BIOTAIN CRYSTAL > Substrate Materials > Optical windows > Product Information > Next :Zinc Selenide(ZnSe) window

Silicon(Si) window

Silicon(Si) window

Silicon(Si) optical window


 Single crystal of Silicon(Si)

Other Names

Silicon window substrate, Si window, Silicon IR window

Crystal structure

Face-centred Cubic

Applicable wave band

1.2μm ~ 8μm

Melting Point


Growth method

Czochralski(CZ) or Floating Zone(FZ)
Crystal properties

Orientation: <111>
Conductivity type: N-type
Resistivity: >15 ohm-cm or others

Refractive index

 3.4223 @5 μm

Absorption coefficient

 ≤0.01 /cm at 3μm

Knoop Hardness


Thermal conductivity

 273.3 W/mK

Coefficient of thermal expansion

 2.6×10-6/℃ at 20℃

Maximum size

 Diameter 260mm (Single crystal)

Material Standard Size Surface quality
Germanium(Ge) window φ10.0mm x 1.0mm
φ20mm x 2.0mm
φ25.4mm x 3.0mm
φ25.4mm x 5.0mm
φ50mm x 1.0mm
φ50.8mm x 3.0mm
12.7 x 12.7 x 3.0mm
25.4 x 25.4 x 3.0mm
Or others
Polishing:             Double side optical polished or Epi-polished
Roughness:          Ra<1.5nm or Ra 5~10nm, Ra<0.5nm, 
Size Tolerance:          +/-0.1mm
Thickness Tolerance: +/-0.1mm or +/-0.05mm
Parallelism:           1 minute, 30 seconds, 5 seconds or higher
Surface Finish:      60-40, 40-20, 20-10 (scratch-dig)
Surface Figure:      1/2λ, 1/4λ or higher
Chamfer:                0.25mm × 45°
Coating:                 Upon requirements

Silicon windows and Germanium windows are the most commonly used Infrared(IR) windows. The best working wavelength of single crystal Silicon windows is 3-5um, and the best working wavelength of single crystal Germanium windows is 2-14um. It is one of the best substrate materials for filters.

Silicon(Si) window has good light transmission performance in the 1.2-7um wave band. Single crystal Silicon has good thermal conductivity and stability, low thermal expansion coefficient, relatively low density (half of Germanium window or Zinc Selenide window), with low cost. It is currently the first choice of material for CO2 laser mirrors. Commonly used in the production of laser mirrors and more sensitive to volume and weight.

Silicon window can be divided into Transmissive Grade and Mirror Grade. The Transmission-grade Silicon (OCZ-Si) is growth by Czochralski and widely used in the mid-Infrared (1-6um) band. The Silicon window growth by Floating zone(FZ-Si) can be used in a wider band (1--14um), the high purity Silicon window (HPFZ-Si) can even be used in the far Infrared band (30-300 μm).

We can customize different size and thickness of Silicon(Si) optical window upon requirements, such as Silicon(Si) round wafer, Square substrate and Cylinder, or Punch holes and other shapes.


Contact Us

  • Tel: (+86) 1506 0796 451
  • Fax: (+86) 0597 2212602
  • Email:
  • Work Time ( GMT +8 ):
  •    9 AM ~ 6 PM, Monday to Friday
  • Main office: A7, No. 501, Denggaoxi Road, Xipi street, Xinluo District, Longyan, Fujian, China