All-telluride waveguides for nulling interferometry in the 6–20 µm spectral range: Fabrication and testing

The feasibility of two types of all-telluride integrated optics devices being able to single-mode guiding of light in the spectral ranges [6 – 11 µm] and [10 – 20 µm], respectively, is demonstrated. The so-called rib waveguides show a several micron thick Te 82 Ge 18 film deposited onto a Te 75 Ge 15 Ga 10 bulk glass substrate by thermal co-evaporation and further etched by reactive ion etching in CHF 3 /O 2 /Ar atmosphere. First, the slab waveguides obtained before etching were highlighted to transmit light in the whole spectral range, from 6 to 20 µm. The etched structures were then proved to behave as channel waveguides with a satisfactory confinement of light. To end, optical losses of about 4 dB·cm −1 and modal filtering with a light rejection efficiency of 6·10 −5 were obtained on a very first sample of the [6 – 11 µm] type. These results allowed validating our technological solution for the fabrication of micro-components for spatial interferometry.