Analysis Of Laser Thermal Effects Damage On Optical Materials And Films

Ever since the invention of the laser, laser has been drive towards high power, wide coverage-range of wavelength, short pulse duration, solidification and miniaturization. At present, lasers have been applied to most fields of national economy, national defends and people's daily life. Since there are many optical components, which involve a great deal of optical medium and thin films, the interaction between laser and optical dielectric & optical thin film has attracted intensive attention. High-energy system involves an optical train consisting of reflections and windows, in which temperature, stress and deformation may happen because of the absorption of laser beam energy, so that the beam quality and transmission of energy to far field will be affected, Also it may induced the damage of optical components.Most methods to research thermal effect are based on the analytical method, but the calculation processing is too complex, and we can get analytical solution only in a very small number of simple cases. We research the issue by use of finite element method (FEM). In this paper, the main research areas are as follows: The first, the typical experiments of damage, as well as the mechanism of damage are discussed. The second, in this paper, a theoretical mode of pulse laser leading to thermal stress damage of dielectric material and film is developed. Based on this theoretical model, transient distributions of temperature field and thermal stress field are analyzed by finite element method (FEM). The FEM method involves element discretion, element analysis, and overall analysis. The third, transient temperature field and stress field are simulated by using FEM software ANSYS. Numerical results indicate: There is large temperature gradient in radial directions, while small temperature gradient exists in axis directions. And central temperature will be higher as power density of laser is higher. The results Also demonstrate that thermal stress damage is critical and circumferential stress play a main role in damage mechanism. The forth, the principle and methods of film measurement are summarized, the results in this paper may provide theoretical base for further research.