Nanolaminate-based design for UV laser mirror coatings

Area of Science:

• Materials Science
• Optics
• Laser Technology

Background:

• Increasing laser power necessitates advanced ultraviolet (UV) coatings.
• Traditional UV mirror coatings struggle to balance high reflectivity, broad bandwidth, and laser resistance.
• Existing methods often involve layering laser-resistant materials onto highly reflective bases.

Purpose of the Study:

• To propose and demonstrate a novel "reflectivity and laser resistance in one" design for UV mirror coatings.
• To utilize tunable nanolaminate layers for improved optical properties and laser durability.
• To address the limitations of conventional coatings in high-power UV laser systems.

Main Methods:

• Development of a tunable nanolaminate layer design incorporating a high refractive index and large optical bandgap.
• Experimental fabrication of an aluminum oxide-hafnium oxide (Al2O3-HfO2) nanolaminate mirror coating using electron beam deposition.
• Characterization of the coating's reflectance bandwidth and laser-induced damage threshold.

Main Results:

• The Al2O3-HfO2 nanolaminate coating achieved a reflectance >99.5% over a bandwidth more than double that of traditional mirrors of similar thickness.
• The laser-induced damage threshold was enhanced by approximately 1.3 times for 7.6 nanosecond pulses at 355 nanometers wavelength.
• Demonstrated a viable "reflectivity and laser resistance in one" strategy.

Conclusions:

• The tunable nanolaminate approach offers a significant advancement over traditional UV mirror coatings.
• This new design strategy enables a new generation of UV coatings optimized for high-power laser applications.
• The Al2O3-HfO2 nanolaminate coating provides a promising solution for demanding UV laser environments.