Materials>>Silicon window

Silicon windows, Silicon lenses

Alkor Technologies produces wide range of Silicon optical components according to customer's specification:

The largest dimensions of Silicon optics - 150mm diameter.

Silicon is used as a high reflectivity mirror for lasers. Silicon is also used for windows and lenses in the 1mkm to 7mkm range. The refractive index is near 3.4 throughout the range. Silicon high thermal conductivity and low weight are attractive features in IR/FTIR applications .

Si transmission

Float-zone Silicon transmittance. Sample thickness 10mm.

Different types of Silicon are available:

  • Czochralski standard low-cost n-type (resistivity >10 Ohm*cm) or p-type (>20 Ohm*cm)
  • high resistivity Float-Zone Silicon with resistivity >1000 Ohm*cm.

Due to the strong absorbtion at 9mkm, Silicon is not suitable for use with CO2 lasers as a transmitting optic but is widely used for CO2 mirrors. The density of Silicon is only half that of Germanium and Zinc Selenide.

Silicon properties
Chemical Formula Si
Molecular Weight 28.09
Crystal Class Cubic
Lattice Constant, Å 5.43
Density, g/cm3 at 293 K 2.329
Dielectric Constant for 9.37 x 109 Hz 13
Melting Point, K 1690
Thermal Conductivity, W/(m K)
at 125 K
at 313 K
at 400 K

598.6
163
105.1
Thermal Expansion, 1/K
at 75 K
at 293 K
at 1400 K

-0.5 x 10-6
2.6 x 10-6
4.6 x 10-6
Specific Heat, cal/(g K)
at 298 K
at 1800 K

0.18
0.253
Debye Temperature, K 640
Bandgap, eV 1.1
Solubility in water None
Knoop Hardness, kg/mm2 1100
Mohs Hardness 7
Young's Modulus, GPa 130.91
Shear Modulus, GPa 79.92
Bulk Modulus, GPa 101.97
Poisson's Ratio 0.28
Silicon index of refraction
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