Laser Cleaning Of Optical Components Research

Laser cleaning is a technique that use laser irradiation to vaporize or eject contaminants,rusts and coatings on solid surface, thereby reach a clean level. Laser cleaning satisfies the need of removal submicron particles in the industry. Compare with traditional clean technique, laser cleaning has obvious advantage in environment protection and high precision. Cleanness is a widely used parameter to judge the clean effect; it is the ratio of pollutants removed by the total pollutants. Besides, microscope and balance can help to estimate the clean effect.In this dissertation, theoretical analysis and experimental test are used to investigate irradiations of CO2 CW laser and pulsed Nd:YAG 3ωlaser on optic glass surfaces that has different contaminants. Optical microscope, UV-VIS spectrophotometer, FT-IR and interface intention measurement are used to get the measuring data. Conclusions are as follows:1. According to micrograph and transmission spectrum, it's found that the pollution level caused by skin grease is highest, fingerprint is the medium and silicon is low. Raman-shift spectrum and surface tension measurement results show that samples contaminated by fingerprint and skin grease had some similarity.2. By CO2 laser irradiation, radius of the three type pollutants are decreased as CO2 laser irradiation increased. But the pollutants are not removed totally. The samples would have a split when the power of laser is high enough, which shows a contradictory between cleaning effect and load capacity of glass. Transmission spectrum can be greatly improved for the sample polluted by skin grease if laser power increased. Surface tension data show that after laser irradiation, the skin grease sample is close to clean K9 glass.3. By Nd:YAG 3ωlaser irradiation, transmission of samples with clean films that is decreased in some waveband, while soakage is decreased as the pulse overlap increased. For the samples with polluted films irradiated by the same energy, area of pollutants is decreased as the pulse number increased. For the samples with polluted films irradiated by the same pulse number, area of pollutants is decreased as the pulse energy increased. Low energy but repeating pulse, and high energy but single pulse may cause same result. Degree of the darkness is increased as the pulse overlap increased.4. Ostu algorithm is used to convert origin microscope photos to binary images. Cleaning efficiency of CO2 and Nd:YAG 3ωlaser is compared. Results shows that CO2 laser is suitable for clean the optic surface which has heavy pollutants, while Nd:YAG 3ωlaser is suitable for clean the optic surface which has light pollutants.