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AR Coated Windows
Windows are frequently used in optical systems to separate the environment in one part of the system from another, such as to seal vacuum or high-pressure cells. Because the infrared transmitting material has a high index of refraction, an anti-reflection coating is typically applied to windows to minimize losses due to reflections.
For guidelines about calculating the proper thickness for a window to withstand a given pressure, see our Pressure Loading tutorial.
Below is the typical transmission of an AR coated, ZnSe window at 0° incidence:
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Diameter: +0.000”-0.005”
Thickness: +0.005“-0.010”
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Edge Thickness Variation (ETV)
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Clear Aperture (polished)
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Surface Figure (power/irregularity) at 0.63µm
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AR Coating Reflectivity per Surface at 10.6µm
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185217
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568604
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162879
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457172
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735199
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617035
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834076
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184651
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883636
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243559
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616847
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AR coated windows are available in other substrates and as uncoated windows. We also offer AR coatings at other wavelengths or wavelength bands. Contact a II-VI sales representative for exact specifications.
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Brewster Windows
Rectangular Brewster windows are uncoated substrates used in an optical system at Brewster’s Angle, the angle at which p reflectance drops to zero. This can be calculated from:
ΘB = tan-1(n)
where ΘB is Brewster’s Angle and n is the material’s index of refraction. When used in a laser cavity, a Brewster Window causes polarized laser output.
Fixed beam polarization is often required so that optical components in the system perform consistently as designed. Since many optics and coatings are polarization sensitive, a laser with a time varying polarization state can cause fluctuations in system performance.
While virtually all of the p component of polarization is transmitted by a Brewster Window, most of the s component is reflected. For ZnSe, 50% of the incident s-polarized light is reflected per surface. Ge, with a higher index of refraction, has an approximately 87% fresnel reflection of the s-polarization component at 10.6µm.
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Dimensional Tolerances
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Width
Length
Thickness
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+0.000”-0.005”
+0.000”-0.005”
+0.005”-0.010”
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Parallelism
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Plano
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Clear Aperture (polished)
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Surface Figure at 0.63µm
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Width
Length
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Power: 1 fringe per inch; Irregularity: fringe per inch
Power: 1 fringe per inch; Irregularity: fringe per inch
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Scratch-Dig
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Brewster Angle at 10.6µm
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ZnSe
Ge
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746216
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282837
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154022
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749878
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768646
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761688
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134369
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723434
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260345
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ZnSe protective window
Ge protective window
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Protective Windows
To protect scan lenses from backsplatter and other workplace hazards, II-VI offers protective windows -- also known as debris windows -- that are either included as the overall scan lens assembly part, or sold separately. These plano-plano windows are available in both ZnSe and Ge materials and also supplied mounted or unmounted.
ZnSe protective windows feature our standard AR or DAR coating. Ge protective windows feature either our standard AR coating, or an optional diamond-like carbon coating (DLC) designed to withstand the most severe conditions likely to be encountered in industrial operations.
Below are common protective window sizes.
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290025
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185594
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355172
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139647
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774352
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221234
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425225
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221345
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505791
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