In recent years, a growing interest has settled for optical materials and fibers for the mid infrared (mid-IR) region. This interest originates from societal needs for health and environment for instance, and also from demand for defence applications. Indeed, the mid-IR spectral region contains the atmospheric transparent windows (3-5 μm) and (8-12 μm) where thermal imaging (military and civilian) can take place. The elaboration of chalcogenide microstructured optical fibers (MOFs) permits to combine the mid infrared transmission of chalcogenide glasses up to 18 μm to the unique optical properties of MOFs thanks to the high degree of freedom in the design of their geometrical structure. In this context, additive manufacturing of glass materials appears as an attractive technique to achieve more elaborate designs that can hardly be obtain using more common methods such as the stack-and-draw or molding. Taking advantages of the specific physical properties of chalcogenide glasses such as low Tg and extrusion temperature, we have shown that chalcogenide preforms can be rapidly obtained by fused deposition modeling (FDM) using a customized RepRap-style 3D printed fed with chalcogenide glass rods. Such as-prepared preforms can be drawn into chalcogenide optical fibers. Those early-stage results open a new way for the elaboration of chalcogenide MOFs.
Alternative way of synthesis for high refractive index tellurides based glasses has been experimented, in addition to low temperature Spark Plasma Sintering. The composition tested, Ge25Se10Te65, has been chose in the Ge-Se-Te system and characterized. Its index refractive index of 3.12 and overall optical, thermal and mechanical properties makes it the perfect candidate for IR application. However, due to its relative instability regarding crystallization, formation of GeTe crystals occurs during mechanical alloying using raw elements. Transparency has not been achieved in the sintered samples using this powder, as the crystallization rate is accelerated by the pressure during the process. In parallel, glass samples synthesized by melt-quenching have been used to determine optimal sintering parameters for this composition. The main issue met during those tests has been the carbon contamination, reducing overall transparency of the samples through scatterings. As such, it has been shown that the critical parameter to consider to limiting this pollution is the powder granulometry, needing to be above 100μm for optimal performance. This shows the potential for this method to produce high refractive index IR optics, using even unstable glasses.
For several years, chalcogenide glasses have been studied as good candidates for numerous applications in the midinfrared region. Indeed, these glasses are transparent from 1 to 20 μm (depending on the composition), a mid- IR windows well-suited for sensing molecules whose optical signatures are located in the 2-16 μm range. In addition, thanks to appropriate thermal properties, chalcogenide glasses can be drawn into fibers, including microstructured optical fibers. In this work, a new method based on 3D-printing process is investigated to produce hollow chalcogenide glass preforms, which are then drawn into hollow-core fibers. The transmission of the “printed” hollow-core fiber has been measured and compared to the initial glass. A significant, but still manageable, increase by a factor of 2.5 is observed. This works opens a promising way for the fabrication of chalcogenide MOFs, more particularly for the elaboration of hollow core fibers.
The elaboration of chalcogenide microstructured optical fibers (MOFs) permits to combine the mid infrared transmission of chalcogenide glasses up to 18 µm to the unique optical properties of MOFs thanks to the high degree of freedom in the design of their geometrical structure. In this context, we have shown that chalcogenide preforms can be obtained by an original additive manufacturing process We have also shown that these preforms can be drawn into chalcogenide optical fibers. Those early-stage results open a new way for the elaboration of chalcogenide MOFs with more elaborate designs.
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