Infrared Optical Material - Sapphire
Sapphire initially refers to gem varieties of the mineral corundum, an aluminium oxide (Al2O3), when it is a color other than red. Nowadays, sapphire can be found naturally or manufactured in large crystal boules. Sapphire is highly transparent at wavelengths of 170 nm to 5.3 μm (ultraviolet to infrared), as well as being five times stronger than glass. This leads to use of synthetic sapphire windows in high pressure chambers for spectroscopy. The hardest of the oxide crystals, sapphire retains its high strength at high temperatures and has good thermal properties. It is well known for chemically resistant to common acids and alkali at temperatures up to 1000 °C as well as to HF below 300 °C.
Maximum available size for windows, lenses and blanks: 100 mm Dia x 10 mm Thk and 100 mm Square x 10 mm Thk.
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| BASE PROPERTIES | |
|---|---|
| PARAMETER | VALUE |
| OPTICAL | |
| Transmission Range | 0.17 to 5.5 microns |
| Refractive Index | 1.75449 (o) 1.74663 (e) at 1.06 microns |
| Reflection Loss | 14% at 1.06 microns (2 surfaces) |
| Absorption Coefficient | 0.3 x 10-3e cm-1 at 2.4μm |
| Restrahlen Peak | 13.5μm |
| dN/dT | 13.7 x 10-6e at 5.4μm |
| dN/dμ = 0 | 1.5μm |
| PHYSICAL | |
| Density | 3.97 g/cm3 |
| Melting Point | 2040°C |
| Thermal Conductivity | 27.21 W/(m*K) at 300K |
| Thermal Expansion | 5.6 (paral) & 5.0 (perp) x 10-6e/K * |
| Hardness | Knoop 2000 with 2000g indenter |
| Specific Heat Capacity | 419 J/(kg K) |
| Dielectric Constant | 11.5 (paral) 9.4 (perp) at 1MHz |
| Young's 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 | 275 MPa (40,000 psi) |
| Poisson Ratio | 0.25 |
| CHEMICAL | |
| Solubility | 98x10-6 g/100g water |
| Molecular Weight | 101.96 |
| Class/Structure | Trigonal (hex), R3c |
| REFRACTIVE INDEX | ||||||
|---|---|---|---|---|---|---|
| Wavelength, μm | 0.308 | 0.325 | 0.337 | 0.351 | 0.355 | 0.442 |
| Refractive Index (ne) | 1.811 | 1.805 | 1.801 | 1.797 | 1.796 | 1.780 |
| Refractive Index (no) | 1.802 | 1.796 | 1.792 | 1.788 | 1.787 | 1.772 |
| Wavelength, μm | 0.458 | 0.488 | 0.55 | 0.532 | 0.590 | 0.633 |
| Refractive Index (ne) | 1.778 | 1.775 | 1.773 | 1.772 | 1.768 | 1.766 |
| Refractive Index (no) | 1.770 | 1.767 | 1.765 | 1.764 | 1.760 | 1.758 |
| Wavelength, μm | 0.670 | 0.694 | 0.775 | 0.780 | 0.800 | 0.820 |
| Refractive Index (ne) | 1.764 | 1.763 | 1.761 | 1.761 | 1.760 | 1.760 |
| Refractive Index (no) | 1.756 | 1.755 | 1.753 | 1.753 | 1.752 | 1.7528 |
| Wavelength, μm | 0.980 | 1.064 | 1.320 | 1.550 | 2.010 | 2.249 |
| Refractive Index (ne) | 1.756 | 1.754 | 1.750 | 1.746 | 1.737 | 1.732 |
| Refractive Index (no) | 1.748 | 1.747 | 1.742 | 1.738 | 1.729 | 1.724 |
| Wavelength, μm | 2.703 | 2.942 | 3.333 | 3.704 | 4.000 | 4.348 |
| Refractive Index (ne) | 1.719 | 1.712 | 1.701 | 1.687 | 1.674 | 1.658 |
| Refractive Index (no) | 1.711 | 1.704 | 1.693 | 1.699 | 1.666 | 1.65 |
| Wavelength, μm | 4.762 | 5.000 | 5.263 | |||
| Refractive Index (ne) | 1.636 | 1.623 | 1.607 | |||
| Refractive Index (no) | 1.628 | 1.615 | 1.599 | |||