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Sapphire windows

  • Extreme surface hardness and chemical resistance
  • Maximum diameter 300mm
  • Broad wavelength range from UV to MWIR
  • AR coating available
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Materials Sapphire crystals Diameter Range ~ 250mm
Aperture >90% Dimension Tolerance +0.0/-0.2mm
Thickness Tolerance +/-0.1mm Surface Quality 60/40 S/D
Parallelism 1 arc minute Chamfer 0.3-0.5mmx45degree
Coating No coating or single layer MgF2

Basic Properties:

Transmission Range 0.17 to 5.5 μm Refractive Index No 1.75449; Ne 1.74663 at 1.06 μm (1)
Reflection Loss 14% at 1.06 μm Absorption Coefficient 0.3 x 10-3 cm-1 at 2.4 μm (2)
Reststrahlen Peak 13.5 μm dn/dT 13.1 x 10-6 at 0.546 μm (3)
dn/dμ = 0 1.5 μm Density 3.97 g/cc
Melting Point 2040°C Thermal Conductivity 27.21 W m-1 K-1 at 300K
Hardness Knoop 2000 with 2000g indenter Specific Heat Capacity 763 J Kg-1 K-1 at 293K (4)
Dielectric Constant 11.5 (para) 9.4 (perp)at 1MHz Youngs Modulus (E) 335 GPa
Shear Modulus (G) 148.1 GPa Bulk Modulus (K) 240 GPa
Elastic Coefficients C11=496 C12=164 C13=115 C33=498 C44=148 Apparent Elastic Limit 300 MPa (45,000 psi)
Poisson Ratio 0.25 Solubility 98 x 10-6 g/100g water
Molecular Weight 101.96 Class/Structure Trigonal (hex), R3c

Sapphire or aluminum oxide (Al2O3) is single crystal and is useful in a transmission range from 0.2 - 5.5μm, sapphire is suitable for MWIR 3-5μm thermal imaging applications. Sapphire Windows are made from single crystal sapphire, they are ideal for demanding applications for their extreme surface hardness, high thermal conductivity, high dielectric constant and resistance to common chemical acids and alkalis. Sapphire is the second hardest crystal next to diamonds and, because of their structural strength, sapphire windows can be made much thinner than other common dielectric windows with improved transmittance.

Transmission curve of the Sapphire windows (no coating)