Germanium Ge
DownloadGermanium is a high index material that is used to manufacture Attenuated Total Reflection (ATR) prisms for spectroscopy. Its refractive index is such that Germanium makes an effective natural 50% beamsplitter without the need for coatings. Germanium is also used extensively as a substrate for production of optical filters. Germanium covers the whole of the 8-14 micron thermal band and is used in lens systems for thermal imaging. Germanium can be AR coated with Diamond producing an extremely tough front optic.
| µm | No |
|---|---|
| 2.058 | 4.102 |
| 2.153 | 4.0919 |
| 2.313 | 4.0786 |
| 2.437 | 4.0708 |
| 2.577 | 4.0609 |
| 2.714 | 4.0562 |
| µm | No |
|---|---|
| 2.998 | 4.0452 |
| 3.303 | 4.0369 |
| 4.258 | 4.0216 |
| 4.866 | 4.017 |
| 6.238 | 4.0094 |
| 8.660 | 4.0043 |
| µm | No |
|---|---|
| 9.720 | 4.0034 |
| 11.04 | 4.0026 |
| 12.00 | 4.0023 |
| 13.02 | 4.0021 |
Germanium is grown using the Czochralski technique by a small number of manufacturers in Belgium, USA, China and Russia. The refractive index of Germanium changes rapidly with temperature and the material becomes opaque at all wavelengths a little above 350K as the band gap floods with thermal electrons.
REFERENCES:
(1) Handbook Optical Constants, ed Palik, V1, ISBN 0-12-544420-6
(2) Li, Refractive Index of Germanium etc, J.Phys Chem, V9, p561, 1980
(3) Pearson & Brattain, Proc. Inst. Radio Eng. V43, p1794, 1955
(4) Fine, J.App.Phys, V24, p338, 1953
(5) Wortman & Evans, V36, (1), P153 (1965)
(6) Hawkins, Sherwood, Djotni: Mid IR Filters for astronomical and remote sensing instrumentation. Invited Paper SPIE Conference Glasgow 2008
(7) Manufactures Published Data