Short and intense Iaser pulse can process the surface and the inside oftransparent materials by focusing the pulse at desired position. Processing ofsuch a transparent material is considered to be app]icable to a lot of practica] applications. Details of such process are, however, still unclear and are subjects of fhrther investigations. Here we report on dynamical observation about interaction of fundarnental radiation (1064nm) of the Q-switched Nd:YAG laser to the surface of PMMA obseryed by

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... n imaging system with nanosecond time resolution, The system uses fundamental radiation ofa Q-switched Nd:YAG laser as a processing laser and second harrnonic radiation (532nm) of another Nd:YAG laser as illuminating light. We observed stress wayes which propagate into the material and into the atmosphere by shadowgraph, schlieren and photoelastic method. We distinguished three different types of waves propagating into the bulk samples. The contrast of photoelastic images depends on raser pulse energy, Based on this result, we try to examine the effects of incidence angle of the laser to coupling between ]aser radiations and the material and found that magnitude ofstress wave correlates with laser fluence.