Influence of optical mode polarization state on the Brillouin gain spectrum in optical microfibers

During the stimulated Brillouin scattering (SBS) process, when the two HE11 modes in the pump light and scattered light have different polarization states, between which is an angle theta, the Brillouin gain spectrum characteristics in a microfiber are studied in detail. The difference of theta directly changes the generated optical force distribution. When 0 <= theta <= pi/2, for the TR0n acoustic mode in forward SBS and the L-0n acoustic mode in backward SBS, the corresponding Brillouin gain values have a clear cosine-like functional relationship with theta. Considering the change of optical force, the TR0n and L-0n acoustic modes with symmetrical displacement distributions of center circles are the key features to realize the change of gain with theta. The characteristics of gain value with theta may provide interesting theoretical enlightenment for Brillouin applications involving angles, such as Brillouin sensors and acousto-optic modulators. (C) 2022 Optica Publishing Group