Numerical simulation on the damage behaviors of optical mirrors induced by film defects in high-power CW laser

Abstract

In order to study the damage behaviors of optical mirrors induced by film defects (as film bumps, film pits and film contaminants) in high-power CW laser, a simulation study was carried out, which considered temperature, thermal stress and thermal deformation in results. The results show that the bumps of the film will primarily absorb laser energy, and its temperature, thermal stress and thermal deformation will become extremely high, which is easy to damage the film; similarly, the film pits will also absorb laser energy for its temperature rise, and the pits will expand to the inwards. The larger the size of the pits, the larger the expansion of melting range will be, and eventually damage the film layer; after absorbing the laser energy, the temperature of the film contaminants is very high (for film contaminants size of 150 μm, its maximum temperature reaching 900 K), even exceeding the damage temperature (523 K) that the film can withstand, and finally causing the film to be ablated.