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Knight Optical(UK) Ltd - - +44 (0)1622 859444

Borosilicate or equivalent windows

What are you looking for in Stock?

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.

Material: Borosilicate (LEGB) or equivalent
Diameter: +0, -0.2mm
Dimensions: ±0.3mm
Thickness ±0.2mm (float)
±0.1mm (polished)
Float type (typical) 1λ over 10mm dia
Polished grade λ/2 over 90% of aperture
Surface quality:  
Float type (typical) < 60:40 Scratch/Dig
Polished grade < 40:20 Scratch/Dig
Parallelism: <1 arc minute (polished type)


  • 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.

Stock Optics

Get a Custom Quote

Part No. GradeCoatingDiameter
WGP1000 FloatUncoated101.1 £5.75
WGP100100 FloatUncoated1001003.3 £13.60
WGP1600 FloatUncoated161.1 £5.95
WGP2500 FloatUncoated251.1 £7.25
WGP4000 FloatUncoated401.1 £7.35
WGP5000 FloatUncoated501.1 £8.25
WGP5011 FloatUncoated503.3 £11.00
WGP5051 FloatUncoated50503.3 £10.40
WHP1000 Optically polishedUncoated102 £8.15
WHP1500 Optically polishedUncoated152 £8.15
WHP1600 Optically polishedUncoated163 £8.15
WHP2500 Optically polishedUncoated253 £9.25
WHP2511 Optically polishedUncoated252 £8.40
WHP4000 Optically polishedUncoated403 £14.65
WHP5000 Optically polishedUncoated505 £17.45
WHP5050 Optically polishedUncoated50502 £17.45
WGP5500 FloatUncoated556 £6.75
WGP2540 FloatUncoated40251.1 £7.50
WGP2501-AV2 FloatDouble sided AR 400-1000nm251.1 £9.45
WGP2500-AV2 FloatSingle sided AR 400-1000nm251.1 £8.95
WGP5050-AV2 FloatSingle sided AR 400-1000nm50501.1 £13.45
WGP1001-AV2 FloatDouble sided AR 400-1000nm1001001.1 £33.50
WGP1000-AV2 FloatSingle sided AR 400-1000nm1001001.1 £48.00
WGP5051-AV2 FloatDouble sided AR 400-1000nm50501.1 £14.95

Get a Custom Quote

Get in touch

Our Multi-Lingual Sales Team are here to help with your requirments:

UK +44 (0)1622 859444
UK +44 (0)1622 850614
UK +44 (0)1622 851078
+1 401 583 7846

International Shipping

We are able to ship to most countries at good rates, please click here for more info.

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