Mechanism of laser induced ripple damage on a film mirror

Pulsed laser induced ripple damage on an aluminum film mirror has been investigated from experiments. Ripples have been found at the periphery of damage site using atomforce microscope(AFM)，in most cases, several set of ripples appear at the same time in the same area. A laser interference theoretical model has been presented to explain pulsed laser induced ripples at the periphery of damage site in optical surface. This model assumes that the impurity grain or laser induced sphere-like distortion at the surface of optical sample reflects or scatters laser beam to its periphery area, and this reflected or scattered beam interferes with laser beam irradiated directly on this area. So the beam spatial profile becomes periodic and ripple damage morphology forms instantly. A simulated exper