Barium Borate (a-BBO) Crystal
High Temperature
form BBO (a-BaB2O4)
is a negative uniaxial crystal. It has large birefringence
over the broad transparent range from 189 nm to 3500 nm.
Recently, CASIX has succeeded in growing this crystal
into large size. The physical, chemical, thermal and optical
properties of a-BBO crystal are similar to those of b-BBO.
However, the nonlinear optical properties of a-BBO crystal
is vanished due to the centric symmetry with its crystal
structure. It is not recommended to use for NLO processes.
a-BBO
is an excellent crystal to replace Calcite, TiO2,
and LiNbO3, etc. in Glan-Taylor
and Glan-Thompson polarizers as well as walk-off beam
splitters, especially for high power and UV polarizer,
due to its unique UV transparency, good mechanical properties
and high damage threshold. CASIX manufactures and supplies
Glan-Laser, Glan-Taylor, Glan-Thompson Polarizers and
other beam displacers from high quality a-BBO
crystals to replace Calcite in many applications, especially
in UV and high power operations.
1. Basic Properties of a-BBO
| Transparency
Range: 189 - 3500 nm, See Transparency Curve |
Transparency Curve of a-BBO |
| Density: 3.85 g/cm3 | |
| Therm-Optic
Coefficients: dno/dT = -9.3 x 10-6/oC dne/dT = -16.6 x 10-6/oC |
|
| Damage
Threshold at 1064 nm 1GW/cm2 at 355 nm 500 MW/cm2 |
|
| Optical Homogeneity:Dn » 10-6/cm | |
| Mohs Hardness: 4.5 | |
| Hygroscopic Susceptibility:Low | |
| Thermal
Expansion Coefficients (in the range of 25oC – 900oC) |
aa=
4 x 10-6/K ac= 36 x 10-6/K |
Linear Absorption Coefficients: a <0.005 cm-1 from 300 nm to 2300 nm |
|
| Refractive
Indices, Birefringence (Dn
= ne - no) and Walk-off Angle
at 45o (r): at 1.0642 mm ne= 1.5379, no = 1.6579 Dn =-0.073282 r =-4.9532° at 0.5321 mm ne = 1.5534, no = 1.6776 Dn =-0.075491 r =-5.0407° at 0.2660 mm ne = 1.6114, no = 1.7617 Dn=-0.089805 r =-5.6926° |
|
2. Specifications of a-BBO
Surface Quality |
20/10 Scratch and Dig |
Beam Deviation |
<3 arc min. |
Optical Axis Orientation |
+/-0.5° |
Flatness |
l/4 @ 632.8 nm |
Transmission Wavefront Distortion |
<l /2 @632.8 nm |
AR-coating |
R<0.5% |
3. Applications of a-BBO
Please refer to Polarizer for the applications of a-BBO.