LASER DAMAGE OF CAF2(111) SURFACES AT 248NM

Single-shot laser damage of polished and cleaved CaF2(111) surfaces in duced by (248 nm)/(14 ns) pulses was studied by electron microscopy an d probe beam deflection, It is shown that the onset of laser damage is fracturing rather than melting. The fragment thickness is found to in crease with fluence which points to an enhanced near surface absorptio n of about 0.4 mu m characteristic depth. Bending of the fragments wit h typical curvature radii around 100 mu m indicates that within this f ragment thickness a transition to plasticity has taken place.