Infrared Optical Material - Si
Silicon (Si) is grown by Czochralski pulling techniques (CZ) and contains some that causes an absorption band at 9 microns. To avoid this, material can be prepared by Float-Zone (FZ) process.Optical silicon is generally lightly doped (5-40 ohm cm) for best transmission above 10 microns, and doping is usaully boron (p-type) and phosphorus (n-type). After doping silicon has a further pass band: 30 to 100 microns which is effective only in very high resistivity uncompensated material.
CZ Silicon is commonly used as substrate material for infrared reflectors and windows in the 1.5-8 micron region. The strong absorption band at 9 microns makes it unsuitable for Co2 laser transmission applications, but it is frequently used for laser mirrors because of its high thermal conductivity and low density. Application as window, lens in the 1.5-8 µm region; Mirror for Co2 laser and spectrometer applications.
Si Optical grade
- CZ, P type doped with Boron, <111> or <100>, Resistivity 5-40 ohm cm
- FZ, N type doped with phosphorus, <111>, Resistivity > 50, preferably > 500 ohm cm, the absorption at 9 microns is absent.
| Optical Properties | |||
|---|---|---|---|
| Transmission Range | 1.2~8µm | ||
| Reflection Loss, for two surfaces at 5µm | 46.2% | ||
| Reflection Index | See below | ||
| Wavelength (µm) | Refractive Index (n) | Wavelength (µm) | Refractive Index(n) |
1.357 |
/ |
5.500 |
3.4213 |
1.3951 |
3.4975 |
6.000 |
3.4202 |
1.6606 |
3.4929 |
6.500 |
3.4195 |
1.8131 |
3.4608 |
7.000 |
3.4189 |
2.1526 |
3.4476 |
7.500 |
3.4186 |
2.3254 |
3.443 |
8.000 |
3.4184 |
3.000 |
3.432 |
8.500 |
3.4182 |
3.500 |
3.4284 |
10.00 |
3.4179 |
4.000 |
3.4257 |
10.50 |
3.4178 |
4.500 |
3.4236 |
11.04 |
3.4176 |
5.000 |
3.4223 |
||
| Physical properties | |
|---|---|
| Density | 2.33g/cm3 |
| Hardness, Mohs | 7 |
| Dielectric Constant for 9.37 x 109Hz | 13 |
| Melting point, °C | 1414 |
| Thermal Conductivity, W/m·K at 313 K | 163 |
| Thermal Expansion, 1/K at 293 K | 2.6x10-6 |
| Specific Heat Capacity, J(kg·°C) | 712.8 |
| Bandgap, eV | 1.1 |
| Knoop Hardness, kg/mm2 | 1100 |
| Young's Modulus, Gpa | 130.91 |
| Shear Modulus, Gpa | 79.92 |
| Bulk Modulus, Gpa | 101.97 |
| Debye Temperature, K | 640 |
| Poisson's Ratio | 0.28 |
| Chemical properties | |
| Solubility in water | None |
| Molecular Weight | 28.09 |
