Direct femtosecond laser writing of low-loss waveguides in chalcogenide glasses for mid-infrared applications

Direct femtosecond laser writing technique is now widely used in particular in glass, to produce both passive and active photonic devices. This technique offers a real scientific opportunity to generate three-dimensional optical components. The chalcogenide glasses are of great interest since they possess a transparency window from the visible up to the mid-infrared range. Moreover, they also have high optical non-linearity and high photosensitivity that facilitate the inscription of permanent refractive index modification. In this presentation, an original method based on both the filamentation phenomenon and a point-by-point technique will be described. The written waveguide is of multicore type and consists in parallel channels of positive Delta n placed parallel to each other on a hexagonal or a circular mesh. The performances in terms of optical losses at both 1.55 mu m and 4.55 mu m measured in such photowritten buried infrared waveguide are very competitive. This writing technique is particularly suitable for the design of single mode waveguide for wavelengths ranging from the visible up to the mid-infrared since the geometry of the inscription and the amplitude of the refractive index modification can be easily adapted. This also paves the way for the fabrication of advanced mid-infrared optical components such as Y-splitters.