Comparative study on methods to structure sapphire

Ti:sapphire is an attractive material for applications as a tunable or short-pulse laser and as a broadband light source in low-coherence interferometry. We investigated several methods to fabricate rib structures in sapphire that can induce channel waveguiding in Ti:sapphire planar waveguides. These methods include direct laser ablation, reactive ion etching, and ion beam implantation followed by wet chemical etching. With the latter two methods, we fabricated channels with depths of up to 1.5 µm. Reactive ion etching through laser-structured polyimide contact-masks has so far provided the best results in terms of definition and roughness of the etched structures.