Analysis of Forward Stimulated Brillouin Scattering in Nanoscale SiGe Waveguides by Tailoring Optical Forces

Abstract

We propose and design SiGe strip waveguides and silicon waveguides with SiGe cover layers to tailor optical forces. The forward stimulated Brillouin scattering (FSBS) in these SiGe waveguides are analyzed by considering the effects of SiGe concentration on the optical forces. In the radiation-enhanced configuration, electrostrictive forces can constructively add to or destructively interfere with radiation pressure, depending on the concentration. The silicon waveguides with graded-varying cover layers provide a means of enhancing photon–phonon interaction and rewriting the selection rule of excited acoustic modes. The numerical simulation results indicate that SiGe strip waveguides can realize the largest net Stokes’ amplification up to 10.32 dB. Compared to traditional pure silicon waveguides, the silicon waveguides with graded-varying cover layers have an improvement of about 40% on Brillouin gain and at least 2.5 dB on net Stokes’ amplification. Our proposed SiGe waveguides offer an effective approach to implement flexible FSBS in silicon-based chip.