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 μm are designed and simulated on the basis of optical and acoustic properties. The refractive indexes of Ge ₂₀As ₂₀Se ₄₅Te ₁₅ glass and Ge ₂₀As ₂₀Se ₄₃Te ₁₇ glass serving as fiber core and cladding are 3.20 and 3.18 at 2 μm, 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⋅W ⁻¹, and the Brillouin threshold power is 66 mW when the core diameter of the 2-m-long GAST fiber is 4 μm at 2-μm wavelength. The optic–acoustic coupling factor, the Brillouin frequency shift, and the Brillouin gain coefficient are 0.98, 7.02 GHz, and 3.81 × 10 ⁻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-μm-wavelength fiber laser.