Focus Tracking System for Femtosecond Laser Machining using Low Coherence Interferometry

Area of Science:

• Laser Machining and Optics
• Biomedical Engineering
• Materials Science

Background:

• Precise control of the focal plane is critical for high-resolution laser machining.
• Maintaining consistent laser-material interaction is challenging due to sample positioning variations.
• Existing methods for focus monitoring can be complex or intrusive.

Purpose of the Study:

• To develop a real-time focus tracking system for femtosecond laser machining.
• To utilize the inherent low coherence of the machining laser for position monitoring.
• To enhance the stability and accuracy of laser ablation processes.

Main Methods:

• A single-laser, real-time focus tracking system was designed.
• A Michelson Interferometer collected backscattered laser data from the ablation spot.
• Custom software analyzed data and controlled an XYZ automated translation stage for position correction.

Main Results:

• Stable etching of channels with consistent cross-section profiles was achieved on bovine tooth.
• The system maintained the sample within the confocal parameter during processing.
• The system demonstrated the capability to monitor crater depth evolution and assess material removal.

Conclusions:

• The developed focus tracking system significantly improves the stability of laser machining.
• This technology enables precise material processing with enhanced control over depth and profile.
• The system offers a practical solution for real-time monitoring and correction in laser ablation.