On the Propagation of Waves in an Anisotropic Solid with Laser-Induced Atomic Defects

Abstract

The behavior of plane waves in a linear, elastic anisotropic laser-excited solid has been investigated taking into account the effects of atomic defect generation. It is found that there are four types of dispersive waves in these crystals, namely, a quasilongitudinal (QL-mode), two quasitransverse (QT-mode), and a quasidefect concentration (N-mode) wave. The complex secular equations for cubic and transversely isotropic crystals are reduced as special cases. It is demonstrated that when waves propagate in one of the planes of transversely isotropic solid having defect concentration field, only one purely quasitransverse wave decouples from the rest of the motion and is not influenced by defect concentration changes. The other waves are coupled and get modified due to presence of defects. When waves propagate along the axis of the solid, only QT- and N-mode are coupled, whereas the two QT-modes get decoupled from the rest of the motion. The phase velocities and attenuation factors of waves have been obtained. Significant effect of defects and anisotropy on wave characteristics is observed in certain ranges of frequency. It is also shown that there is an appreciable variation in case of QL-mode as compared with QT- and N-mode.