In order to study the scaling laws of optical components, we set up a model based on the heat conduction theory and thermodynamic theory. Then the similarity theory was used to the model analyzation. Finally, we demonstrate three conclusions which are related to the practical engineering application. The first one is that thermal damage behaviors of different scale optical components are similar when the linear power density of irradiated laser are the same. In other words, we should use the linear power density to represent the resistance of damage tolerance for optical components The second one is the judgement standard of scram time. We find the scram time of large-aperture system is certain times as much as the scram time of small-aperture system. The third one is about how to design the scaled experiment can we make two different scale laser systems obey the similar thermal damage behaviors. This study is of great help for the damage prevention of the optical components.
The thermal stress damage of optical elements always restrict the development of high power laser system. We studied the thermal damage mechanism of the optical elements with contaminants induced by high power continuous wave (CW) lasers. An experiment was carried out by a self-build optical element testing platform and a model based on the temperature field theory and thermodynamic theory was set up. We recorded the thermal stress damage process based on a 10 kW/cm<sup>2</sup> level mid-infrared continuous wave laser. Then we calculated the thermal damage process of optical elements. The calculated results are in agreement with our experimental record. The results showed the success of modeling calculation in the thermal damage mechanism caused by contaminants.
To study the thermal damage process of optical film induced by continuous wave lasers, a model with contaminants on the surface of optical film is established. Based on the temperature field theory and heat conduction theory, we apply finite element method (FEM) to calculate the thermal damage process of the optical films. The results show that contaminants on the surface play an important role in the damage process of optical film. Finally, we compare the calculated results with our experimental data, and the calculated thermal damage process of film is in agreement with our experimental record.
In order to study the damage characteristic of the contaminated resonating mirror in high power continuous wave (cw) laser system, we established a theoretical model based on the optical transmission theory with a gain medium. The optical propagation in the cavity is calculated utilizing a Fast Fourier Transform (FFT) repeatedly until the convergence of the calculations tend to a steady-state oscillation mode pattern. The influence of the contaminant size, the contaminant number and the cavity structure on the damage characteristic of the resonating mirror is studied in the theoretical model.