LBO Non-linear (NLO) Crystal
- Lithium Triborate (LiB3O5, LBO)
- LBO Crystal (Lithium Triborate, LiB3O5) is an inorganic crystal composed of lithium, boron, and oxygen, and is a material with non-linear optical (NLO) properties. It is mainly used in laser technology for second harmonic generation (SHG), sum frequency generation (SFG), and optical parametric oscillation (OPO).
Features
- Wide transmission range from 160 nm to 2600 nm
- High optical homogeneity (dn»10-6/cm), free from impurities
- elatively large efficient SHG coefficient (about 3 times that of KDP)
- High damage threshold
- Wide acceptance angle and small walk-off
- Non-critical phase matching (NCPM) in Type I and Type II over a wide wavelength range (spectral NCPM around 1300 nm)
Main Uses
- SHG (Second Harmonic Generation): Generating 532 nm green light with lasers such as Nd:YAG.
- OPO (Optical Parametric Oscillation): Used as a wavelength-variable light source in the infrared region.
- Ultraviolet light generation: Utilized in high-order harmonic generation (HHG) and other wavelength conversion processes.
- LBO crystals play a central role in advanced applications in laser technology, and due to their high efficiency and durability, they are widely used in scientific research and industrial applications.
Chemical and Structural Properties
| Crystal Structure | Orthorhombic, Space group Pna21, Point group mm2 |
|---|---|
| Lattice Parameter | a = 8.4473 Å, b = 7.3788 Å, c = 5.1395 Å, Z = 2 |
| Melting Point | About 834℃ |
| Mohs Hardness | 6 |
| Density | 2.47 g/cm3 |
| Thermal Conductivity | 3.5 W/m/K |
| Thermal Expansion Coefficient | ax = 10.8 × 10-5/K, ay = -8.8 × 10-5/K, az = 3.4 × 10-5/K |
Optical and Nonlinear Optical Characteristics
| Transparency Range | 160 - 2600 nm |
|---|---|
| SHG Phase Matchable Range | 551 - 2600 nm (Type I) 790 - 2150 nm (Type II) |
| Therm-optic Coefficient (℃, λ in µm) |
dnx/dT = -9.3 × 10-6 dny/dT = -13.6 × 10-6 dnz/dT = (-6.3 - 2.1λ) × 10-6 |
| Absorption Coefficient | <0.1%/cm at 1064 nm <0.3%/cm at 532 nm |
| Angle Acceptance | 6.54 mrad-cm (φ, Type I, 1064 SHG) 15.27 mrad-cm (θ, Type II, 1064 SHG) |
| Temperature Acceptance | 4.7℃-cm (Type I, 1064 SHG) 7.5℃-cm (Type II, 1064 SHG) |
| Spectral Acceptance | 1.0 nm-cm (Type I, 1064 SHG) 1.3 nm-cm (Type II, 1064 SHG) |
| Walk-off Angle | 0.60° (Type I 1064 SHG) 0.12° (Type II 1064 SHG) |
| NLO Coefficients |
deff(I) = d32cosΦ (Type I in XY plane) deff(I) = d31cos2θ + d32sin2θ (Type I in XZ plane) deff(II) = d31cosθ (Type II in YZ plane) deff(II) = d31cos2θ + d32sin2θ (Type II in XZ plane) |
| Non-vanished NLO susceptibilities |
d31= 1.05 ± 0.09 pm/V d32= -0.98 ± 0.09 pm/V d33= 0.05 ± 0.006 pm/V |
| Sellmeier Equations (λ in µm) |
nx2 = 2.454140 + 0.011249 / (λ2 - 0.011350) - 0.014591λ2 - 6.60 × 10-5λ4 ny2 = 2.539070 + 0.012711 / (λ2 - 0.012523) - 0.018540λ2 + 2.0 × 10-4λ4 nz2 = 2.586179 + 0.013099 / (λ2 - 0.011893) - 0.017968λ2 - 2.26 × 10-4λ4 |