Brewster Windows
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Brewster windows are windows designed for use at Brewster's angle (usually uncoated). This is the angle where only incident p-polarized light has 0% transmission loss. They are an economical option for coupling linearly polarized light into sealed optical systems and to select the polarization of light traveling in optical cavities.
Brewster's angle can be calculated using the following equation:
θB=Arctan(nw/na)
Where θB is Brewster's angle and nw and na are the indices of refraction for the window and the ambient respectively. na is usually assumed to be 1 for air.
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RMI Standard Specifications
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| Materials: |
BK7, UVFS, FS, CaF2,
MgF2, BaF2, ZnSe, ZnS, Ge,
Si, Sapphire, Cleartran, Infrasil, Suprasil |
| Angle of Incidence: |
Brewster’s Angle (θB) |
Surface Figure:
BK7, UVFS, FS:
CaF2, MgF2, BaF2:
Sapphire (2 grades):
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Both Surfaces
λ/20 at 633 nm
λ/4 at 633 nm
λ/10, or λ/4 at 633 nm |
Surface Quality:
BK7, UVFS, FS:
CaF2, MgF2, BaF2:
Sapphire (2 grades):
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Both Surfaces
10-5
20-10
20-10 or 60-40 |
| Diminsional Tolerance: |
+ 0.000", – 0.010" |
| Thickness Tolerance: |
± 0.010" |
Wedge:
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Brewster ≤ 10 seconds, Elliptical ≤ 3 minutes
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| Bevels: |
0.02" at 45º typical
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| Clear Aperture: |
Exceeds Central 85% of diameter |
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