Trimming method for a high-yield manufacturing of high-efficiency diffraction gratings

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Technology

Background:

• Fabricating dielectric diffraction gratings with high diffraction efficiency (DE) over a specific spectral bandwidth is challenging.
• Leaky-mode resonance gratings require precise manufacturing tolerances for optimal performance.

Purpose of the Study:

• To develop a fabrication method for precise control over the spectral bandwidth of high-efficiency dielectric diffraction gratings.
• To enhance the manufacturing process for diffraction gratings used in laser systems.

Main Methods:

• Implemented a two-step etching approach: initial dry anisotropic etching followed by iterative isotropic wet etching (KOH, 90°C).
• Utilized alkaline solution (KOH) for precise adjustment of grating parameters to tailor DE as a function of wavelength.

Main Results:

• Achieved high diffraction efficiencies (DEs) of 99.7±0.2% at 1030 nm in the -1st diffraction order.
• Demonstrated DEs exceeding 99% across a broad spectral range (1020-1070 nm).
• Integrated gratings as cavity end mirrors in an Yb:YAG thin-disk laser, yielding 145 W output power (M²<1.1).

Conclusions:

• The two-step etching method provides excellent control over spectral bandwidth and DE for dielectric diffraction gratings.
• This fabrication technique enables high-performance optical components for advanced laser systems.
• The developed gratings are suitable for high-power laser applications, as demonstrated with the Yb:YAG thin-disk laser.