Preparation Of Sol-gel Nb₂O₅ Preparation Of Sol-gel Nb₂O₅ Thin Films With High Laser Damage Resistance And Exploration Of Laser Damage Mechanism

In the laser system,Optical films always play an important role in laser systems.Once the film is damaged,it will affect the function of the entire system.Therefore,with the development of laser technology toward higher power density,it make a corresponding higher demand for the laser-induced damage threshold?LIDT?of optical films.Nb₂O₅ material has high refractive index and good chemical resistance and is widely used in the field of optical films.The Nb₂O₅ film was prepared by sol-gel method and the optical properties,laser damage threshold and temperature effect of Nb₂O₅ film were systematically studied in this paper.The variation of threshold and damage morphology was studied to learn the damage mechanism of Nb₂O₅ film.Finally,a method for improving the LIDT of sol-gel Nb₂O₅ film was sought by adding a SiO₂ film addition layer.Firstly,Nb₂O₅ films were prepared by adding different additives.The viscosity of the Nb₂O₅ colloids and the optical properties,phase structure,root mean square?RMS?,weak absorption and damage thresholds of Nb₂O₅ film were discussed in detail with effects of acetylacetone?ACAC?,diethanolamine?DEA?and citric acid?CA?.The experimental results showed that the colloid prepared by ACAC was the most stable.The surface of the film prepared by DEA was the most flat.The film prepared by CA had the highest optical transmittance and the lowest weak absorption value,and the highest laser damage threshold obtained is 24.9 J/cm².According to the LIDT and damage morphology,the structural evolution model of the film was proposed to describe the specific bonding mode of different additives to Nb₂O₅particles.Secondly,the Nb₂O₅ films prepared by the three additives were annealed at150°C and 250°C respectively.It was found that the Nb₂O₅ films prepared with CA had the highest LIDT after annealing,which were 23.5 J/cm² and 17.7 J/cm²respectively.However,the films were treated in the in-situ environment at the same temperature,and the threshold contrast annealing treatment was further reduced.The Nb₂O₅ film prepared by DEA had the highest laser damage threshold at the in-situ high temperature of 250°C,reaching 18.9 J/cm².Then the effects of different in-situ temperatures on the optical properties and laser damage threshold of Nb₂O₅ films were studied.The Nb₂O₅ film prepared by CA was used.The results showed that when the initial temperature was increased from room temperature to 100°C,the LIDT of the film was 21.8 J/cm².When the temperature was increased to 150°C,the LIDT of the film was 20.4 J/cm².When the temperature was increased to 200°C,the LIDT of the film was 19 J/cm²,which was lower than the LIDT of normal temperature,but the film still maintained the high LIDT at two in-situ temperatures.Finally,the LIDT of the Nb₂O₅ film was improved by adding a SiO₂ addition layer.A sample was prepared by using a SiO₂ film as a buffer layer,an intermediate layer,and a protective film,respectively.The results showed that when SiO₂ film was used as a protective film,its optical transmittance was the highest,but its LIDT was the smallest,being 27.2 J/cm².When the SiO₂ film was used as a buffer layer,its LIDT was the highest,being 31.2 J/cm².Among them,the SiO₂ film had a very high LIDT of 34.7 J/cm² by itself.