Correlation between He-Ne scatter and 2.7-microm pulsed laser damage at coating defects

Area of Science:

• Materials Science
• Optical Engineering
• Laser Physics

Background:

• A correlation between defect-initiated pulsed laser damage and local predamage scatter in multilayer infrared mirror coatings has been reported.
• This phenomenon is crucial for understanding optical coating reliability.

Purpose of the Study:

• To analyze in detail the correlation between defect-initiated pulsed laser damage and local predamage scatter in multilayer infrared mirror coatings.
• To confirm previous findings using a larger dataset and varied conditions.

Main Methods:

• Utilized a He-Ne scatter probe to detect scatter signals from individual undamaged defects.
• Performed damage frequency measurements (1-on-1) using 100-ns pulses at 2.7-microm wavelength.
• Compared scatter signals with damage initiation sites and analyzed focal spot intensity profiles.

Main Results:

• Confirmed a strong correlation between increased predamage scatter signals and higher damage frequency.
• Demonstrated equivalence in defect densities indicated by scatter and damage probes.
• Identified conditions limiting the correlation, such as variable scatter and background scatter.

Conclusions:

• The study confirms the link between defect scatter and laser-induced damage in infrared mirror coatings.
• Results suggest scatter probes are viable for nondestructive defect detection.
• Findings have implications for improving optical coating quality control and reliability.