Stimulated Brillouin scattering in high-birefringence elliptical-core As₂Se₃-PMMA microfibers

In this Letter, we design and fabricate elliptical-core (ECORE) chalcogenide-polymethyl methacrylate (As₂Se₃-PMMA) microfibers to explore the birefringence impact on stimulated Brillouin scattering. Numerical simulations based on the finite-element method and elastodynamic equation are utilized to calculate the phase and group birefringence and Brillouin gain spectra of the fundamental mode in three ECORE As₂Se₃-PMMA microfibers at different core diameters. Experimentally measured and numerically calculated results show that as the core diameter of the minor axis of an ECORE microfiber with a ratio of 1.108 is reduced from 1.50 µm to 0.87 µm, a high group birefringence of ∼10^-3 to ∼10^-2 and a large Brillouin frequency shift difference of ∼6MHz to ∼30MHz are achieved, while the Brillouin gain spectra are broadened significantly from ∼70MHz to ∼140MHz. The high-birefringence ECORE As₂Se₃-PMMA microfiber is important for Brillouin sensing due to the tailorable high birefringence and ultrahigh nonlinearity.