Sapphire – Al203

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. Sapphire is able to be cut thinner than alternative crystals due to its structural durability.

Sapphire is grown using a variety of methods. 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. Sapphire 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 Sapphire’s wide use in hostile environments where optical transmission is in the range from vacuum ultraviolet (VUV) to the near Infra-red (N-IR). Sapphire can be used in many areas of life, such as Military; sensors, cameras and lasers can be protected by Sapphire windows or lenses from the extreme conditions our military experience in air, water and on the ground; Medical; There are various uses in the medical industry ranging from skin contact windows, hair removal lasers, pharmaceutical monitoring and endoscopy; and Pressure Situations; Deep Oceans and high vacuum chamber cameras or lasers can be protected by Sapphire windows due to its extreme durability making it able to withstand high pressure.

Global Optics (UK) Ltd. can supply custom manufactured parts to your specification with both exceptional quality and very competitive prices. Sapphire windows, Sapphire lenses, Sapphire prisms, Sapphire mirrors and Sapphire 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)