Theory of in-plane motion induced by laser action on crystal surface

Abstract
Interaction of ultrashort laser pulses with subsurface region of the material leads to the excitation of acoustic waves initially propagating both in the direction from the surface and in the direction to the surface. Even if the acoustic waves inially propagating in the direction from the surface do not return to the surface in form of an echo (because of their absorption) there is still an opportunity to get information on the optoacoustic transformation by detecting the motion of the crystal surface caused by the waves initially propagating towards the surface. This monitoring of the surface motion should be accomplished immediately following the laser action.