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Sapphire Windows

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Sapphire Windows for Demanding Applications

A sapphire window is ideal for use under demanding conditions and in harsh, stringent environments. Sapphire is the hardest material in the world other than diamond, and exhibits resistance to many chemical acids and alkalis.  It also has very good scratch resistance, a high dielectric constant, and high thermal conductivity.

Shanghai Optics uses single crystal to manufacture high quality sapphire windows and precision optical components, and because of sapphire’s high mechanical strength we are able to make these optical windows much thinner and with better transmittance than other dielectric windows.  Uncoated sapphire transmits best between 170 nm and 5.5 µm. We are able to provide custom windows to meet any specification, and our design team would be happy to discuss your application and help you come up with an optical solution that best suits your needs.

Sapphire Windows in Extreme Temperature Environments

Sapphire’s maximum temperature rating of almost 2000 ° C makes it ideal for lamp shields, high temperature combustion chambers, furnace systems, and gas processing. A supported sapphire window remains at peak performance up to 1700 ° C and may reach 1950 C with absolutely no change to its shape and only the very slightest decrease in optical performance.

Sapphire is unique among optical material in this regard. The next best option, fused silica, will begin to degrade at temperatures of 1000 ° C and melts completely at 1650 °C.

Other Benefits of Sapphire Windows

Sapphire is inert in the presence of molten metal, acids, and all caustic agents with the sole exception of hot caustic salts. This makes sapphire an ideal choice for plasma chambers, sapphire lamps, and other situations where heat and corrosive chemicals would destroy any other optical substrate. Their chemical inertness also makes them a good choice for medical and pharmaceutical applications, where maintaining purity of the surrounding substances is key.

The structural strength of sapphire also makes it suitable for a wide range of applications where high pressures would compromise other optics; for instance, in aircraft sensors, deep sea windows, or sight windows on pressurized experiment vessels.

Since sapphire is highly resistant to scratches it provides consistently optical clarity even under abrasive conditions or under exposure to sand and grit that would ruin any other optic. This makes it ideal for optical windows on smart phone cameras, for gun sights, and for downhole and drilling vision systems.

Sapphire transmits well in both UV and IR ranges. As with all optical materials, the thinner the window the deeper into the UV and IR it transmits, and our ultra-thin sapphire windows offer very deep transmittance.

The Knoop hardness of sapphire is 1900 GPa, and the density 3.97 g/cm3. The index of refraction is 1.77 at 500 nm, and the Abbe number 72.74 vd.

[Sapphire Window Production - Shanghai Optics]

Shanghai Optics in-house facility are capable of handling custom-made sizes and coating material for Sapphire optical windows for wide variety of applications.

Shanghai Optics Sapphire Window Specifications

Our factory standard involves a clear aperture of at least 90 percent of diameter, and a surface quality of 80-50 scratch dig. Birefringence is 0.008 for visible light in directions to the optic axis, and crystal axis cut is random. We can provide c-cut and tighter surface quality specifications on request.

Factory Standard 

  • Material: Optical Sapphire (Al2O3)
  • Dimension: +0, -0.2mm
  • Surface Flatness: 1λ per 25 mm at 633 nm over clear aperture
  • Surface Quality: 80-50 scratch and dig, beveled edges
  • Crystal axis cut: random (c-cut available upon request)
  • Birefringence (nE-nO) 0.008 for visible light in directions orthogonal to the optic axis
  • Refractive index: 1.77 @500nm
  • Center Thickness (CT): +/-0.1
  • Parallelism: 3 arc minutes
  • Clear Aperture: 90% of diameter
  • Coating none

Contact us for manufacturing limit or custom specifications.

Sapphire Round Windows

Diameter(mm) Thickness(mm)
2.5 0.5
5.0 1.0
6.35 0.5
7.5 0.4
9.5 0.5
10.0 1.0
12.7 1.0
12.75 1.0
13.0 0.5
15.0 2.0
17.25 2.0
20.0 1.0
20.0 2.0
22.0 1.0
23.75 1.0
25.0 2.0
25.0 2.3
25.4 1.0
25.4 2.0
25.4 2.25
30.0 1.0
31.75 1.0
35.0 1.0
38.1 1.0
38.1 2.0
40.0 1.0
50.8 2.0
50.8 3.15
63.5 2.0
75.0 2.0

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