An experimental demonstration of the effect of mechanical stresses on the laser generation of acoustic vibrations in various materials

The process of generating an acoustic signal during laser heating of metals and dielectrics is analyzed in the framework of the theory of thermoelasticity. A comparison of the experimental optoacoustic signal and the theoretical distribution of mechanical stresses for plates with a hole of aluminum alloy and silicon nitride is performed. It was found that the standard theory of thermoelasticity can qualitatively describe the dependence of the optoacoustic signal on the stress near the hole in the silicon nitride plate, but is not enough to correctly describe the dependence of the signal on the stress near the hole in the metal plate. It is noted that in order to achieve agreement between the obtained experimental and theoretical results for metals, in addition to the thermal effect of laser radiation on the lattice, it is necessary to take into account the additional effect of the electron system.