Harnessing Intra‐Mode Forward Stimulated Brillouin Scattering in Few‐Mode Optical Fibers

Abstract Forward stimulated Brillouin scattering (FSBS) in optical fibers has gained attention in both fundamental physics and practical applications. While FSBS involving the fundamental optical mode and guided transverse acoustic waves has been studied in different optical fibers, its behavior in few‐mode fibers and the potential for tailoring the FSBS gain spectrum through optical wave distributions remain largely unexplored. Here, the first analysis of intra‐mode FSBS is presented in few‐mode optical fibers and demonstrate the possibility of harnessing its spectral profile using high‐order optical modes. Experimental results, supported by a theoretical analysis and full vectorial finite element method simulations, demonstrate that selecting specific optical modes in few‐mode optical fibers enhances overlap between high‐order acoustic modes and optical forces, significantly boosting the amplitude of high‐order acoustic resonances. This approach offers a practical and previously unexplored mechanism to manipulate FSBS photon‐phonon interactions, creating new opportunities for studying FSBS fundamentals and paving the way for developing novel optomechanical devices.