YAG Crystal
1. Introduction
YAG (Yttrium Aluminum Garnet, Y₃Al₅O₁₂) crystal is an excellent laser and optical material known for its high hardness, high thermal conductivity, good chemical stability, and superior optical homogeneity. It is widely used in solid-state lasers, LED phosphor substrates, optical windows, medical laser equipment, and defense electro-optical systems.
Hemei Company possesses profound technical expertise in the precision machining of hard and brittle materials. It has developed an efficient and stable polishing process specifically for YAG crystals, enabling fully controllable processing from rough to fine polishing. This ensures the YAG crystal surface meets the quality standards for "laser-grade" or "optical-grade" applications.
2. Application Requirements
The polishing objectives for YAG crystals include:
Surface Roughness (Ra) reduced to < 0.5 nm.
Surface Figure Accuracy (PV Value) better than λ/10 (@632.8 nm).
Surface free of damage and sub-surface cracks, meeting the laser-induced damage threshold (LIDT) requirements.
Thickness Uniformity (TTV) controlled within a specified micrometer range.
To achieve these objectives, the Hemei process utilizes a customized bonding system and a multi-step polishing procedure, ensuring geometric accuracy and surface integrity during processing.
3. System Specifications
Hemei's modular polishing system supports the processing of YAG crystals in various sizes and shapes. The core system includes:
HSM-L/LP Series Lapping Equipment: Used for initial material removal and thickness control.
HSM-CMP Series Chemical Mechanical Polishing (CMP) System: Used to achieve an ultra-smooth, damage-free surface.
Key Subsystems:
Wafer/Crystal-specific Bonding Unit (WBU)
SJ/ASJ Series Precision Polishing Fixtures
C-ASJ Drive Head High-Speed Polishing System
4. Processing Flow
Bonding and Mounting: The YAG crystal is temporarily bonded to a support plate using the WBU and then mounted onto the polishing fixture.
Rough and Intermediate Polishing: Controlled lapping is performed on the HSM-L equipment to remove the damaged layer from machining.
Fine Polishing: The HSM-CMP system is used for the final polish. By adjusting parameters such as pressure, rotational speed, and slurry flow in real-time, a nanoscale surface finish is achieved.
5. Typical Results
Surface Roughness: Ra < 0.5 nm
Surface Figure Accuracy: PV ≤ λ/10
Material Removal Rate: 1-2.5 μm/hour (adjustable)
Applicable to YAG wafers up to ≤ 6 inches in diameter and irregularly shaped crystals.
6. Summary
Hemei Company provides a complete and reliable polishing solution for YAG crystals, capable of consistently achieving nanoscale surface quality and high optical performance. This supports the industrial application of YAG in high-end fields such as lasers and optoelectronics.
The above process is completed using the Hemei Semiconductor Lapping and Polishing Machine
