Lithium triborate (LiB3O5 or LBO) is an excellent nonlinear optical crystal. It combines a wide transparency range (210-2300 nm), moderate nonlinear coupling, relatively high damage threshold and good chemical and mechanical properties. LBO crystals have phase matchable conditions for SHG and THG of infrared lasers, using either Type I or Type II interactions.
LBO has non-critical phase matching conditions (NCFM) for Type I SHG at 1000-1300nm. In this case, LBO is free of walk-off limitations and, therefore, long LBO crystals can be used. LBO crystals are free of the grey track effect and as a result, are very useful in high power green lasers.
Physical and Chemical Properties
| Crystal Structure | Orthorhombic, Point group mm2, Space group Pna21 |
| Lattice Parameters | a=8.4473Å, b=7.3789Å, c=5.1405Å, z=2 |
| Density | 2.47 g/cm3 |
| Mohs Hardness | 5.5 |
| Melting Point | 835 ±5°C |
| Optical Homogeneity | Dn~10-6/cm |
| Absorption Coefficient | < 0.03%/cm @1.064μm, < 0.1%/cm @0.532μm |
| 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 |
| Hygroscopisity | Non |
Specifications
| Dimensional Tolerance | (W±0.1mm) x (H±0.1mm) x (L+0.2/-0.1 mm) L>2mm |
| (W±0.1mm) x (H±0.1mm) x (L±0.1 mm) L<2mm | |
| Absorption | <0.002%@1064nm, <0.01%@532nm |
| Cutting Angle Tolerance | Dq< ±0.2°, Df< ±0.2° |
| Wavefront Distortion | <λ/8 @632.8 nm |
| Chamfer | ≤ 0.15 mm x 45° |
| Perpendicularity | < 5 arc min |
| Parallelism | < 20 arc sec |
| Flatness | <λ/10 @633 nm |
| Scratch/Dig | 10/5 per MIL-PRF-13830B |
| Clear Aperture | > Central 90% |
| Antireflection Coating | R < 0.2% @1064nm,R < 0.5% @532nm,R<3%@355nm |
