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  • Sapphire Windows
  • Sapphire Windows

Sapphire Windows

  • Exceptional mechanical strength and chemical resistance
  • High thermal durabilities excellent for harsh environments
  • Maximum diameter 300mm
  • Broad wavelength range from 150-5500nm
  • Blank substrates, AR-coated pieces, and precision windows are available
  • Check out our Sapphire Window Stock List here
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Specifications:

Materials Sapphire crystals Diameter Range Max. 300mm
Aperture >90% Dimension Tolerance +0.0/-0.2mm
Thickness Tolerance +/-0.1mm Surface Quality Optional: 60/40, 40/20 or 20/10 S/D
Parallelism 30 arc sec Chamfer 0.3-0.5mmx45°
Coating No coating, or single layer MgF2 and other custom coating options
 

Basic Properties:

Transmission Range 0.17 to 5.5 μm Refractive Index No 1.75449; Ne 1.74663 at 1.06 μm
Reflection Loss 14% at 1.06 μm Absorption Coefficient 0.3 x 10-3 cm-1 at 2.4 μm
Reststrahlen Peak 13.5 μm dn/dT 13.1 x 10-6 at 0.546 μm
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

Infrared Sapphire (Al2O3) Windows, featuring broad optical transmission from 150-5500nm spanning from UV to MWIR spectrum, and robust mechanical/thermal properties, are excellent for applications involving harsh and variant environments or requiring a broad transparent wavelength range (e.g. windows of sensors and detectors, IR applications, etc.). 

The material's most distinguishing attribute is its unequaled mechanical strength, being the second hardest material after diamond, single sapphire crystals have a Knoop Hardness of 1800-2200, making the windows made from single crystals sapphire resistant in extreme to chemical corrosion and abrasions. Sapphire windows might be produced into thin optics without fracturing because of the tight internal covalent bonding of single-crystal sapphire while demonstrating good thermal stabilities due to its high thermal conduction.

Shalom EO offers various forms of Infrared Optical Sapphire Windows including flat windows with parallel faces, circular/rectangular windows, wedge windows, and other custom specifications. Large aperture sapphire windows with diameters up to 300mm are available, and surface qualities of 60/40, 40/20, and 20/10 Scratch/Dig are optional according to the precision requirements of your interest. Our blank sapphire substrates feature high transmission in the wavelength range between 2.5-4.5µm with an average transmission rate above 85%. Single-film MgF2 coatings and other AR coatings could be furnished to increase transmission. Precision sapphire windows requisite for laser systems are also procurable upon request. In convention, our sapphire windows are z-cut in order to prevent birefringence. Besides, we also provide a large selection of Stocked Sapphire Windows.


Application Notes: C-cut and Random-Cut Sapphire Windows:

The orientation of a crystal is a vector describing a random line connecting two nodes on the lattice. Due to the anisotropic nature of crystals, the distribution and the arrangement manner of the atoms change along different directions or upon different lattice planes. The result of this is that the properties and behaviors, even of the same crystals, but with different orientations will differ to a significant extent. This is the reason of choosing the proper orientations and cutting planes of crystals is critical when using crystals to produce various components and elements. 

The Sapphire crystals utilized to produce sapphire windows of different functions will be grown and cut/sliced with an engineered orientation, and the orientation is often determined because it will optimize the crystal’s performance to achieve the intentions of interest.

The lattices within the sapphire are arranged in a hexagonal structure. When a sapphire element is produced, the direction of its inner architecture affects the functionalities of the element.


sapphire structuresapphire window orientation   

Figure 4.The Lattice Structure of Sapphire and Common Sapphire Crystal Orientations


C-Cut Sapphire Windows has an orientation index of (0001). The sapphire is cut in a direction perpendicular to the c-axis. The c-axis is the optical axis of sapphire. light projected along the direction of the optical axis will not encounter birefringence. In practice, the light will be incident with a perpendicular angle to the apertures of the sapphire windows, which means the light will travel inside the sapphire windows parallel to the optical axis, eliminating the birefringence effect. C-cut sapphire windows are often chosen for critical optical missions (e.g. laser windows). C-cut sapphire is sometimes called zero-degree sapphire, or z-cut sapphire.

There are also Random-cut Sapphire Windows. Random-cut implies the element is cut or sliced with no specific regard to directions, it might contain any orientations. This orientation is common because of lower costs and is acceptable if there are no stringent requirements about optical or mechanical qualities. However, as mentioned above, because the behavior of sapphire varies depending on orientations, random orientation might be subject to spontaneous variations of strength and other properties in the final product.

Before the cutting or slicing procedure, sometimes the manufacturer would grow the bulk sapphire crystal of a specific orientation. For example, the bulk sapphire designated to produce a c-cut sapphire window will be grown with an orientation that maximizes the utilization efficiencies of the c-planes.

Curves:
Transmission curve of the Sapphire windows (no coating)