Large Brillouin gain in Germania-doped core optical fibers up to a 98  mol% doping level

Germanosilicate glasses are substantial materials in fiber optic technology that have allowed the control of optical properties such as numerical aperture, photosensitivity, dispersion, nonlinearity, and transparency toward mid-infrared. Here, we investigate stimulated Brillouin scattering in single-mode germanosilicate core fibers with increasing GeO₂ content from 3.6 mol% up to 98 mol%. Our results reveal a wide Brillouin frequency shift tunability over more than 3 GHz with a strong decrease down to 7.7 GHz at high GeO₂ content owing to the low acoustic velocity, while the Brillouin linewidth significantly broadens up to 100 MHz beyond 50 mol% of GeO₂ content. In addition, large Brillouin gain up to 6.5 times larger than in standard silica fibers is also reported by means of a pump-probe experiment.