Elaboration of photonic crystal fibers for telecom and mid infrared wavelengths

Chalcogenide glasses are known for their large transparency in the mid infrared and their high refractive index (>2). They present also a high non linear coefficient (n₂), 100 to 1000 times larger than for silica, depending on the composition. An original way to obtain single-mode fibers is to design microstructured optical fibers (MOFs). In addition, these fibers present unique optical properties thanks to the high degree of freedom fro the design of their geometrical structure. A classical method to realize MOFs is the stack and draw technique. In order to avoid the interfaces problems observed in chalcogenide glasses, we have developed a new casting method to fabricate the chalcogenide preform. This method permits to obtain optical losses around 1 dB/m at 1.55 μm and 0,3 dB/m in mid IR. Our group has prepared various chalcogenide microstructured fibers working in the IR range in order to associate the non linear properties of these glasses with the original MOF properties. For example, small effective mode area fibers (A_eff <; 10 μm²) have been realized to exacerbate the non linear optical properties for telecom applications such as signal regeneration, and for supercontinuum sources. On the contrary, and military applications in the 3 - 5 μm and the 8 - 12 μm windows, large effective mode area and single mode fibers have also been designed to permit the propagation of high power Gaussian laser beams.