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BBO (β-BaB2O4) Nonlinear Crystal for UV Harmonic Generation, 190–3500 nm
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Beta-barium borate (β-BaB2O4, BBO) is a negative uniaxial nonlinear crystal in which both Type I and Type II phase matching are reached by angle tuning. It transmits from 190 nm to 3500 nm and is used for the second, third, fourth and fifth harmonics of Nd:YAG lasers, including 5HG at 213 nm, as well as for frequency doubling of ultrafast lasers. Its electro-optic coefficient also makes it suitable for Pockels cells and EO Q-switches.
Key Features
- Transparency range 190–3500 nm
- SHG phase-matching range 409.6–3500 nm (Type I) and 525–3500 nm (Type II)
- Effective SHG coefficient about 6 times that of KDP
- Reported Nd:YAG conversion efficiencies above 70% (SHG), 60% (THG) and 50% (4HG)
- Optical homogeneity δn ≈ 10⁻⁶ /cm
- Temperature acceptance 55 °C·cm for 1064 nm SHG
- Damage threshold above 1 GW/cm² at 1064 nm, 10 ns, 10 Hz (polished, uncoated)
- Slightly hygroscopic and relatively soft (Mohs 4): use and store dry, and protect polished faces
Typical Applications
- Second, third and fourth harmonic generation of Nd:YAG lasers (532, 355 and 266 nm)
- Fifth harmonic generation of Nd:YAG lasers at 213 nm
- Intracavity SHG of high-power Q-switched Nd:YAG lasers
- Frequency doubling of ultrafast Ti:sapphire (800 nm) and Yb (1030 nm) lasers with thin crystals
- Electro-optic Pockels cells and Q-switches
Dispersion (Sellmeier) Equations
no² = 2.7359 + 0.01878 / (λ² − 0.01822) − 0.01354 λ² (λ in µm)
ne² = 2.3753 + 0.01224 / (λ² − 0.01667) − 0.01516 λ² (λ in µm)
Standard Sizes
| Size | Cut / orientation | Surface / coating | Mount |
|---|---|---|---|
| 10 × 10 × (0.01 + 1) mm | θ = 37° | Blank | Mounted |
| 5 × 5 × 0.07 mm | θ = 29.2° | Polished, uncoated | Mounted |
| 10 × 10 × 0.1 mm | θ = 29.2° | Polished, uncoated | — |
| 10 × 10 × 0.5 mm | θ = 29.2° | P-coated @ 800 + 400 nm | Mounted |
| 5 × 5 × 1 mm | θ = 51.2°, Type I | S1/S2: P-coated @ 350 nm | — |
| 5 × 5 × 3 mm | θ = 51.2°, Type I | S1/S2: P-coated @ 350 nm | — |
| 5 × 5 × 5 mm | θ = 51.2°, Type I | S1/S2: P-coated @ 350 nm | — |
| Ø10 × 0.1 mm | θ = 29.2° | P-coated @ 800 + 400 nm | Mounted |
| 10 × 6 × 0.1 mm | θ = 29.2° | P-coated @ 800 + 400 nm | Mounted |
| 10 × 3 × 0.1 mm | θ = 29.2° | P-coated @ 800 + 400 nm | Mounted |
| 10 × 10 × 0.3 mm | θ = 29.2° | P-coated @ 800 + 400 nm | Mounted |
| 10 × 10 × 1 mm | θ = 23.4°, Type I | S1/S2: P-coated @ 1030 + 515 nm | Mounted |
| Ø7 × 0.2 mm | θ = 29.2° | P-coated @ 800 + 400 nm | Mounted |
| Ø8 × 0.5 mm | θ = 28.8°, Type II | S1: P-coated @ 1400 nm; S2: P-coated @ 800 nm | Mounted |
| Ø8 × 0.5 mm | θ = 19.8°, Type I | S1: P-coated @ 1400 nm; S2: P-coated @ 800 nm | Mounted |
| Ø8 × 3 mm | θ = 19.8°, Type I | S1: P-coated @ 1400 nm; S2: P-coated @ 800 nm | Mounted |
Availability of individual sizes changes; custom sizes, cut angles and coatings are available on request.
Related Products
- LBO Crystal — high-power SHG and THG
- BIBO Crystal — larger deff
- KTP Crystal — 1064 nm SHG
Browse all: BBO Crystals · Nonlinear Crystals
Model: WQ-NLC-BBO · Custom sizes, orientations and coatings on request — contact WaveQuanta for a quote and lead time.
| Chemical Formula | β-BaB2O4 |
| Crystal Structure | Trigonal, space group R3c |
| Lattice Parameters | a = b = 12.532 Å, c = 12.717 Å, Z = 6 |
| Melting Point | About 1095 °C |
| Mohs Hardness | 4 |
| Density | 3.85 g/cm³ |
| Thermal Expansion Coefficients | α11 = 4 × 10⁻⁶ /K; α33 = 36 × 10⁻⁶ /K |
| Thermal Conductivity | ⊥c: 1.2 W/m/K; ∥c: 1.6 W/m/K |
| Transparency Range | 190–3500 nm |
| SHG Phase-Matching Range | 409.6–3500 nm (Type I); 525–3500 nm (Type II) |
| Thermo-Optic Coefficients | dno/dT = −16.6 × 10⁻⁶ /°C; dne/dT = −9.3 × 10⁻⁶ /°C |
| Absorption Coefficients | < 0.1%/cm at 1064 nm; < 1%/cm at 532 nm |
| Angular Acceptance | 0.8 mrad·cm (θ, Type I, 1064 nm SHG); 1.27 mrad·cm (θ, Type II, 1064 nm SHG) |
| Temperature Acceptance | 55 °C·cm |
| Spectral Acceptance | 1.1 nm·cm |
| Walk-off Angle | 2.7° (Type I, 1064 nm SHG); 3.2° (Type II, 1064 nm SHG) |
| Effective Nonlinear Coefficient | deff(I) = d31 sinθ + (d11 cos3φ − d22 sin3φ) cosθ; deff(II) = (d11 sin3φ + d22 cos3φ) cos²θ |
| Nonlinear Coefficients | d11 = 5.8 × d36(KDP); d31 = 0.05 × d11; d22 < 0.05 × d11 |
| Electro-Optic Coefficient / Half-Wave Voltage | γ22 = 2.7 pm/V; 7 kV at 1064 nm (3 × 3 × 20 mm³) |
| Optical Homogeneity | δn ≈ 10⁻⁶ /cm |
| Dimension Tolerance | (W ± 0.1 mm) × (H ± 0.1 mm) × (L +0.5/−0.1 mm) for L ≥ 2.5 mm; (W ± 0.1 mm) × (H ± 0.1 mm) × (L ± 0.1 mm) for L < 2.5 mm |
| Clear Aperture | Central 90% of the diameter; no visible scattering paths or centers under 50 mW green laser inspection |
| Flatness / Transmitted Wavefront Distortion | < λ/8 @ 633 nm |
| Scratch/Dig | 10/5 per MIL-PRF-13830B |
| Parallelism / Perpendicularity | ≤ 20 arcsec / ≤ 5 arcmin |
| Chamfer / Chip | ≤ 0.2 mm × 45° / ≤ 0.1 mm |
| Angle Tolerance | ≤ 0.25° |
| Damage Threshold | > 1 GW/cm² at 1064 nm, TEM00, 10 ns, 10 Hz (polished only); > 0.5 GW/cm² at 1064 nm (AR-coated); > 0.3 GW/cm² at 532 nm (AR-coated) |
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