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Theoretical Calculation and Experimental Verification for Dislocation Reduction in Germanium Epitaxial Layers with Semicylindrical Voids on Silicon
Published on: July 17, 2020
Refractive index changes in germanium due to intense radiation
Applied Optics
|March 4, 2010
Summary
High-power laser pulses alter germanium's refractive index primarily through heating, causing significant temperature increases. Surface diffraction gratings form, affecting reflectivity without degradation from transverse diffusion.
Area of Science:
- Materials Science
- Optics
- Solid State Physics
Background:
- Understanding the optical properties of semiconductors under intense laser irradiation is crucial for optoelectronic device applications.
- Germanium's response to high-intensity light dictates its suitability for laser-based technologies.
Purpose of the Study:
- To measure the changes in the real and imaginary parts of germanium's refractive index.
- To investigate the effects of high incident power on germanium's optical properties.
- To analyze the formation and behavior of laser-induced surface diffraction gratings.
Main Methods:
- Measurements of the refractive index of germanium at 6943 Å.
- Exposure to incident laser power up to 5 MW/cm².
- Analysis of surface diffraction grating formation and transverse diffusion effects.
Main Results:
- The primary cause of refractive index change for nanosecond pulses is thermal heating, with temperature increases up to 350°C.
- A diffraction grating is formed on the germanium surface by beam interference, altering reflectivity.
- Transverse diffusion effects do not degrade the effectiveness of the grating for a 20 µm spacing.
Conclusions:
- High-power laser pulses induce significant thermal effects in germanium, altering its optical properties.
- Laser-induced surface gratings play a role in germanium's reflectivity changes.
- The effectiveness of these gratings is maintained against transverse diffusion.
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