THE TRANSMISSION CHARACTERISTICS OF THE ELASTIC SHEAR WAVE AT A SEMI-INFINITE EFFECTIVE CHIRAL MEDIUM

The plane wave propagating in effective chiral (isotropic, non-centrosymmetric) materials had been asymptotically investigated. They can be constructed by embedding structural chiral microstructures in a host medium, and six independent wavenumbers can hence be observed from the dispersion equations. Two of the wavenumbers represent the non-dispersive longitudinal waves while the remaining four represent the dispersive circularly polarized shear waves. The dispersion equations also indicate that two transition frequencies divide the frequency spectrum of the transverse wavenumbers into three different groups and the four transverse mode can only be distinguished in a specified frequency range. To continue our previous research, the field equations governing the harmonic motions at the achiral–chiral interface are written as a matrix form to solve the reflected and transmitted wave fields. Numerical results show that the P-, SV-, and SH-waves are coupled together when an elastic shear wave is incident at the achiral–chiral interface. Meanwhile, the two coupled transverse waves, i.e., the LCP and RCP plane waves, will degenerate to a linearly transverse plane wave when the shear wave is incident normally. The phenomenon may explain why the mode conversion due to the chirality is particularly enhanced between the first and second transition frequencies.