Theoretical study of laser induced thermal damage on the narrowband filter optical thin film

Abstract

In the experimental study of the film's thermal damage, an extremely high power density is needed. In order to achieve such high power density, the incident beam is generally converted. In this situation, the cone's angle of the converted beam is inevitable. A narrowband filter optical film is taken as an example. The influence of the beam cone angle on the thermal damage of the optical film is theoretically studied. Under the irradiation of high energy laser, the film absorbs the laser energy and the heat is accumulated continuously in the film. The cone's angle influences the laser intensity distribution, i.e. the heat source, in the multilayer film. The temperature distribution and the temperature rising process are also related to the cone's angle. Only if the cone's half angle is smaller than 3°, the influence of the cone's angle can be ignored.