Laser-Material Interactions of High-Quality Ultrashort Pulsed Vector Vortex Beams

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Physics

Background:

• Spatial light modulators (SLMs) enable dynamic control of light polarization.
• Cylindrical vector beams offer unique polarization properties for laser applications.
• Laser-induced periodic surface structures (LIPSS) are important for material modification.

Purpose of the Study:

• To generate uniform multiple cylindrical vector beams with radial and azimuthal polarizations.
• To investigate the application of these beams for laser ablation and surface structuring.
• To evaluate the vector purity and spatial uniformity of the generated beams.

Main Methods:

• Utilized binary Dammann gratings (1 × 5 and 2 × 2) with an SLM and a nanostructured S-wave plate.
• Generated multiple cylindrical vector beams with high vector purity (concurrence C = 0.95 ± 0.02).
• Applied beams to ablate Ti-6Al-4V metal samples, forming LIPSS and analyzing ablation thresholds.

Main Results:

• Achieved uniform multiple cylindrical vector beams with radial and azimuthal polarizations.
• Confirmed polarization states via LIPSS formation on titanium alloy.
• Demonstrated comparable ablation thresholds to Gaussian modes and consistent thresholds for varying orbital angular momentum (OAM) beams.
• Verified high spatial uniformity (cosθ > 0.96 for 1 × 5, 0.92 for 2 × 2 arrays) using machine learning (cosine similarity).

Conclusions:

• Diffractive multi-beams generated using Dammann gratings and SLMs are effective for creating uniform cylindrical vector beams.
• These beams enable precise laser ablation and LIPSS formation on metal surfaces with high vector purity.
• Beam scanning with ring modes enhances micro-structuring throughput and uniformity for industrial applications.