Insight into an Efficient Slurry for Chemical Mechanical Polishing of YAG Based on a Pitch Pad

Yttrium aluminum garnet (YAG) is a key material for fabricating laser devices. Its surface quality and shape accuracy are critical to optical performance and operational reliability. The pitch lap enables high surface shape accuracy in the ultraprecision polishing of YAG crystals. However, a slurry compatible with the pitch lap remains insufficiently investigated, which limits further improvement in surface quality while preserving surface shape accuracy. In this paper, a slurry specifically designed for use with the pitch lap was developed. The effects of abrasive type, particle size, concentration, acid type, and slurry pH on the surface quality of YAG crystals were systematically investigated. Surface roughness (Sa) and material removal rate (MRR) were used as the primary metrics for optimizing the slurry components. The optimized slurry yielded an ultralow Sa of 0.25 nm and a high MRR of ∼170 nm·min^-1, enabling both ultrasmooth surfaces and efficient material removal. Furthermore, X-ray photoelectron spectroscopy was used to characterize the evolution of surface chemical states before and after polishing, providing insights into the material removal mechanism. The results indicate that material removal is promoted by the synergistic action of chemical and mechanical effects. These findings provide an alternative technical route and a theoretical basis for high-efficiency, high-quality polishing of YAG crystals.