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  • Silicon (Si) Windows
  • Silicon (Si) Windows

Silicon (Si) Windows

  • Maximum diameter 300mm
  • Windows made for Czochralski or Float Zone Silicon
  • Transmission range 1.2-15μm
  • CZ silicon for MWIR (3-5μm) and FZ silicon for LWIR (8-12μm) applications
  • Coating options: DLC coating, AR coating
  • Low density for lightweight design and Low cost
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Materials Silicon crystals Diameter Range ~ 300mm
Aperture >90% Dimension Tolerance +0.0/-0.2mm
Thickness Tolerance +/-0.1mm Surface Quality 60/40 S/D
Parallelism 1 arc minute Chamfer 0.3-0.5mmx45degree
Coating AR/AR or DLC/AR


Material Properties:

Transmission Range 1.2 to 15 μm Refractive Index 3.4223 @ 5 μm (1) (2)
Reflection Loss 46.2% at 5 μm (2 surfaces) Absorption Coefficient 0.01 cm-1 at 3 μm
Reststrahlen Peak n/a dn/dT 160 x 10-6 /°C (3)
dn/dμ = 0 10.4 μm Density 2.33 g/cc
Melting Point 1420 °C Thermal Conductivity 163.3 W m-1 K-1 at 273 K
Thermal Expansion 2.6 x 10-6 / at 20°C Hardness Knoop 1150
Specific Heat Capacity 703 J Kg-1 K-1 Dielectric Constant 13 at 10 GHz
Youngs Modulus (E) 131 GPa (4) Shear Modulus (G) 79.9 GPa (4)
Bulk Modulus (K) 102 GPa Elastic Coefficients C11=167; C12=65; C44=80 (4)
Apparent Elastic Limit 124.1MPa (18000 psi) Poisson Ratio 0.266 (4)
Solubility Insoluble in Water Molecular Weight 28.09
Class/Structure Cubic diamond, Fd3m

Hangzhou Shalom EO offers Silicon (Si) Windows made from optical grade silicon ( Czochralski or Float Zone Silicon) for IR applications. The wide transmission of silicon spans from NIR to LWIR. Due to their low thermal conductivity, Si windows perform greatly in laser systems. Additionally, with its low density (2.329 g/cm3, half that of Ge or ZnSe), silicon is ideal for weight-sensitive The Knoop Hardness of silicon is 1150, in fact,  it is one of the hardest optical materials which are transparent to lights in the 1000-6000nm region.

The silicon crystal grown using the Czochralski method is particularly excellent for applications in MWIR (3-5μm) spectrum. After furnishing AR coating optimized for the wavelength range, the reflection of CZ silicon windows could be extremely low. However, CZ silicon has a strong absorption band at 9μm.  During the production process, Float Zone silicon is deliberately doped with Nitrogen and purified to reduce its carbon and oxygen composition, attenuating the absorption at 9μm, therefore FZ silicon windows could be used in the LWIR (8-12μm) range. 

In Shalom EO Silicon Windows are available in various custom dimensions, with a maximum diameter of 300mm. Coating options include DLC/AR coating and AR/AR coating.


1. Transmission curve of the Silicon windows (no coating)


2. Transmission curve of the Silicon windows with AR/AR coating at 3-5μm

3. Transmission of 0.5mm thickness FZ silicon windows without AR coating

4. Transmission of 0.5mm thickness FZ silicon windows with AR coating optimized at 8-12 micro