What Are Performance Parameters of Germanium Crystal?

Table of Contents

Introduction

Single Germanium (Ge) crystal is a chemically inert material with a transmission spectral range of 2-12µm.

It is a very commonly used infrared optical material with high hardness, good thermal conductivity and insoluble in water. It is widely used in infrared imaging system and infrared spectrometer system.

Transmittance Curve of Germanium Crystal

The curves of single Germanium crystal‘s ability to transmit light of different wavelengths are shown in the following figure, which shows the relative intensity of light transmitted at different wavelengths.

Germanium Crystal

Optical Parameter Table

Transmittance wavelength range2000nm-12000nm
Absorption coefficient(1/cm)1.3*10-3 @3800nm
3*10-2 @10600nm
Thermo-optical coeffecient, dn/dT(1/k)4.08*10-4 @10600nm

Variation of Refractive Index with Wavelength

At 20 ℃, we measured the refractive index as a function of wavelength and recorded it in a table

Wavelength(nm)Refractive index(n)Wavelength(nm)Refractive index(n)
22004.087980004.0057
30004.045190004.004
38004.0267106004.0028
50004.016110004.0025
60004.0107120004.0021
70004.0079130004.0018

Conclusion

Single Germanium (Ge) crystals are ideal for laser lenses, windows and output coupling mirrors because of their good mechanical and thermal conductivity, as well as their low absorption at 10.6µm. They are also used as Ge substrate materials for various infrared filters.

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