Role of microstructure on guided acoustic wave Brillouin scattering in photonic crystal fibers
Résumé
We study guided acoustic wave Brillouin scattering (GAWBS) in several photonic crystal fibers (PCF) with different kind of air-hole microstructure and we show this effect is enhanced only for a few acoustic phonons. The results of our numerical simulations based on a finite element method reveal that these acosuti waves emitted in the GHz range are indeed trapped within the air-hole microstructure, in good agreement with experimental observations. The periodic wavelength-scale air-hole microstructure of solid-core PCFs can indeed drastically alter the transverse elastic waves distribution and therefore forward Brillouin scattering compared to what is commonly observed in conventional all-silica fibers. We show additionnally that the elasto-optic diffraction coefficient and the transverse acousto-optic field overlap are maximum for these acoustic waves. For the most intense GAWBS modes, we investigate the scattering efficiency and temperature dependence of the fundamental phonon frequency for sensing applications.