Single-mode integrated optics is an increasingly employed technology in interferometric instruments to reach high-accuracy visibility and closure phases measurements. Here, we address the progress achieved in the area of mid-infrared integrated optics beam combiners beyond 2.5 µm fabricated in MIR chalcogenide glasses by ultrafast laser inscription. Thanks to the synergistic cooperation between the Universities of Cologne and Macquarie, we fabricated optimized asymmetric and multimode interference beam combiners and tested them around 4 µm. In contrast to our earlier works, we also focused on the high-contrast capabilities of these devices and measured levels of null depth. This may become relevant for future projects such as Hi5/VLTI or the space mission LIFE.
