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The Benefits and Uses of Sapphire Optical Windows

7th Dec 2018

Windows play an important role in optical systems, both in terms of maximising transmission and reducing reflection, and also in protecting optical systems and electronic sensors from everything the environment throws at them.

When environmental conditions are excessively harsh, optical windows need to up their game, and this means choosing a material that offers exceptional robustness. Step in sapphire.

Why sapphire windows?

Sapphire (Al203) is an incredibly durable crystal material, second only to diamond in the hardest natural substance ratings.

Optical components crafted from sapphire are renowned for outperforming and outlasting the likes of fused silica and quartz within a comparable transmission range.

Here’s why sapphire is a material that is in such high demand:

  • High mechanical strength in comparison to other optical materials
  • Extreme surface hardness and structural integrity
  • Exceptional resistance to abrasion and scratching
  • Extremely wide optical transmission band from UV to mid-IR
  • Ability to withstand temperatures up to 2030 degrees Celsius
  • Chemically unreactive and resistant to virtually all chemicals except very hot caustics
  • High thermal conductivity, outperforms copper at cryogenic temperatures

What are sapphire windows used for?

Due to their high structural strength, sapphire optical windows can be made a great deal thinner than other optical windows, which results in improved transmission. Sapphire optical windows are useful through a wide wavelength range of 0.15 to 5.5µm and are resistant to UV radiation darkening.

Applications where the likes of high temperature, high pressure, high thermal loads, scratch and wear resistance, corrosive atmospheres and low friction must be taken into consideration all lend themselves to sapphire windows. Furnace viewports, submersible ROVs, gas and oil analysis, barcode readers and IR analytical devices all typically use sapphire windows.

Industry-wise, the military and defence, space, medical and research sectors will naturally gravitate towards sapphire windows due to their exceptionally superior performance and reliability in mission critical applications.

Sapphire Windows from Knight Optical

Knight Optical supplies a wide range of sapphire windows, lenses, prisms and blanks both from stock and custom made to suit individual specifications. You can select from random polarisation sapphire for any application other than UV, or C-cut or Z-cut for UV applications.

Tailored advice is available from our helpful multilingual technical sales team. Call 01622 859444 or [email protected].

For full technical specifications on our range of toughened windows please visit