Laser damage of CaF2(111) surfaces at 248 nm

Single-shot laser damage of polished and cleaved CaF2(111) surfaces induced by (248 nm)(14 ns) pulses was studied by electron microscopy and probe beam deflection. It is shown that the onset of laser damage is fracturing rather than melting. The fragment thickness is found to increase with fluence which points to an enhanced near surface absorption of about 0.4 μm characteristic depth. Bending of the fragments with typical curvature radii around 100 μm indicates that within this fragment thickness a transition to plasticity has taken place.