Design of Silicon Phoxonic Crystal Waveguides for Slow Light Enhanced Forward Stimulated Brillouin Scattering

We propose and design the silicon phoxonic crystal waveguides to achieve forward stimulated Brillouin scattering (FSBS). The waveguides with honeycomb-lattice structure are able to support the photonic and phononic band gaps simultaneously. By the optimized design, the corresponding optical and acoustic defect modes are tightly confined in the line defect to enhance acousto-optic coupling, resulting in the intramode and intermode FSBS. The three-dimensional (3D) full-vectorial theoretical formulation is applied to analyze the influences of structural parameters on FSBS gain. By the coupled-mode equations, we explore the FSBS process taking into account the slow light enhanced factor, two-photon and free-carrier absorptions in the slow-light phoxonic crystal waveguide. The results indicate that 18 dB Stokes amplification is obtained with 100 mW pump power in a short waveguide length of 200 μm. Such approach enables the realization of on-chip FSBS with CMOS technologies.