Investigation of stimulated Brillouin scattering in As2S3 photonic crystal fibers at the mid-infrared waveband

Stimulated Brillouin scattering in As2S3 photonic crystal fibers was investigated at wavelengths of 2 mu m to 6 mu m by the finite element method. The numerical results indicate that the proposed photonic crystal fiber can maintain single-mode operation when the air filling factor is less than 0.6. The Brillouin frequency shift is mainly influenced by the pump wavelength and fiber structure. The Brillouin frequency shift de-creases by 4.16 GHz when the pump wavelength is increased from 2 mu m to 6 mu m, while the Brillouin fre-quency shift changes by the order of megahertz when the rate of air filling increases from 0.5 to 0.6. The FWHM of the Brillouin gain spectrum depends on the phonon lifetime, and the FWHM of the Brillouin gain spectrum is nine times wider at a pump wavelength of 2 mu m than that at a pump wavelength of 6 mu m. The maximum Brillouin gain of the proposed fibers with air filling fractions of 0.5 and 0.6 are 2.413x10-10 m/W and 2.429x10-10 m/W, respectively. The Brillouin threshold is positively correlated with the pump wavelength for the same effective fiber length, and is 27.8% and 19.6% larger at a pump wavelength of 6 mu m than that at 2 mu m with air fill factors of 0.5 and 0.6, respectively. The numerical results are of great signific-ance for the design and fabrication of optical devices or optical sensors based on the proposed fibers in the mid-infrared band.