BBO Non-linear (NLO) Crystal
- Beta-Barium Borate (β-BaB2O4 or BBO)
- BBO crystal (Beta-Barium Borate, β-BaB2O4) is an advanced optical material used for efficient wavelength conversion over a wide range of wavelengths, possessing Nonlinear Optical (NLO) characteristics.
Features
- Broad phase-matching range from 409.6 nm to 3500 nm
- Wide transmission range from 190 nm to 3500 nm
- About 6 times larger SHG conversion efficiency than KDP crystal
- High damage threshold - high optical homogeneity with dn»10-6/cm
- Broad temperature range of about 55℃
Main Applications
- Second Harmonic Generation (SHG)
- Generates green or ultraviolet light using Nd:YAG laser (1064 nm → 532 nm) or Titanium Sapphire laser (800 nm → 400 nm).
- Sum Frequency Generation (SFG) and Difference Frequency Generation (DFG)
- Used for a wide range of wavelength-variable infrared sources and other special wavelength generation processes.
- Optical Parametric Oscillation (OPO) and Optical Parametric Amplification (OPA)
- Used in research and industrial applications where wavelength variability is important.
- High Harmonic Generation (HHG)
- Particularly used in the generation of short-wavelength ultraviolet (UV) and X-rays.
- Industrial and Medical Fields
- Used in precision laser processing, non-destructive inspection, and medical laser systems.
- BBO crystals are widely used as indispensable materials in high-power laser systems and scientific research fields, providing performance that cannot be achieved with conventional materials due to their excellent optical properties.
Chemical and Structural Properties
| Crystal Structure | Trigonal, space group R3c |
|---|---|
| Lattics Parameters | a = b = 12.532 Å, c = 12.717 Å, Z = 6 |
| Melting Point | About 1095℃ |
| Mohs Hardness | 4 |
| Density | 3.85 g/cm3 |
| Thermal Conductivity | 1.2 W/m/K(┴c): 1.6 W/m/K(//c) |
| Thermal Expansion Coefficients | α11 = 4 × 10-6/K; α33 = 36 × 10-6/K |
Optical and Nonlinear Optical Properties
| Transparency Range | 190-3500 nm |
|---|---|
| SHG Phase Matchable Range | 409.6-3500 nm (Type I) 525-3500 nm (Type II) |
| Therm-optic Coefficient (/℃) |
dno/dT = -16.6 × 10-6 dne/dT = -9.3 × 10-6 |
| Absorption Coefficients | <0.1%/cm at 1064 nm <1%/cm at 532 nm |
| Angle Acceptance | 0.8 mrad-cm (θ, Type I,1064 SHG) 1.27 mrad-cm (θ, Type II,1064 SHG) |
| Temperature Acceptance | 55℃-cm |
| Spectral Acceptance | 1.1 nm-cm |
| Walk-off Angle | 2.7° (Type I 1064 SHG) 3.2° (Type II 1064 SHG) |
| NLO Coefficients |
deff (I) = d31sinθ + (d11cos⌀-d22sin3⌀) cosθ deff (II) = (d11sin3⌀ + d22cos3⌀) cos2θ |
| Non-vanished NLO susceptibilities |
d11 = 5.8 × d36(KDP) d31 = 0.05 × d11 d22 < 0.05 × d11 |
| Sellmeier Equations (λ in µm) |
no2 = 2.7359 + 0.01878 / (λ2-0.01822) -0.01354λ2 ne2 = 2.3753 + 0.01224 / (λ2-0.01667) -0.01516λ2 |
| Electro-optic Coefficients | r22 = 2.7 pm/V |
| Half-wave Voltage | 7 KV (at 1064 nm, 3 × 3 × 20 mm3) |
| Resistivity | >1011 ohm-cm |
| Relative Dielectric Constant |
εs11/εo:6.7 εs33/εo:8.1 Tan δ<0.001 |