Study On Surface Quality Of Optical Components Base On Optical Loss

The development of modern laser technology puts forward higher requirements on the surface quality of optical components. Especially in high power laser system, the surface quality of optical components is an important factor to restrict its further development. The effective measurement about the surface quality of optical components is of great importance to optimize the polishing process of optical components, optimize the coating process and reduce the loss of coating components. Therefore, in this thesis, the surface quality of optical components is investigated base on scattering and absorption loss.Firstly, light scattering is used to investigate the surface quality of optical components. The total scattering(TS) value of optical components which have different level of the surface quality is measured, and the result is that the better the surface quality of optical components is, the smaller the TS value is. If optical components have the same level of the surface quality, their TS values are very close. If TS value of optical component is smaller than 30 ppm, its surface is regarded as super-smooth surface. The scanning scattering maps of optical components which have different level of the surface quality are studied, and the result is that the better the surface quality of optical components is, the fewer the defects in the scattering maps are and the smaller the whole TS value is. Besides, TS value and scattering map are used to distinguish the level of surface quality of two large aperture optical components, the same conclusion is reached.Secondly, the connection between defects on scattering maps and actual defects on optical components is investigated, it is found that defects on scattering maps must cover the actual defects on optical components, but both are not equivalent. Because of the large measuring spots, the size of both defects is not equal. The connection between total scattering and surface roughness and surface defects is also investigated, and it is found that total scattering is the result of surface roughness and surface defects. Mie scattering theory is used to calculate the TS value of a surface defect of 1um in diameter, and the experimental result is verified.Finally, absorption loss is used to investigate the surface quality of optical components. The difference of absorption of optical components is studied by laser calorimetric technique, and the result shows that the value of absorption of optical components with high reflection film is obviously smaller. The absorption at the defect position is studied, and the result shows that the value of absorption is obviously larger. Surface thermal lens technique is used to measure the absorption of optical components by scanning. The connection between defects on absorption maps and actual defects on optical components is investigated, and the result shows that the position of both defects is a good agreement. Because of the large measuring spots, the size of both defects is not equal. Besides, the scanning absorption maps of optical components with different surface quality is studied, and the result shows that the better the surface quality of optical components is, the fewer defects on absorption maps is, and the smaller the whole absorption value is.