High temperature form BBO (α -BaB2O4) are negative uniaxial crystals. They have large birefringence over a broad transparent range of 190nm to 3500nm. Casix succeeded in growing these crystals to large sizes. The physical, chemical, thermal and optical properties of α -BBO crystals are similar to those of ß -BBO. However, the nonlinear optical properties of α -BBO crystals are nonexistent due to the centric symmetry with its crystal structure. α -BBO crystals are not recommended for NLO processes.
a -BBO are excellent crystals to replace Calcite, TiO2 LiBbO3 etc. in Glan Taylor and Glan Thompson polarizers as well as walk-off beamsplitters, especially for high power and UV polarizers. This is due to their unique UV transparency, good mechanical properties and high damage threshold. Casix also manufactures and supplies Glan Laser, Glan Taylor, Glan Thompson polarizers and other beam displacers from high quality α -BBO crystals to replace Calcites in many applications, especially in UV and high power operations.
Basic Properties of α -BBO Crystals
| Transparency Range: | 190 - 3500nm, see transparency curve |
| Density: | 3.85g/cm3 |
| Therm-Optic Coefficients: | dno/dT = - 9.3X10-6/°C |
| Damage Threshold: | @1064nm 1GW/cm2 |
| Optical Homogeneity: | Δ n~10-6/cm2 |
| Mohs Hardness: | 4.5 |
| Hygroscopic Susceptibility: | Low |
Thermal Expansion Coefficients (in the range of 25°C-900°C): | aa = 4X10-6/° K ac = 36X10-6/° K |
| Linear Absorption Coefficients: | α<0.005cm-1 from 300nm to 2300nm |
Refractive Indices, Birefringence (Δne = no) and Walk-off Angle at 45° (β): | @1.0642μm ne=1.5379 no=1.6579 Δn=-0.1199 ρ=-4.287° |
Capabilities:
| Attribute | Commercial | High Precision |
| Surface Quality | 60-40 scratch and dig | 20-10 scratch and dig |
| Optical Axis Orientation | ±0.5° | ±0.2° |
| Flatness | λ/4 | λ/10 |
| Wavefront Distortion | λ/4 | λ/8 |
| AR Coating | R<0.5% (narrow band wavelength) | |
Transparency Curve of α -BBO
