to the WORLD of CRYSTALS
Single Crystals Germanium (Ge) and Silicon (Si)
Print this frame

Silicon Germanium
Germanium (Ge) is most widely used for lenses and windows in IR systems operating in the 2 - 12 µm range. The enviroment does not make any problems because Germanium is inert, mechanically rugged, and fairly hard. It is an excellent choice for multi-spectral systems and for applications where EMI shielding is necessary. Germanium can be electrically heated for anti-fogging or anti-icing applications. We do not manufacture Germanium, but hold stock of Czochralsky grown material of various diameters. It can be used as a polycrystalline or as a single crystal. The purity should correspond to an electrical resistivity of at least 20 to 30 Ohm/cm, either p- or n-type to avoid absorption bands. The high retractive index makes AR-coating essential.
   Silicon (Si) is commonly used as a substrate material for infrared reflectors and windows in the 1.5 - 8 µm region. The strong absorption band at 9 µm makes it unsuitable for CO2-laser transmission applications, but it is frequently used for laser mirrors because of its high thermal conductivity and low density. Silicon is also a usefull transmitter in the 20 µm range.
Main properties of Ge:

Crystal symmetry m3m
Density 5.3267 g/cm3
Optical spectral range 1.5 - 22 µm
Elastic constants cij (1011 dyn/cm2 or 1010 Pa):

13 4.9 4.9 0 0 0
4.9 13 4.9 0 0 0
4.9 4.9 13 0 0 0
0 0 0 6.7 0 0
0 0 0 0 6.7 0
0 0 0 0 0 6.7
Photoelastic constants pij:

-0.154 -0.126 -0.126 0 0 0
-0.126 -0.154 -0.126 0 0 0
-0.126 -0.126 -0.154 0 0 0
0 0 0 -0.073 0 0
0 0 0 0 -0.073 0
0 0 0 0 0 -0.073
Sound velocity:
direction polarization v (105 cm/s)
[100] [100] 4.99
[110] [110] 5.41
[111] [111] 5.5
[100] S 3.55
[110] [1-10] 2.75
[111] S 3.04
Acousto-optic figure of merit:
sound dir. sound pol. light dir. light pol. M (10-18 s3/g)
[111] [111] - [111] 840
[100] [010] - arb. 290
Refraction indices:
l (µm) nx ny nz
1.8 4.143 4.143 4.143
1.9 4.129 4.129 4.129
2 4.116 4.116 4.116
2.1 4.104 4.104 4.104
2.2 4.092 4.092 4.092
2.3 4.085 4.085 4.085
2.4 4.078 4.078 4.078
2.5 4.072 4.072 4.072
2.6 4.068 4.068 4.068
2.998 4.0453 4.0453 4.0453
3.303 4.0370 4.0370 4.0370
3.419 4.0336 4.0336 4.0336
4.258 4.0217 4.0217 4.0217
4.866 4.0170 4.0170 4.0170
6.238 4.0092 4.0092 4.0092
8.660 4.0036 4.0036 4.0036
9.720 4.0026 4.0026 4.0026
11.04 4.0020 4.0020 4.0020
12.12 4.0018 4.0018 4.0018
13.02 4.0016 4.0016 4.0016
14.21 4.0015 4.0015 4.0015
15.08 4.0014 4.0014 4.0014
16.00 4.0012 4.0012 4.0012

NOTE: It should be taken into account that nx=ny=nz=n for optically isotropic material and nx=ny=no and nz=ne for uniaxial crystal.
NOTE: In those cases when different researchers give distinct values of constants, avaraged data are presented in Tables.

The deliveries from ground to finished Si- or Ge-blanks as well as processed uncoated or AR-coated optical elements are possible.

I N Q U I R Y    F O R M :

Material:
Quantity of elements:
Application:
polished sites:

BLOCK    or  BLOCK
  a-b b-c a-c
or d  
Orientation:
(if applicated)
Dimensions/Tolerances:
 For example:
10.0 +/- 0.1
AR-coating:
a = mm;
c = mm		 b = mm or
dia. = mm;
This field is for additional information such as application,
comments, add. requirements etc.
Name:
Tel-No: 
Fax:
E-Mail:
Your company name and address:
Cancel