High-efficiency dielectric reflection gratings: design, fabrication, and analysis

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Technology

Background:

• Conventional metal gratings limit laser damage thresholds in high-power laser systems.
• Dielectric gratings offer a potential solution to enhance laser-induced damage resistance.

Purpose of the Study:

• To design and fabricate all-dielectric reflection gratings with enhanced laser damage thresholds.
• To investigate the performance of dielectric gratings for chirped-pulse-amplification (CPA) systems.

Main Methods:

• A combination of dielectric mirror and corrugated top layer was designed for optimal performance.
• Binary dielectric gratings were optimized theoretically for 100% reflectivity.
• Electron-beam lithography and sputtering techniques were used for fabrication on a fused-silica substrate.

Main Results:

• Theoretical 100% reflectivity was achieved for the -1 order in Littrow mounting at a 45-degree angle of incidence.
• Fabricated gratings demonstrated 97% diffraction efficiency in the -1 order.
• Measured laser damage thresholds reached 4.4 J/cm² (5-ns pulses) and 0.18 J/cm² (1-ps pulses) at 532 nm.

Conclusions:

• All-dielectric gratings significantly enhance laser damage thresholds compared to metal gratings.
• The developed dielectric gratings are suitable for high-power laser applications, including CPA.
• The design and fabrication methods provide a pathway for advanced optical grating development.