The effect of changes in laser-induced stress upon irradiation of monocrystalline silicon was studied in detail using Mach-Zehnder interferometer, high speed camera and computer processing system, real-time detection of stress distribution and stress evolvement under different laser fluences and pulse widths. After irradiation, the changes of interference fringes were used to calculate the stress value. The results show that the stresses increased with the increase of the laser fluence. The formation of stress could be explained using thermoelastic theory. The cleavage plane's dislocation appears in the following sequence: (1 1 1) plane appears and then the dislocation slip of (1 1 0) cleavage plane appears. In addition, it is found that cleavage plane of (1 1 1) mainly exist in the spot and cleavage plane of (1 1 0) mainly exists in the vicinity of spot radius. Stress areas mainly exist in the thin layer on the surface of silicon. Furthermore, stress field was analysed by the finite-element method to get a better understanding of the formation and distribution of stress. Under the same experimental conditions, the numerical results are in agreement with the experimental values.

The thermal stress effects of the fused silica irradiated by a millisecond–nanosecond (ms–ns) combined pulse laser are analysed. Numerical results are in good agreement with the experimental results. The results show that (1) different pulse delay and energy density affect the temperature change of the fused silica; (2) observing the axial stress, it is found that nanosecond laser will lead to new damage areas near the film under the condition of millisecond laser pre-irradiation and (3) stress exfoliation is found in the study of damage morphology.