Study On The Influence Of 1064nm/532nm Lasers On The Damage Threshold Of Thin Films

The anti-laser damage ability of optical films is an important indicator to measure the safeuse range of optical components in high-energy laser systems.High-reflection and anti-reflection film elements are important components in high-energy laser systems.In order to achieve ideal laser transmission effects,it is necessary to continuously optimize the film system design and preparation process to meet the performance requirements of the transmission window.The damage of thin films will be caused by strong laser on the surface of thin films,and the mechanism of damage induced by laser at different wavelengths is different.In the field of strong laser applications,most of the research on damage focuses on the regular film system,while the research on the irregular film system is not enough.Based on this,this thesis analyzes the influence of different wavelengths on the damage of films from a number of theoretical perspectives closely related to wavelengths.Taking monolayer films and irregular films as the research objects,a variety of monolayer films and irregular films were designed and fabricated,and the effects of 1064nm and 532nm wavelengths on resistance to laser damage properties were studied.The main research conclusions are as follows:The relationship between wavelength and film damage is studied from the theoretical aspects of damage probability,material absorption,stimulated radiation and defect absorption,energy band theory,and multi-beam interference,which are closely related to laser wavelength.The results show that with the increase of the laser wavelength,the damage probability of the thin film decreases,the damage threshold increases,and the anti-laser damage ability is enhanced.Using electron beam thermal evaporation technology,monolayer film with different thickness,multilayer irregular anti-reflection film and high-reflection film are respectively plated on K9 glass substrate.SiO2,TiO2,HfO2,Ta2O5 monolayer films are prepared and their thicknesses are measured.The results show that the thickness of the designed monolayer film meets the requirements.The dual-band irregular anti-reflection film and high-reflection film are designed and fabricated,the initial film system of the anti-reflection film is G|HLHL|A,and the initial film system of the high-reflection film is G|(HL)XH|A.The high refractive index materials are TiO2,HfO2,Ta2O5,and the low refractive index material is SiO2.According to experimental tests,the average transmittance of the anti-reflection film at 520nm-540nm and 1050nm-1080nm is greater than 95%,and the average reflectivity of the high-reflection film is greater than 97%.Using a dual-wavelength common optical path test system,the effects of different parameters on the laser damage threshold of the monolayer film are tested in the 1-on-1 laser mode.The study finds that as the wavelength tends to be longer,the ability of the monolayer film has been improved in different degrees.With the increase of the film thickness,the anti-laser damage ability of the monolayer film at the same wavelength is reduced.The analysis of the damage morphology of the monolayer film shows that the laser-induced damage is random and the damage morphology is different,which is related to the thermal effect of the single-pulse laser.The influence of different experimental parameters on the laser damage threshold of the multilayer irregular film is explored.It's found that with the decrease of the laser wavelength,the anti-laser irradiation ability of the irregular film decreased.At the same wavelength,the damage threshold of the highly reflective film generally higher than the anti-reflection film.When the wavelengths are different,the smaller the value of the standing wave electric field strength of the same film at the air-film interface,the higher the laser protection ability.Analysis of the damage morphology of the multilayer films shows that there is a single circular damage spot outside the laser damaged area of the HfO2/SiO2 high-reflection film,and the rest of the irregular films only have damage pits left by the direct action of the laser.In this paper,we test and analyze the damage thresholds of monolayer films and irregular films under different laser wavelengths,and discuss the damage process and damage mechanism of optical films.The research results have guiding significance and important practical value for improving the thin film deposition process,clarifying the direction of increasing the laser damage threshold of thin film,extending the service life of optical thin film,and strengthening and safety of laser systems.