Electron avalanche breakdown induced by ruby laser light

Ruby-laser-induced intrinsic bulk damage in nine alkali-halide crystals is reported. Within experimental error and for all of these crystals the damage field is greater than or equal to that measured at 1.06 μm and dc. The trend in breakdown fields among these crystals at 0.69 μm differs from that at longer wavelengths and suggests that, even though electron avalanche breakdown is the likely damage mechanism, the first signs of a frequency dependence to this process appear by 4.3×1014 Hz.