Sapphire (Al₂O₃)
Sapphire, or single-crystal aluminum oxide (Al₂O₃), is a highly valued material in optics due to its exceptional physical and optical properties. It is renowned for its wide transmission range, spanning from the ultraviolet (UV) to the infrared (IR) spectrum. Sapphire’s high refractive index, extreme hardness, and excellent thermal and chemical resistance make it ideal for demanding applications, including high-pressure windows, lenses, and substrates in aerospace, defense, and industrial systems. Its robustness allows it to withstand harsh environmental conditions, making sapphire a preferred choice for durable and reliable optical components in a variety of advanced technological applications.
Optical Properties
Refractive Index: No = 1.75449, Ne = 1.74663
Thermal Co-efficient of Refractive Index: 13.1 x 10-6
Transmission Range: 0.2 – 5.2 µm
Thermal Properties
Thermal Linear Expansion: 27.2 W m⁻¹ K⁻¹ at 300 K
Thermal Conductivity: 763 J Kg⁻¹ K⁻¹
Specific Heat Capacity: 339 J Kg⁻¹ K⁻¹
Melting Point: 2040 °C
Mechanical Properties
Density: 3.97 g/cc
Knoop Hardness: 1800 & 2200
Young Modulus: 335 GPa
Shear Modulus: 148.1 GPa
Bulk Modulus: 240 GPa
Poisson Ratio: 0.25
| Wavelength (µm) | no | ne |
| 0.193 | 1.9288 | 1.9174 |
| 0.213 | 1.8890 | 1.8784 |
| 0.222 | 1.8754 | 1.8650 |
| 0.226 | 1.8702 | 1.8599 |
| 0.244 | 1.8506 | 1.8407 |
| 0.248 | 1.8470 | 1.8372 |
| 0.257 | 1.8393 | 1.8297 |
| 0.266 | 1.8330 | 1.8236 |
| 0.280 | 1.8244 | 1.8151 |
| 0.308 | 1.8110 | 1.8020 |
| 0.325 | 1.8047 | 1.7958 |
| 0.337 | 1.8001 | 1.7921 |
| 0.351 | 1.7969 | 1.7882 |
| 0.355 | 1.7960 | 1.7883 |
| 0.442 | 1.7804 | 1.7721 |
| 0.458 | 1.7784 | 1.7702 |
| 0.488 | 1.7753 | 1.7671 |
| 0.515 | 1.7730 | 1.7649 |
| 0.532 | 1.7717 | 1.7636 |
| 0.590 | 1.7680 | 1.7600 |
| 0.633 | 1.7659 | 1.7579 |
| 0.670 | 1.7643 | 1.7563 |
| 0.694 | 1.7634 | 1.7554 |
| 0.755 | 1.7614 | 1.7535 |
| 0.780 | 1.7607 | 1.7527 |
| 0.800 | 1.7601 | 1.7522 |
| 0.820 | 1.7596 | 1.7517 |
| 0.980 | 1.7561 | 1.7482 |
| 1.064 | 1.7545 | 1.7466 |
| 1.320 | 1.7501 | 1.7423 |
| 1.550 | 1.7462 | 1.7384 |
| 2.010 | 1.7375 | 1.7297 |
| 2.249 | 1.7323 | 1.7243 |
| 2.703 | 1.7190 | 1.7110 |
| 2.941 | 1.7120 | 1.7110 |
| 3.333 | 1.7010 | 1.6930 |
| 3.704 | 1.6870 | 1.6790 |
| 4.000 | 1.6740 | 1.6660 |
| 4.348 | 1.6580 | 1.6500 |
| 4.762 | 1.6360 | 1.6280 |
| 5.000 | 1.6230 | 1.6150 |
| 5.263 | 1.6070 | 1.5990 |
