FOCtek manufactures a wide range of polarizers (Glan Laser, Glan Taylor, Glan Thompson, Wollaston and Rochon) by employing birefringent crystals: a -BBO, Calcite, YVO4 and quartz. The material properties of birefringent crystals are great influence on your selection of right type polarizers.
a -BBO (high temperature phase of BaB2O4) is characterized by large birefringent coefficient and wide transmission window from 189nm to 3500nm, particularly suitable for high power UV polarizer (200-300nm).
YVO4 crystal has been widely used in fiber optical components due to its large birefringence, good physical and favorable mechanical properties. Since the crystal has high transmission from 500 to 3500 nm, it is recommended to use YVO4 polarizer for IR (up to 4000nm) online_ordering.
Crystal quartz is a natural occurring as well as synthetically grown positive uniaxial crystal that is optical active, i.e. it rotates the plane of polarization of linearly polarized input beam traveling along the crystal optic axis. Because of it's reatively low birefringence, it is not feasible to fabricate a crystal quartz Glan type polarizer but as Rochon polarizer.
Calcite is a natural minded crystal and the most common crystals for polarizers used as visible and near IR polarizers. Defect in bulk calcite are characterized by bubbles, striae, optical inhomogeneity and stress birefringence. These defects cause degradation of polarization and transmission loss due to scattering and absorption. That is why the extinction of the polarizer is not as high as synthetically grown material YVO4, a -BBO and crystal quartz.
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 a -BBO: T% vs Wavelength |
 YVO4: T% vs Wavelength |
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Comparison of main properties of the materials listed below:
| YVO4 | Calcite | a -BBO | Quartz | |
| Transparency | 400-5000nm | 350-2300nm | 189-3500nm | 200-2300nm |
| Crystal class(Uniaxial) | Positive n o =n a =n b ,n e =n c |
Negative n o =n a =n b ,n e =n c |
Negative n o =n a =n b ,n e =n c |
Positive n o =n a =n b ,n e =n c |
| Mohs hardness | 5 | 3 | 4.5 | 7 |
| Thermal Expansion Coefficient | a a =4.43x10 -6 /K a c =11.37x10 -6 /K |
a a =24.39x10 -6 /K a c =5.68x10 -6 /K |
a a =4x10 -6 /K a c =36x10 -6 /K |
a a =6.2x10 -6 /K a c =10.7x10 -6 /K |
| Hygroscopic susceptibility | Low | Low to moisture | Low | Low |
A polarizer is an important optical component that is widely used in laser systems to generate the linear polarization laser. FOCtek makes following polarizers with three materials, a -BBO, Calcite and YVO 4 , suitable for the widest spectrum and high polarization purity online_orderings.
Polarizer |
Material |
Illustration |
Properties and online_ordering |
a - BBO |
 a -BBO |
Air-spaced
Close to Brewster's Angle Cutting. Low L/A=0.8 Mounted without escape windows. For low to medium power online_ordering. |
|
a - BBO |
 a -BBO |
Air
Spaced. Close to Brewster's angle Cutting. Mounted with escape windows. Suitable for high power online_orderings. L/A=1.5 |
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Calcite |
 Calcite |
Air
Spaced wBrewster's Angle Cutting Mounted without escape windows Suitable for high power and high transmission online_ordering Brewster Angle input |
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a - BBO |
 a -BBO |
Cemented.
Suitable for low power online_orderings. Wide acceptance angle. |
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a - BBO |
 a -BBO |
Cemented.
Separate ordinary and extraordinary beams at certain angle. Suitable for low power online_ordering and where the large deviation is required. |
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Calcite |
 Calcite |
Cemented.
Separate ordinary and extraordinary beams at certain angle. Suitable for low power online_ordering and where the large deviation is required. |
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a - BBO |
 a -BBO |
a -BBO is used to guarantee a wide transmission range. Especially, suitable for UV online_ordering. Split the ordinary and extraordinary ray, but only ordinary beam is deviated. |
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BK7 Grade A Optical Glass |
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Split the ordinary and extraordinary ray. The ordinary beam is deviated 90°Refer to chapter "Beamsplitter" For detailed information. |