High efficiency of Brillouin scattering behavior in single-mode Ge-As-Se-Te fibers at 2 μm

The Brillouin characteristics of step-index Ge-As-Se-Te (GAST) fibers at 2 mu m are designed and simulated on the basis of optical and acoustic properties. The refractive indexes of Ge20As20Se45Te15 glass and Ge20As20Se43Te17 glass serving as fiber core and cladding are 3.20 and 3.18 at 2 mu m, and their acoustic velocities are 2200 m/s and 2300 m/s, respectively. Numerical results indicate that the stimulated Brillouin scattering (SBS) efficiency is 248 m 1 center dot W 1, and the Brillouin threshold power is 66 mW when the core diameter of the 2-m-long GAST fiber is 4 mu m at 2- mu m wavelength. The optic-acoustic coupling factor, the Brillouin frequency shift, and the Brillouin gain coefficient are 0.98, 7.02 GHz, and 3.81x10(-9) m/W, respectively. The SBS effect of GAST fibers simulated for the first time provides a new promising approach to selecting gain medium based on 2- mu m-wavelength fiber laser.