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Advanced Materials

In this industrial group, a vast variety of advanced optical materials and products including powders, ingots, optical lenses and windows, in different sizes and properties for visible and infrared applications are manufactured. The optical materials are produced in 3 categories:

  1. Single crystals
  2. Amorphous (glasses)
  3. Polycrystalline

 

Single crystals

Most important single crystal materials used in this industries are Germanium and Silicon. Single crystal Ge and Si produced by Czochralski method.

Germanium

Germanium is most widely used for lenses and windows in infrared systems operating in the 2-12 μm range. Due to wide transmission range and opaque in the visible, Ge is well suited for manufacturing of optical components for IR applications in lasers and optical systems. Germanium’s high refractive index makes Ge ideal for low power imaging systems because of minimum surface curvature. Chromatic aberration is small, often eliminating the need for correction. Germanium absorption increases with temperature. Pronounced transmission degradation starts at about 100°C and rapid degradation between 200°C and 300°C, resulting in possible catastrophic failure of the optic. Germanium components are used with AR coatings because of high surface reflectivity of substrate.

 

Ge crystal growth by Czochralski method

This industries offers SMTY blanks in diameters ranging from 7 mm to 300mm and thickness from 0.8mm to 40mm. Rectangular blank dimensions 200mmx200mm and thickness to 100mm. Resistivity 5-40 ohm-cm. Generated curved blanks from 15mm to 200mm in diameter are possible. Diameter tolerances are possible to 0.03mm with 0.1mm being the standard diameter tolerance. Prisms, tapers and other optical components according to customer specifications and drawings are possible.

IR Transmission vs. wavelength for Single crystalline Germanium

 

Also zone refined Ge ingot (poly crystalline) with 99.999% purity supplied by demand.

 

Ge single crystal properties

Transmission Range

1.8 to 23μm

Refractive Index

4.0026 at 11μm

Reflection Loss

53% at 11μm (Two surfaces)

Absorption Coefficient

<0.027 cm-1 @ 10.6μm

dn/dT

396 x 10-6 /°C

dn/dμ = 0

Almost constant

Density

5.33 g/cc

Melting Point

936 °C

Thermal Conductivity

58.61 W m-1 K-1 at 293K

Thermal Expansion

6.1 x 10-6/°C at 298K

Hardness

Knoop 780

Specific Heat Capacity

310 J Kg-1 K-1

Dielectric Constant

16.6 at 9.37 GHz at 300K

Youngs Modulus (E)

102.7 GPa

Shear Modulus  (G)

67 GPa

Bulk Modulus (K)

77.2 GPa

Elastic Coefficients

C11=129; C12=48.3; C44=67.1

Apparent Elastic Limit

89.6 MPa (13000 psi)

Poisson Ratio

0.28

Solubility

Insoluble in water

Molecular Weight

72.59

Class/Structure

Cubic Diamond, Fd3m

 
 
 
 
 

 

 

 

 

 

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 Thin Film Ge

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