Effect of optical penetration on laser generated thermoelastic ultrasound in solids

The effect of optical penetration on laser thermoelastically-generated ultrasound in nonmetallic solids is studied theoretically on the basis of thermoelastic equations.In one-dimensional model,the general expression of wave displacement is obtained by solving the thermal diffusion and thermoelasticdisplacement equations,from which the influence of optical absorption on the displacement amplitude isanalyzed.In the case of two-dimensional axial symmetry,on neglecting the thermal diffusion,we solve thethermoelastic wave equation by means of the integral transform method and obtain analytic expressionsof the wave displacement components in the far-field.Directivity patterns of both longitudinal and shearwaves are presented and discussed.