Yb:YAG (Ytterbium-Doped Yttrium Aluminum Garnet) Single Crystal

Advantages

• Low quantum defect and reduced thermal load: The small energy difference between pump (940 nm) and laser (1030 nm) photons results in a quantum defect of less than 10%, reducing heat generation by a factor of 3-4 compared with Nd:YAG under equivalent pump power . This makes Yb:YAG the preferred gain medium for high-power and high-energy laser systems.
• Broad and simple electronic structure: Yb³⁺ possesses only two electronic manifolds (²F₅/₂ and ²F₇/₂), eliminating excited-state absorption (ESA), upconversion, and concentration quenching effects that limit other rare-earth-doped crystals . This enables high doping concentrations without degradation of laser performance.
• Wide absorption bandwidth: The 940 nm absorption band has a full width at half maximum of approximately 18 nm, eliminating the need for precise temperature control of pump laser diodes.
• Long upper-state lifetime: Fluorescence lifetime of approximately 1.0-1.3 ms, roughly four times longer than Nd:YAG, enabling efficient energy storage for Q-switched and pulsed laser operation.
• Broad emission bandwidth: Emission linewidth of approximately 9 nm supports ultrashort pulse generation, with sub-picosecond pulses achievable in mode-locked configurations.
• Excellent thermo-mechanical properties: High thermal conductivity (14 W/(m·K) at 20°C), high fracture strength, and Mohs hardness of 8.5 enable reliable operation under high thermal loads.

Typical Specifications

• Chemical formula: Yb³⁺:Y₃Al₅O₁₂
• Crystal structure: Cubic garnet, space group Ia3d
• Lattice constant: a = 12.01 Å
• Yb doping concentration: 0.5–30 at.% (standard commercial range: 1-10 at.%)
• Laser transition: ²F₅/₂ → ²F₇/₂
• Laser wavelength: 1030 nm (primary); tunable 1020–1060 nm
• Pump wavelength: 940 nm or 969 nm
• Pump absorption bandwidth: ~18 nm at 940 nm
• Absorption cross-section: 8.2 × 10⁻²¹ cm² @ 941 nm
• Emission cross-section: 2.1 × 10⁻²⁰ cm² @ 1030 nm
• Fluorescence lifetime: ~1.0–1.3 ms
• Emission linewidth: ~9 nm
• Refractive index: 1.82 @ 1030 nm
• Density: 4.56 g/cm³
• Melting point: 1970 °C
• Mohs hardness: 8.5
• Thermal conductivity: 14 W/(m·K) @ 20°C; 10.5 W/(m·K) @ 100°C
• Thermal expansion coefficient: 7.7–8.2 × 10⁻⁶/K (orientation-dependent)
• Thermo-optic coefficient: 7.3 × 10⁻⁶/K
• Damage threshold: ≥1 GW/cm² @ 1064 nm, 10 ns, 10 Hz

Standard Fabrication Specifications

• Orientation: <111>, <100>, or <110> ± 0.5°
• Diameter: 1–50 mm
• Length: 5–150 mm
• Dimension tolerance: Φ: +0/−0.1 mm; L: +0.5/−0 mm
• Perpendicularity: ≤5 arc min
• Parallelism: ≤10 arc sec
• Clear aperture: ≥95%
• Surface quality: 10/5 Scratch/Dig
• Surface flatness: ≤λ/10 @ 632.8 nm
• Wavefront distortion: ≤λ/8 per inch @ 632.8 nm
• AR coating: R < 0.15% @ 1030 nm

Main Applications

• High-power thin-disk lasers: Yb:YAG is the gain medium of choice for thin-disk laser systems, with CW output exceeding 1 kW demonstrated in dual-rod configurations . The low quantum defect and efficient thermal management make Yb:YAG ideal for industrial cutting, welding, and drilling applications.
• Picosecond and femtosecond pulse amplification: Yb:YAG is widely used in chirped-pulse amplification (CPA) systems for high-energy, high-repetition-rate picosecond lasers, particularly for industrial micromachining and scientific research.
• Q-switched microchip lasers: Compact Yb:YAG/Cr⁴⁺:YAG passively Q-switched microchip lasers have demonstrated 0.4 mJ pulses at 1030 nm with 350 ps pulse width and 1.1 MW peak power.
• Cryogenic high-energy lasers: At cryogenic temperatures (77 K), thermal conductivity increases by a factor of 9, saturation fluence decreases to 1.7 J/cm², enabling efficient energy extraction for high-energy laser fusion drivers.