Nonlinear topological routing enabled by stimulated Brillouin scattering

Stimulated Brillouin scattering (SBS) plays a vital role in optics and optoelectronics. Here, we demonstrate an on-chip directional coupling scheme based on SBS in a two-dimensional photonic crystal exhibiting topologically protected edge states. Our design achieves an SBS gain of G_b/Q_m=2.29W⁻¹⋅m⁻¹ at 10.01 GHz, with an estimated excitation threshold of 120 mW. The calculated coherent SBS coupling remains within 3 dB of its maximum phase-matched value over a full phonon-frequency deviation range of approximately 0.75 GHz. In addition, the device maintains functional directional coupling performance under substantial structural disorder, this robustness concerns the optical edge-state transport and port-mapping response. These findings highlight the potential of SBS-induced nonlinear interactions to realize arbitrary directional emission across three output ports. The proposed compact and resilient device opens avenues for integration into future photonic integrated circuits, particularly optical routing such as optical switches, and reconfigurable optical logic gates.