Study On Fixed-abrasive Lapping And Chemically Mechanical Polishing Of Yttrium Aluminum Garnet Crystal

With the development of laser technology,high power solid-state lasers are increasingly used in industrial,military,medical and scientific research fields.Among the high power solid-state lasers,disk solid-state lasers have the advantages of lightweight,small size,high efficiency,stability,good beam quality and low maintenance costs and become the mainstream in applied lasers.Yttrium aluminum garnet(YAG)is the most widely used matrix material for solid-state lasers.Aiming at the problems of current YAG crystals free abrasive grinding and polishing in which the processing efficiency is low,the surface damage is serious,and the polishing time is long,the combined process of ‘fixed-abrasive lapping and chemically mechanical polishing’ is proposed to achieve high-efficiency and low-damage processing of YAG crystals.Through the single-factor test analysis,ethylene glycol aqueous solution is selected as the lapping fluid.3M 673LAA10 pad is used as the fixed abrasive pad to coarsely lap the YAG crystals.The orthogonal experiment is used to optimize the process parameters to obtain a rough surface of the YAG disk with a surface roughness of Ra= 151.65 nm.The thickness of the rough lapping damage layer is approximately 6 μm as measured by differential etching and cross-section magnification.The rough lapping YAG is fine lapped by using #6000 sandpaper manufactured by 3M corporation to obtain a YAG disk with a surface roughness Ra= 0.55 nm and a damage layer thickness of about 1.5 μm.A chemically mechanical polishing process suitable for YAG crystals is proposed.The chemically mechanical polishing slurry is prepared by microscopic observation of the polishing effect,XPS detection chemical composition and Zeta potential measurement.Through the single factor analysis and the orthogonal test to optimize the process parameters of the process,a low-damage YAG disk with a surface roughness Ra= 0.74 nm and no significant damage after etching is obtained.By studying the surface quality and damage layer changes,it is verified that the combined process proposed in this thesis requires only about 2 hours of processing time and can save 3-6 hours of processing time compared with the traditional processing methods.And a more smooth and low damage machining surface can be obtained.The high efficiency and low damage processing of YAG crystals is realized.