Interaction of laser pulse with confined plasma during exit surface nanosecond laser damage

Abstract

Interpretation of spatial and time resolved images of rear surface ns laser damage in dielectrics requires understanding of the dynamic interaction of the incoming laser beam with the confined expanding plasma in the material. The detailed kinetics of the plasma, involving both expansion and retraction, depends on details of reflection and absorption in the hot material. The growth of the hot region is treated using a model previously developed to understand laser peening. The pressure is found to scale as the square root of laser intensity and drops off slowly after energy deposition is complete. For the conditions of our experimental observations in fused silica, our model predicts a pressure of about 9 GPa and a surface expansion velocity of about 1.5 km/sec, in good agreement with experimental observation.

Difference in laser-induced damage behavior between back and front surfaces

“…Furthermore, plasma influences the effect of multi-pulse laser processing or drilling. The suppression effect of the plasma on the front surface damage and the enhancement effect on the back surface damage lead to different processing effects [15][16][17][18][19].…”

The Influence of High-Frequency Phase of Laser Wavefront on the Distribution of Focal Spot

“…When laser beam is effected on the material, the surface properties of material can be damaged, which is disadvantageous for optical elements or some precise instruments [1,2] . The damage effect is decided by the power, shape and size of laser beam [3][4][5] . Moreover, some researchers thought that the damage effect is influenced by the wavefront phase (especial high-frequency phase) of laser beam too [6] , because that the distribution of wavefront phase can affect the distribution of far field intensity, especially, the high-frequency phase of wavefront can result in side lobe into the focal spot.…”