Acoustic wave propagation along cladded fibers of cubic crystalsymmetry

摘要

An approximate method is proposed to analyze the acoustic wavenpropagation characteristics in nonpiezoelectric cladded fibers of cubicncrystal symmetry. The fiber axis coincides with the crystalline Z axis.nThis approximate method utilizes coupled mode equations and the exactnsolutions for the corresponding cladded isotropic fiber are used as thenapproximation base. We concentrate our analysis on cubic fibers withnweak anisotropy where the first order approximation obtained from thencoupled mode equations can provide accurate results. Dispersion curvesnof a few lower order flexural, torsional and radial-axial modes in suchna fiber with infinite cladding are presented for the first time. Highernorder approximations are also discussed. We show the accuracy of thenperturbation formula, reveal that the torsional and radial-axial modesnare not pure in cubic fibers, and inspect the modal birefringencenphenomenon