Laser energy absorption prediction of silicon substrate surface from a mid- and high-spatial frequency error

Area of Science:

• Optical Engineering
• Materials Science
• Laser Physics

Background:

• High-energy laser systems development is limited by optical element energy absorption.
• Accurate and cost-effective absorption testing is essential for engineering applications.
• Existing roughness-induced absorption (RIA) theories do not fully correlate with measured surface errors.

Purpose of the Study:

• To develop a more accurate method for predicting laser energy absorption in optical elements.
• To optimize the definition of roughness-induced absorption (RIA) by incorporating spatial error characteristics.
• To enable semi-quantitative prediction of substrate absorption in high-energy optics.

Main Methods:

• Investigated the relationship between surface spatial error and laser energy absorption.
• Optimized the roughness-induced absorption (RIA) theory to spatial error-induced absorption (SEIA).
• Defined SEIA as proportional to the square of mid- and high-spatial frequency errors within a specific range.

Main Results:

• Identified three key influencing factors for absorption prediction.
• Established that SEIA depends on laser diameter, wavelength, and coating properties.
• Classified total absorption into SEIA and background absorption (BGA), with BGA determined by material and process.

Conclusions:

• The developed SEIA model provides a predictable method for estimating total absorption by combining SEIA and BGA.
• This approach allows for semi-quantitative prediction of substrate absorption in high-energy optics.
• SEIA offers a novel perspective for researching element-absorbed laser energy in high-power laser technologies.