Abstract
In this paper, on the basis of electromagnetic fields in statistical formulation and the material description for solid medium, the governing equations are decomposed into different states with the necessary approximations. The relevant equations with boundary equations are applied to investigate the phase change of electromagnetic wave and the mode transition of guided electromagnetic wave in a slab waveguide, which is caused by the mechanical disturbance such as strain or elastic wave. The conditions of the mode transition for TE mode are determined and the physical meaning of the results is interpreted.