Optical Windows

Optical Windows

Optical grade Silicon is normally specified with a resistivity of 5 to 40 ohm-cm for best transmission about 10 μm. Silicon windows has a further pass band 30 to 100 microns which is effective only in very high resistivity material. 

Sil’tronix is growing is Silicon by Czochralski pulling techniques (CZ). This pulling technic produces a Silicon which contains some oxygen, causing an absorption band at 5.8, 9.1 and 19.4 microns. To avoid this, Float Zone (FZ) material can be supplied which does not have this absorption.

Our monocrystal Silicon optical windows is frequently used for laser mirrors thanks to its high thermal conductivity and low density. Our products are also useful as a transmitter in the 20 micron range and also are largely employed as targets in neutron physics experiments. 

Typical applications:

  • XRD (Xray diffraction analysis)
  • SEM (scanning electron microscope)
  • AFM (atomic force  microscope)
  • FTIR infrared
  • Fluorescence spectroscopy analysis 
  • Synchrotron sample carrier radiation experiment 
  • Molecular beam epitaxial growth substrate

Very high resistivity material can be supplied on special order, particularly for Tera Hertz applications.

Standard Optical windows double side polished

Sil'Tronix - Silicon windows sitronix.jpg

Diameter Thickness
mm Inches
10 0,5 to 5 mm
25
25,4 1
30
50
50.8 2
76.2 3
101.6 4

General Tolerances

  • Diameter: +/- 0.1 mm
  • Thickness: +/- 0.1 mm
  • Parallelism: 30 µm
  • Planarity: 1.5 µm
  • Crystal orientation: +/- 1.5 °

As Sil’Tronix is a silicon product custom manufacturer, we would be pleased to quote you to your exact specifications (diameter, thickness, tolerance or even crystal orientation)

More information about our silicon optical windows

Sil’Tronix Silicon is an ideal material for many of mid-wave IR (MWIR) applications because of its optical properties, and its value is enhanced even more by its environmental durability, light weight, thermal stability, and natural abundance.

Birefringence can degrade IR imaging performance, and silicon has an advantage here, too. Crystals with cubic crystalline structure exhibit no birefringence while non-cubic crystals will exhibit birefringence. Silicon is cubic in nature and will not exhibit birefringence.

Durability is an often overlooked aspect when specifying MWIR applications. Most IR transmissive materials are soft, brittle, and water soluble, which can be limiting depending on the application. Although transmission is the most important material property, MWIR applications can take advantage of silicon’s high environmental durability. 

Weight sensitivity is also of particular concern in many IR imaging applications, especially if the device will be worn by the end user. The most popular IR materials, germanium and zinc selenide, are dense and add significant weight to the system. Silicon has a lower density (2.33g/cm3) making it ideal for weight-sensitive applications.

Thermal stability is another key consideration in MWIR applications. The change in index with respect to temperature of most IR materials is orders of magnitude higher than those of visible glasses. Silicon is thermally stable, characterized by a low dn/dT, particularly in respect to germanium.

Commercial applications of MWIR technology tend to be more cost-sensitive than defense applications. Due to its natural abundance in comparison to other IR materials, silicon is significantly cheaper, particularly as size increases. For example, a comparably-sized germanium window can be 2-3X more expensive.


 

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