Photo-Writable Sulfide Glasses Used to Fabricate Core-Clad Fiber Doped with Pr${}^{3+}$ for Mid-IR Luminescence

With the ultimate goal of developing rare-earth doped chalcogenide fiber fabrication for sensing, amplification, and laser applications, a core/clad germanium-gallium sulfide fiber doped with Pr${}^{3+}$ has been fabricated. The compositions of the core and the clad were selected to ensure the positive $\mathrm{\Delta }$n by adding CdI${}_2$ and CsCl, respectively, in the GeS${}_2$ -Ga${}_2$S${}_3$ matrix. The choice of these compositions was also justified from experimental parameters, including characteristic temperatures and viscosity. Moreover, the permanent photo writability of the sulfide glass family by a femtosecond laser is investigated from the perspective of Bragg grating photo-inscription. Structural investigations by Raman spectroscopy are presented and the effect of the Pr${}^{3+}$ rare-earth ion on the structure is underlined. Finally, the emission of the step-index fiber, made by the rod-in-tube technique between 3.1 $\mu$m and 5.5 $\mu$m (by pumping at 1.55 $\mu$m), is demonstrated.