Material - Silicon (Si)
Silicon is used as an optical window primarily in the 3 to 5 micron band and as a substrate for production of optical filters.
It is frequently used for laser mirrors because of its high thermal conductivity and low density. Silicon is also useful as a transmitter in the 20 micron range. Large blocks with polished faces are also employed as targets in neutron physics experiments.Silicon is grown by Czochralski pulling techniques (CZ) and contains some oxygen which causes an absorption band at 9 microns. To avoid this, material can be prepared by a Float-Zone (FZ) process. Optical silicon is generally lightly doped ( 5 to 40 ohm cm) for best transmission above 10 microns. Silicon has a further pass band 30 to 100 microns which is effective only in very high resistivity uncompensated material.
BASE PROPERTIES
|
PARAMETER |
|
VALUE |
|
|
|
|
|
|
| OPTICAL |
|
| |
Transmission Range |
|
1.2 to 15 microns |
|
| |
Refractive Index |
|
3.4223 at 5 microns |
|
| |
Reflection Loss |
|
51.0% at 5 µm (2 surfaces) |
|
| |
dn/dT |
|
160 x 10-6/K |
|
| |
dN/dµ = 0 |
|
10.4µm |
|
| |
Index of Absorption |
|
1 x 10-3 cm-1 at 3 microns |
|
| PHYSICAL |
|
| |
Density |
|
2.33 g/cm3 |
|
| |
Melting Point |
|
1420° C |
|
| |
Thermal Conductivity |
|
163.3 Wm-1K-1 at 273K |
|
| |
Thermal Expansion |
|
4.15 x 10-6/°C |
|
| |
Hardness |
|
Knoop 1150 |
|
| |
Specific Heat Capacity |
|
703 J/(kg K) |
|
| |
Dielectric Constant |
|
13 at 10GHz |
|
| |
Young's Modulus (E) |
|
131 GPa |
|
| |
Shear Modulus (G) |
|
79.9 GPa |
|
| |
Bulk Modulus (K) |
|
102 GPa |
|
| |
Elastic Coefficients |
|
C11=167 MPa, C12=65
MPa,
C44=80 MPa |
|
| |
Poisson Ratio |
|
0.266 |
|
| CHEMICAL |
|
| |
Solubility |
|
Insoluble in water |
|
| |
Molecular Weight |
|
28.09 |
|
| |
Class/Structure |
|
Cubic diamond, Fd3m |
|
REFRACTIVE INDEX
| |
Wavelength, µm |
1.40 |
1.50 |
1.66 |
1.82 |
2.05 |
2.50 |
3.50-5.00 |
6.00-25.00 |
|
| |
Refractive Index |
3.49 |
3.48 |
3.47 |
3.46 |
3.45 |
3.44 |
3.43 |
3.42 |
|
|
