Single-pulse ablation of multi-depth structures via spatially filtered binary intensity masks

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Technology

Background:

• Digital micromirror devices (DMDs) are typically used as binary intensity masks in laser machining due to pixel switching speed limitations.
• Standard DMD applications restrict intensity modulation to simple "on" or "off" states for each pixel.

Purpose of the Study:

• To demonstrate a method for achieving near-continuous intensity control using DMDs in laser machining.
• To maintain high-precision laser-machining resolution while enabling complex feature fabrication.

Main Methods:

• Exploiting the numerical aperture of the optical system during the design of binary masks for DMDs.
• Utilizing 150 fs laser pulses for ablation on nickel substrates.

Main Results:

• Achieved near-continuous intensity control by optimizing binary mask design with optical system's numerical aperture.
• Successfully produced complex features with ablation depths up to ~60 nm in single laser pulses.
• Maintained high lateral resolution of ~2.5 μm during laser ablation.

Conclusions:

• DMDs can be effectively utilized for high-precision laser machining with grayscale-like intensity control.
• The proposed method expands the capabilities of DMDs for advanced material processing and microfabrication.