Sapphire – Al2O3

lenses, windows, mirrors, filters and prisms

Sapphire (Al2O3) is a superior optical material which is used for its excellent optical, chemical and physical properties for use in the UV, Visible and Infra-red regions. Sapphire crystal is extremely hard and scratch resistant. It is the hardest of the oxide crystals, being the next strongest material to diamond, and is able to be cut thinner than alternative crystals due to its structural durability.

 Standard grade Sapphire material is grown by Verneuil and Czochralski methods, whereas higher quality Sapphire is manufactured by the Kyropulus growth method.

Sapphire crystal has a refractive index of 1.75 and is grown to a random orientation. It is slightly birefringent so general purpose infra red windows are usually cut in a random way, however, for specific applications where birefringence is an issue, an orientation is selected. Just a few of the Orientations available are: C-Plane, A-Plane and R-Plane.

Sapphire optical material has excellent thermal conductivity at low temperatures allowing single crystal Sapphire to be used in many diverse fields requiring thermal conductivity and heat radiation. It can operate up to 2030C. Sapphire has a dielectric constant making it resistant to common acids and alkaline up to 1000C. It is also unaffected by weathering and hydration. Synthetic Optical Sapphire has no colouration and with a selection of grades of Sapphire available, transmission ranges from 170nm to 6 microns.

All of these properties encourage Sapphires wide use in hostile environments where optical transmission is in the range from vacuum ultraviolet (VUV) to the near Infra-red (N-IR). It is used in many applications:

Military – sapphire windows and lenses can protect sensors, cameras and lasers from the extreme conditions in air, water and on the ground

Medical – There are numerous uses in the medical industry ranging from skin contact windows, hair removal lasers, pharmaceutical monitoring and endoscopy

Pressure Situations – the extreme durabililty of sapphire allows it to withstand high pressure making it ideal for deep ocean and high vacuum chamber cameras or lasers.

Global Optics (UK) Ltd. can supply custom manufactured parts to your specification with both exceptional quality and very competitive prices. Sapphire windows, lenses,  prisms, mirrors and blanks can all be manufactured with various dimensions, tolerances and orientations. Global Optics is also able to supply a range of C-cut and Z-cut Sapphire for UV applications.

Transmission Range 0.17 – 6.5 µ
Crystal Structure
Cleavage Plane None
Colour colourless
Density 3.98
Melting Point (°) 2030
Reflection Loss 12.0% (4µ) for 2 surfaces
Solubility index insoluble
Hardness (Knoop) 1370
Thermal Conductivity (cal/cm sec°C) 6.0×10-2 (Parellel to C axis)
5.5×10-2 (Vertical to C axis)
Thermal Expansion coefficient (/°C) 6.7×10-6 (Parellel to C axis)
5.0×10-6 (Vertical to C axis)
Sapphire (Al203) windows and Sapphire (Al203) lenses

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