Study On Lapping And Polishing Process Of Gadolinium Gallium Garnet

Gadolinium gallium garnet(GGG)is a kind of laser crystal with excellent properties which is widely applied in solid-state laser.Nowadays,after the high power laser diode pump technology and its supporting technology have obtained an important breakthrough,solid-state laser is developing rapidly from small and medium-sized power to high-power.GGG crystal is the best choice for the high-power solid-state laser.A laser crystal in solid-state laser requires GGG crystal with suitable flatness and roughness in order to achieve a higher laser threshold value.However,the research of the manufacture process of GGG is limited to a particular process' optimization,rather than an entire one.Therefore,we studied and optimized the parameters of the lapping and the polishing process.The main contents are as follows:(1)Mechanical lapping process was studied.The mechanical lapping process includes rough lapping and precision lapping.Suitable parameters of rough lapping process were chosen in order to avoid the fragmentation and make the GGG wafer become thinner quickly.The parameters of precision lapping process were optimized through the single factor experiments,which improved both the flatness and the roughness of GGG wafer.(2)Mechanical polishing technology was studied.The phenomenon that the appearance of surface defects when GGG wafer was polished with harder polishing pad and smaller particle size(W1-W2.5)abrasive was analyzed and researched from the aspects of the hardness and size of the abrasive and the hardness of polishing pad.We thought that the root reason of this problem is that the polishing pad's hardness.Through the trajectory calculation and simulation,the motion form of mechanical polishing on polyurethane polishing pad using eccentric holding ring was determined.The parameters of mechanical polishing process were optimized through the single factor experiments and the rotational speed and load.The GGG wafer's flatness of 140 nm and roughness RMS of 21.9nm are achieved.(3)Mechanical chemical polishing process was studied.The pH and the ludox concentration of the polishing solution were optimized.IC1000 polishing pad was chosen in order to avoid the deterioration of flatness during the polishing process.The measurement and fitting of the paste base and the flatness of polished wafers are determined and a diamond pad conditioner was applied to fit the polishing pad with the suitable parameters,which improved the roughness of GGG wafer and reduced the flatness deterioration at the same time.(4)The entire manufacture process was obtained and GGG wafer can be manufactured effectively with the combined process above and a flatness of 276 nm and a roughness of RMS 0.45 nm could be achieved.The surface of GGG wafer was analyzed with no defects.