Pulse Burst Generation and Diffraction with Spatial Light Modulators for Dynamic Ultrafast Laser Materials Processing

Area of Science:

• Optics and Photonics
• Materials Science
• Laser Processing

Background:

• Ultrafast laser systems are crucial for advanced material processing.
• Controlling polarization and spatial distribution of laser pulses is key for precision micro-structuring.
• Existing methods often lack the flexibility for simultaneous, independent multi-beam processing.

Purpose of the Study:

• To develop a pulse burst optical system for enhanced laser material processing.
• To enable independent modulation and control of individual pulses within a burst.
• To demonstrate simultaneous multi-spot surface micro-structuring with controlled polarization.

Main Methods:

• Development of a pulse burst optical system using a delay line, beam-splitting polarizers, mirrors, and waveplates.
• Transformation of a single high-energy pulse into a burst with orthogonal linear polarizations.
• Utilizing two phase-only Spatial Light Modulators (SLMs) with orthogonal directors and hybrid Computer Generated Holograms (CGHs) for independent pulse modulation.
• Synchronizing scan motion and CGH application for real-time processing.

Main Results:

• Successfully generated pulse bursts with 323 MHz intra-burst frequency at a 5 kHz repetition rate.
• Demonstrated simultaneous multi-spot periodic surface micro-structuring on stainless steel.
• Achieved processing with orthogonal linear polarizations and cylindrical vector (CV) beams (Radial and Azimuthal).
• Observed reduced ablation rates on stainless steel with pulse bursts compared to standard 5 kHz processing due to plasma absorption dynamics.
• Showcased simultaneous independent multi-beam real-time processing using synchronized scan motion and CGH application.

Conclusions:

• The developed pulse burst optical system offers enhanced flexibility for parallel beam surface micro-structuring.
• Independent control over pulse polarization and spatial distribution is achieved.
• The technique allows for adaptive optics integration, paving the way for advanced laser manufacturing applications.