High laser-resistant multilayer mirrors by nodular defect planarization [invited].

Area of Science:

• Materials Science
• Optics
• Laser Technology

Background:

• Optical interference mirror coatings are crucial for laser systems.
• Substrate surface defects, such as particles, act as microlenses, intensifying light and leading to coating failure.
• Existing mirror coatings exhibit limited laser resistance due to these defect-induced stress points.

Purpose of the Study:

• To investigate the effect of substrate defect planarization on the laser resistance of 1053 nm mirror coatings.
• To quantify the improvement in laser damage threshold after defect reduction.
• To develop a method for mitigating defect-induced light intensification in optical coatings.

Main Methods:

• Utilized a discrete process involving angle-dependent ion etching to reduce defect cross-sectional area.
• Employed unidirectional ion-beam deposition in conjunction with etching to further refine defect morphology.
• Tested the laser resistance of treated and untreated mirror coatings using 10 ns laser pulses at 1053 nm.

Main Results:

• Substrate defect planarization reduced defect cross-sectional area by over 90%.
• Laser resistance of the treated 1053 nm mirror coatings exceeded 100 J/cm2.
• This represents a 20-fold increase in laser resistance compared to untreated coatings.

Conclusions:

• Substrate defect planarization is a highly effective method for enhancing the laser resistance of optical mirror coatings.
• The developed ion etching and deposition technique significantly mitigates the detrimental effects of substrate defects.
• This advancement has critical implications for improving the durability and performance of optical components in high-power laser applications.