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Borosilicate Window Optically Polished Grade 25mmdia x 2mthk Uncoated

SKU: WHP2511
More Information
Diameter (mm) 25
Material Borosilicate
Coating Uncoated
Thickness (mm) 2
Grade Optically polished

We offer two grades of stock borosilicate or equivalent  windows. Our standard windows are cut from float sheet material and  our polished grade is then further polished to better flatness and surface quality.

These borosilicate or equivalent windows listed here are made from low expansion borosilicate or equivalent  glass. Borosilicate has excellent transmission over the visible and NIR wavelengths working from 310nm to 2700nm. The surface quality is not as high as the BK7 versions.

Low-expansion windows are very useful in applications where they are exposed to the elements as borosilicate has excellent chemical and thermal-shock resistance and has a maximum working temperature of 500°C. Examples include use in high powered light source applications and they are an excellent choice for cold and hot mirror substrates.   Borosilicate or equivalent windows can also be a good substrate for optical flats as it has low expansion properties and therefore maintains its flatness in different environmental conditions.

Our stock windows are available to buy directly from this site, and we also offer an extensive custom window capability for unique shapes and sizes. For more information on our custom windows please contact our technical sales team.


Clear Aperture:
Float type
Polished grade

Surface quality:
Float type (typical)
Polished grade

Borosilicate (LEGB) or equivalent
±0.2mm (float)
±0.1mm (polished)

1λ over 10mm dia (not guaranteed)
<50mm-λ/2 over 90% of aperture
≥50mm-1λ over 90% of aperture

<60:40 Scratch/Dig
<40:20 Scratch/Dig
<1 arc minute (polished type)
<2% 400-1000nm (typical)

Edge down of stock windows to smaller diameters.
Stock windows can be machined to custom square/ rectangular apertures.
Mounting options.
Custom AR coatings.
Custom mirror and beamsplitter coatings can be applied to uncoated precision grade BK7 windows.
Please enquire about flatter options.