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BBO

BBO is a negative uniaxial crystal with ordinary refractive-index (no) larger than extraordinary refractive-index (ne). Both type I and type II phase-matching can be reached by angle-tuning. BBO is of particular importance in the visible and far UV range.

BBO is hygroscopic. The user is advised to provide dry conditions for both working and storage of BBO. BBO is relatively soft and therefore requires precautions to protect its polished surfaces.

When angle adjusting is necessary, keep in mind that the acceptance angle of BBO is small.

Physical properties:

Crystal Structure: | Trigonal, space group R3c |

Lattics Parameters: | a=b=12.532Å, c=12.717Å, Z=6 |

Melting point | About 1095℃ |

Mohs Hardness | 4 |

Density | 3.85g/cm3 |

Thermal Conductivity Coefficients |
⊥c: 1.2W/m/K; //c: 1.6W/m/K |

Thermal Expansion Coefficients | α_{11}=4 x 10^{-6}/K; α_{33}=36x 10^{-6}/K |

Optical Properties:

Transparency Range: | 190-3500nm |

SHG Phase Matching Range | 409.6-3500nm(Type I) 525-3500nm(Type II) |

Thermal Optic Coefficients (/℃) | dno/dT=-16.6x10^{-6}; dne/dT=-9.3x10^{-6} |

Absorption Coefficients | <0.1%/cm at 1064nm; <1%/cm at 532nm |

Angle Acceptance | 0.8mrad.cm (θ, Type I,1064 SHG) 1.27mrad.cm (θ, Type II,1064 SHG) |

Temperature Acceptance | 55℃-cm |

Spectral Acceptance | 1.1nm.cm |

Walk-off Angle | 2.7° (Type I 1064 SHG) 3.2° (Type II 1064 SHG) |

NLO Coefficients | deff (I) = d31sinθ + (d11cosΦ - d22sin3Φ) cosθ deff (II) = (d11sin3Φ + d22cos3Φ) cos2θ |

Non-vanished NLO susceptibilities | d11 = 5.8 x d36(KDP) d31 = 0.05 x d11 d22 < 0.05 x d11 |

sellmeier Equations (λ in μm ) | no^{2} = 2.7359 + 0.01878 / (λ^{2}-0.01822) -0.01354 λ^{2}ne ^{2} = 2.3753 + 0.01224 / (λ^{2}-0.01667) -0.01516 λ^{2} |

Electro-optic coefficients: | r22=2.7pm/V |

Half-wave voltage: | 7KV (at 1064nm,3*3*20mm3) |

Resistivity: | >10^{11} ohm.cm |

Relative Dielectric Constant: | ε^{s}11/εo : 6.7ε ^{s}33/εo : 8.1Tan δ < 0.001 |

Relevant NLO properties for type I BBO crystal | ||||

Fundamental wavelength: 1064nm | SHG | THG | FHG | 5HG |

Effective NLO Coefficient (d36(KDP)) | 5.3 | 4.9 | 3.8 | 3.4 |

Acceptance Angle (mrad-cm) | 1.0 | 0.5 | 0.3 | 0.2 |

Walk-off Angle (°) | 3.2 | 4.1 | 4.9 | 5.5 |

**BBO's E-O Applications**

Dimension Tolerance | W(+/-0.1)*H(+/-0.1)*L(+0.5/-0.1)mm | ||

Angle Tolerance | +/-0.25° | Perpendicularity | ≤ 10’ |

Scratch/Dig | 20/10 | Chamfer | ≤ 0.2mm x 45° |

Parallelism | ≤10″ | Chips | ≤ 0.1mm |

Flatness | λ/10@633nm | Clear Aperture | ≥ 90% |

Wavefront distortion | λ/8@633nm | ||

Coatings |
C1--- AR/AR@532(R<0.2%)&266(R<0.5%) C2--- AR/AR@1064(R<0.2%)&532(R<0.5%)&355(R<0.5%) C3--- Pcoating/Pcoating |
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Damage Threshold | 1GW/cm² (1064nm, 10ns, 10Hz) |