High power femtosecond fiber chirped pulse amplification system for high speed micromachining

Abstract

The need for improved precision in a wide variety of micromachining applications has driven scientific interest in ultrashort pulse lasers. Despite numerous demonstrations of reduced heat effect and improved processing quality, the utility of such lasers has been limited by the heavy demands placed upon laser performance. In addition to high contrast laser pulses with minimal pulse-to-pulse fluctuation, an ultrashort pulse laser must provide near diffraction-limited beam quality and robust long-term laser operation with high repetition rate for high processing speeds. We report here on a research prototype, high power femtosecond fiber chirped pulse amplification system. The system produces compressed pulses with energies > 50 μJ at > 15 W with M2 < 1.4. The use of cubicon pulses, i.e. stretched pulses with cubical spectral and temporal shape, enables pulse compression to < 500 fs with > 1000:1 temporal contrast despite significant self-phase modulation during amplification corresponding to a nonlinear phase delay of ~6pπ. As a demonstration of high speed femtosecond micromachining, we drill and cut 0.5-mm thick metal, semiconductor and dielectric targets.