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α-BBO, high temperature phase of BaB2O4, is an excellent birefringent crystal, which has been successfully grown in our laboratory. It is characterized by large birefringent coefficient and wide transmission-window ranged from 189nm to 3500nm. The high chemical stability and medium hardness of α-BBO make it easy to be fabricated into many kinds of fine optical components, such as prisms, optical isolators. Therefore, in many cases, the calcite, YVO4, TiO2 etc. can be replaced by α-BBO. Especially, compared with natural calcite crystal, whose practical applications are often limited due to its optical in-homogeneity, small size and cleavability,α-BBO has high optical quality and large size (in diameter of 40-50mm and length of 25-35mm).
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| Specifications of α-BBO |
| Diameter |
max 40~50mm |
| Length |
max 25~35mm |
| Surface Quality |
20/10 Scratch and Dig |
| Beam Deviation |
<3 arc min. |
| Optical Axis Orientation |
+/-0.5° |
| Flatness |
λ/4 @ 632.8 nm |
| Transmission Wavefront Distortion |
<λ/2 @632.8 nm |
| AR-coating |
R<0.5% |
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Basic Properties of α-BBO
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| Transparency Range: 189 - 3500 nm, See Transparency Curve |
Transparency Curve of α-BBO
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| Density: 3.85 g/cm3 |
Therm-Optic Coefficients:
dno/dT = -9.3 x 10-6/ ℃
dne/dT = -6.6 x 10-6/ ℃ |
Damage Threshold:
at 1064nm 1GW/cm2
at 355nm 500 MW/cm2 |
| Optical Homogeneity: Δn ≈10-6/cm |
| Mohs Hardness: 4.5 |
| Hygroscopic Susceptibility: Low |
| Thermal Expansion Coefficients (in the range of 25 ℃– 900 ℃): αa= 4 x 10-6/K, αc= 36 x 10-6/K |
| Linear Absorption Coefficients: α <0.005 cm-1 from 300nm to 2300nm |
Refractive Indices, Birefringence (Δn = ne - no) and Walk-off Angle at 45º (ρ):
at 1064μm ne= 1.58462, no = 1.65790 Δn =-0.073282 ρ =-4.9532º
at 532nm ne = 1.60206, no = 1.67755 Δn =-0.075491 ρ =-5.0407º
at 266nm ne = 1.67190, no = 1.76171 Δn=-0.089805 ρ =-5.6926º
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