Beta-Barium Borate (β-BaB₂O₄), commonly known as BBO, is one of the most important nonlinear optical crystals for ultraviolet and visible laser applications. It is renowned for its wide transparency range, high laser damage threshold, large nonlinear optical coefficients, and excellent phase-matching flexibility.
BBO is widely used in high-power and ultrafast laser systems for frequency doubling, tripling, sum-frequency generation, and optical parametric oscillation, as well as in advanced scientific and quantum-optics applications.
Physical & Mechanical Properties
| Parameter | Value |
|---|---|
| Density | 3.85 g·cm⁻³ |
| Melting Point | 1095 °C |
| Mohs Hardness | 4 |
| Thermal Conductivity | 1.2 W·m⁻¹·K⁻¹ (⊥ c-axis) 1.6 W·m⁻¹·K⁻¹ (‖ c-axis) |
| Crystal Structure | Trigonal System |
| Lattice Constants | a = b = 12.532 Å, c = 12.717 Å |
Optical & Nonlinear Properties
| Parameter | Value |
|---|---|
| Transparency Range | 190 – 3500 nm |
| SHG Phase-Matchable Range | 409.6 – 3500 nm (Type I) 525 – 3500 nm (Type II) |
| Thermal-Optic Coefficient | dnₒ/dT = 16.6 × 10⁻⁶ K⁻¹ dnₑ/dT = 9.3 × 10⁻⁶ K⁻¹ |
| Absorption Coefficient | < 0.1% @1064 nm < 1% @532 nm |
| Angle Acceptance | 0.8 mrad·cm⁻¹ (Type I, 1064 nm SHG) 1.27 mrad·cm⁻¹ (Type II, 1064 nm SHG) |
| Temperature Acceptance | 55 °C·cm⁻¹ |
| Spectral Acceptance | 1.1 nm·cm⁻¹ |
| Walk-off Angle | 2.7° (Type I, 1064 nm SHG) 3.2° (Type II, 1064 nm SHG) |
Nonlinear Optical Coefficients
- Effective SHG coefficient: ~6× that of KDP
- Non-vanishing susceptibilities:
d₁₁ = 5.8 × d₃₆ (KDP)
d₃₁ < 0.05 × d₁₁
d₂₂ < 0.05 × d₁₁
Electro-Optic & Electrical Properties
| Parameter | Value |
|---|---|
| Electro-Optic Coefficient | r₂₂ ≈ 2.7 pm·V⁻¹ |
| Half-Wave Voltage | ~7 kV (@1064 nm, 3 × 3 × 20 mm³) |
| Resistivity | > 10¹¹ Ω·cm |
| Relative Dielectric Constant | ε₁₁ ≈ 6.7 ε₃₃ ≈ 8.1 |
| Dielectric Loss | tan δ < 0.001 |
Standard Manufacturing Specifications
| Item | Specification |
|---|---|
| Dimension Tolerance | W × H ±0.1 mm, L +0.5 / −0.1 mm |
| Angular Tolerance | Δθ ≤ 0.25°, Δφ ≤ 0.25° |
| Parallelism | < 20 arc sec |
| Perpendicularity | < 5 arc min |
| Chamfer | 0.1 mm × 45° |
| Clear Aperture | ≥ 90% |
| Scratch & Dig | 20/10 |
| Surface Flatness | λ/8 @ 633 nm |
| Wavefront Distortion | λ/8 @ 633 nm |
| Damage Threshold | >0.5 GW·cm⁻² (@1064 nm, TEM₀₀, 10 ns, 10 Hz) >0.3 GW·cm⁻² (@532 nm, TEM₀₀, 10 ns, 10 Hz) |
Key Advantages
- Extremely wide transparency range, extending into deep UV
- Very high SHG efficiency, ~6× KDP
- High laser damage threshold for pulsed and high-power lasers
- Flexible Type I and Type II phase matching
- Excellent optical homogeneity for precision applications
- Widely proven in scientific, industrial, and quantum optics systems
Typical Applications
- Frequency Doubling & Tripling: UV generation (266 nm, 355 nm) from Nd:YAG and ultrafast lasers
- Optical Parametric Oscillators (OPOs): Broad tunability from UV to near-IR
- Quantum Optics & SPDC: Photon-pair generation and entanglement experiments
- High-Precision Laser Processing: Micromachining, spectroscopy, and photochemistry
- Electro-Optic Applications: Q-switching and modulation in high-power laser systems
Shape Optics Capabilities
Shape Optics supplies high-quality BBO crystals for research, industrial, and OEM laser systems.
Available Configurations
- Maximum size: up to 15 × 15 × 15 mm
- Thickness / length: 0.02 – 25 mm
- Crystal cut & orientation: custom on request
- Optical coatings: AR and custom coatings available
With over 20 years of experience in optical manufacturing, Shape Optics combines precision crystal processing, advanced polishing, and in-house coating capabilities across the UV–NIR spectrum. Our solutions focus on performance consistency, reliability, and full compliance with international optical standards.
For high-performance nonlinear optical solutions, contact Shape Optics to discuss your BBO crystal requirements.