Study On Laser-induced Damage Threshold And Temperature Effect Of Ta₂O₅ Films Prepared By Sol-gel Method

Optical films are important components of laser system.With the development of laser technology toward higher power density make a corresponding higher demand for the laser-induced damage threshold(LIDT)of optical films.So to study the laser damage mechanism of the optical films is of important significances to improving the power of the lasers.Ta2O5 is widely used in the field of optical films due to its high refractive index,good chemical stability and low absorption.Meanwhile,since Ta2O5 films has high laser damage resistance,it has attracted much attention in the application of laser films in recent years.In this paper,Ta2O5 films are prepared by sol-gel method with high LIDT,the optical properties,LIDT and the temperature effect of Ta2O5 films were systematically researched.And through the investigation on the change rule of its LIDT and damage morphologies.We also try to explain the damage mechanism of Ta2O5 films in this paper.First,the research background,research progress on laser damage,the structure and optical properties,and the preparation methods of Ta2O5 films are introduced.At the same time,we mainly introduced the sol-gel method for preparing Ta2O5 films in this paper,including its basic principle,film forming method and its advantages and disadvantages.At last,the mechanisms of the measurements applied in the whole process of investigation of Ta2O5 films are also introduced,and the significance and content of this paper is given.We studied the influence of key parameters on the properties of Ta2O5 sols and films during the preparation of high LIDT Ta2O5 films by sol-gel method.The highest LIDT of the Ta2O5 films obtained in this study is 24.1 J/cm2.Moreover,based on the experimental results,a pseudo-ternary phase diagram of H2O2-HNO3-Ac Ac system for preparing high LIDT Ta2O5 films is proposed,which is helpful to have a better understanding of the preparation process and obtain Ta2O5 films with higher laser damage resistance in the future.Ta2O5 films were prepared by the sol-gel method using TaCl5 as precursor with two additives.The two additives affected the optical properties,surface roughness,absorption and LIDT of Ta2O5 films were researched.The results showed that the two additives can greatly improve the stability of sols and the LIDT of films,and the highest LIDT of the Ta2O5-DP films is 30.3 J/cm2.At last,we also discussed the damage mechanism of Ta2O5 films with two additives.The LIDT at different initial temperatures of Ta2O5 films was investigated by an in situ high temperature laser-induced damage testing platform.It was shown that,when theinitial temperature increased from 20 ? to 100 ?,the LIDT at 1064 nm and 12 ns significantly decreased by nearly 10%.Different damage morphologies were found at different initial temperatures.Moreover,based on the defect-induced damage model,the temperature evolution of the defects were theoretically calculated to explain the damage characteristics and mechanisms at different initial temperatures.It is found that with the initial temperature being increased,the thermal-stress coupling damage mechanism transformed gradually to the thermal dominant damage mechanism.