Comparative Study Of Zro <sub> 2 </ Sub> Chemical Film And Physical Membrane Damage Mechanism

With the developing of laser technology, new type of laser(such as ultra-high power, ultra-fast lasers, et. al) was developed. This turns new requirement for the optical films. Optical thin films are the most important and weak components of high-power laser system. The laser damage of optical thin films made its application in high-energy and high-power laser limited. , which becomes one of the "bottleneck". In recent years, more and more attention has been paid to ZrO2 chemical film fabricated by sol-gel process because of the excellent optical properties and resistance to laser damage. Therefore, the continuous improvement of its performance, the increase of film resistance to laser intensity, and the development of new thin film technology, has great important scientific significance and engineering applications.Five batchs of physical and chemical zirconia monolayer films with different thickness were deposited on K9 glass substrates using electron beam evaporation and sol-gel process, respectively. The laser-induced damage threshold (LIDT) of the two kinds of films was measured. Thermal absorption, refractive index, porous ratio and surface morphologies, impurity and defect of films were investigated by transmissive optical thermal lens , ellipsometer, atomic force microscopy and phase contrast microscopy, respectively. The results are as following.(1) The LIDT of chemical ZrO2 film is significantly higher than that of the corresponding physical film. As the thickness of ZrO2 film increased, the LIDT is decresed for both kinds of films.(2) Compared with chemical film, the physical film have larger thermal absorption. The thermal absorption increases with the film thickness increasing.(3) The refractive index of chemical film is smaller than that of physical film. Using the relationship between refractive index and porous ratio, the porous ratio was calculated. The porous ratio of two types of films are slightly decreased with film thickness increaseing. The porous ratio of the physical film is much smaller than that of chemical film. (4) The relationship between damage threshold and microstructure characteristics had been analyzed. LIDT of physical film is lower than that of chemical film because that physical film has more impurities and defects, which induce higher thermal absorption. The fabrication process of chemical film was simple and easy to control. The structure of chemical film is more uniform and porous than that of physical film. This made it absorb less laser energy, scattere and lose absorbed energy through the porous structure more easily.