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

TL;DR

This paper reports the fabrication and characterization of Pr$^{3+}$-doped germanium-gallium sulfide core-clad fibers with photo-writable properties, aiming at mid-IR sensing, amplification, and laser applications.

Contribution

It introduces a novel Pr$^{3+}$-doped sulfide glass fiber with photo-inscription capabilities and demonstrates its mid-IR luminescence emission, advancing rare-earth doped chalcogenide fiber technology.

Findings

Successful fabrication of Pr$^{3+}$-doped sulfide glass fiber.

Demonstration of mid-IR emission between 3.1 and 5.5 μm.

Evidence of photo-writability via femtosecond laser Bragg grating inscription.

Abstract

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 $\Delta$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.