The feasibility of chalcogenide rib waveguides working at λ = 10.6µm has been demonstrated. The waveguides comprised a several microns thick Te 2 As 3 Se 5 film deposited by thermal evaporation on a polished As 2 S 3 glass substrate and further etched by physical etching in Ar or CF 4 /O 2 atmosphere. Output images at 10.6µm and some propagation losses roughly estimated at 10dB/cm proved that the obtained structures behaved as channel waveguides with a good lateral confinement of the light. The work opens the doors to the realisation of components able to work in the mid and thermal infrared up to 20 µm and even more. TextThe development of single-mode integrated optics components being able to work in the whole range from 1 to 20 microns is of major interest for specific applications related to detection in the mid and thermal-infrared spectral domain : the detection and identification of pollutant gases for environmental control or the direct detection of exoplanetary systems (ESA Darwin Mission [1]), for example. To date, single-mode integrated optics is limited to the near infrared windows H [1.50 -1.80 µm] and K [2.01 -2.42 µm] due to the silica transmission window. One of the promising possibilities to extend the integrated optics concept to the mid-infrared is to use chalcogenide glasses which transparency in the infrared is well-known. Some channel waveguides mainly based on arsenic sulphide As 2 S 3 or arsenic selenide As 2 Se 3 were already realised [2, 3 for example]. In reference [2], rib waveguides made by a physical or reactive ion etching of As 2 S 3 were optically characterised at λ = 1.5 microns. In reference [3] channel waveguides were obtained by direct laser writing of the As 2 Se 3 core layer deposited on an As 2 S 3 cladding layer and were characterised at λ = 8.5 microns. In both examples, the substrates were crystalline silicon substrates (Si/SiO 2 ) and the working domain of the structures was limited at 12 microns, due to the opacity of As 2 S 3 at longer wavelengths. In order to extend the working domain of such waveguides, the only way is the replacement of the sulphide and selenide films by telluride ones. The number of papers dealing with telluride glasses in bulk form has been growing up in the past few years [6-8] but 2 only a few of them concern films [8][9][10]. Moreover in previous works on telluride films, the film thickness was lower than 1 micron [8][9][10] while the film thickness will have to be typically from 4 to 15 microns for use in the mid-IR. In fact, the further the waveguides will be used in the IR, the thicker the film will have to be. For similar reasons, the films will have to be etched on variable depths, typically from 1 to 10 microns. These dimensions (film thickness and rib depth) are much bigger than the ones usually used for the telecommunication wavelengths and previous tests to reach such characteristics are scarce in the literature [2;11].The present work was dedicated to demonstrate the feasibility of channel waveguides based on telluride films...

The feasibility of all-telluride integrated optics devices based on waveguides presenting a single-mode behavior in the spectral range (10-20 μm) is demonstrated. These waveguides are constituted of a several micrometer thick Te(82)Ge(18) film deposited onto a Te(75)Ge(15)Ga(10) bulk glass substrate by thermal coevaporation and further etched by reactive ion etching under the CHF(3)/O(2)/Ar atmosphere. The obtained structures were proven to behave as channel waveguides with a good single-mode transmission over the whole spectral range. These results allowed validating our technological solution for the fabrication of integrated optics modal filters for spatial interferometry.

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