Brillouin scattering in hollow-core fibers filled with mixed gas

Brillouin scattering in gas-filled hollow-core fibers (HCFs) is significantly enhanced by the strong light-gas interaction and the tunability of gas properties by the hollow-core structure. However, the behavior of Brillouin scattering in HCFs filled with mixed gas remains unexplored. In this work, we present the first, to the best of our knowledge, investigation of backward Brillouin scattering in HCF waveguides filled with mixed gas. We examine its dependence on pressure, temperature, and gas composition, developing a theoretical model that aligns well with experimental results. Furthermore, we demonstrate that the Brillouin spectrum can be tuned via gas concentration and pressure, offering new possibilities for controlling Brillouin interactions in gas-filled waveguides.