently robust since they are embedded within the bulk material. In this paper, we report on our capabilities to fabricate novel and unique components that will find applications in next-generation optical communication networks: Mode-selective waveguide couplers enable the use of multimode-optical fibres in ultrahigh-bandwidth mode-division multiplexing systems whereas thermal poling can be employed to create large second-order optical nonlinearities for applications such as second-harmonic generation or electro-optic modulation and switching.