Stimulated Brillouin Scattering Gain of Waveguides Calculated with Acoustic Perturbation Method

Stimulated Brillouin Scattering (SBS) is a phenomenon of energy transfer from an optical pump beam to longer wavelengths of light through its interaction with the medium via acoustic phonons. Previous studies have reported a calculation of the SBS gain based on the optical force approach, where the gain is not only affected by the classical paradigm of intrinsic material's nonlinear effects in the form of electrostriction but also due to radiation pressure. In this work, the acoustic perturbation approach is applied in analyzing the optical and mechanical response of the waveguide, wherein calculating the scattering process, the changes of the waveguide structure due to photoelasticity (PE), termed Moving Boundary (MB), are considered. This acoustic perturbation method avoids uncertainties related to optical force contributions. To validate its applicability, the present method is used to calculate the SBS gain of various waveguide structures, namely an unsuspended Silicon nano-waveguide, ridge Lithium Niobate (LiNBO3) nano-waveguide on Sapphire (Al2O3) substrate and buried Arsenic trisulfide (As2S3) in Silicon dioxide (SiO2). The forward and backward SBS gain obtained using the present method of acoustic perturbation are similar to the reported values obtained from other methods of calculation as well as experiments.