YAG (Y₃Al₅O₁₂, Yttrium Aluminum Garnet) Single Crystal

Advantages

• Broad transparency range: 210–5500 nm, with particularly excellent transmission in the 4–5 μm region .
• No birefringence: YAG is optically isotropic (cubic structure), eliminating polarization-dependent effects and making it ideal for applications requiring low aberration.
• High thermal conductivity: 11–14 W/(m·K) at room temperature, approximately 10 times better than optical glasses, enabling efficient thermal management in high-power laser systems.
• Excellent mechanical properties: Mohs hardness of 8.5 and Knoop hardness of ~1215 kg/mm², providing outstanding durability and scratch resistance.
• High optical quality and chemical stability: Minimal absorption in the MWIR, excellent durability comparable to sapphire, and stable mechanical and chemical properties.
• Ideal host for rare-earth doping: Y³⁺ ions at dodecahedral sites can be substituted by Nd³⁺, Yb³⁺, Er³⁺, Ho³⁺, Tm³⁺, and other rare-earth ions, enabling a broad family of laser crystals.

Typical Specifications

• Chemical formula: Y₃Al₅O₁₂
• Crystal structure: Cubic garnet, space group Ia3d (Oₕ¹⁰)
• Lattice constant: a = 12.01 Å
• Transmission range: 210–5500 nm
• Refractive index: 1.8152–1.82 @ 1.064 μm
• Density: 4.55–4.56 g/cm³
• Mohs hardness: 8.5
• Knoop hardness: ~1215 kg/mm²
• Melting point: 1940–1970 °C
• Thermal conductivity: 11.2–14 W/(m·K) @ 20–25 °C
• Thermal expansion coefficient: 6.1–8.2 × 10⁻⁶/K (direction-dependent)
• Young‘s modulus: ~300 GPa
• Poisson’s ratio: 0.28
• Abbe number: 56
• Phonon energy: 800–860 cm⁻¹
• Band gap: ~6.5–8 eV

Main Applications

• Laser host crystals (rare-earth doped YAG): The most important application.
• Undoped YAG windows for high-energy laser systems, benefiting from high thermal conductivity and excellent MWIR transmission.
• White light generation: YAG windows produce broadband white light when pumped with ultrafast lasers, enabling femtosecond white light (continuum) generation.
• Optical substrates: YAG substrates for UV-IR optics requiring high thermal and mechanical stability .
• Laser endcaps: YAG crystals serve as ideal endcaps for doped YAG laser crystals, with diffusion bonding technology available.