High-brightness solid state laser systems with fiber phase conjugate mirrors for micro material processing

Abstract

High beam quality is one of the most important properties for micro material processing with lasers. It facilitates slight focus diameters and due to high Raleigh length even at strong focusing drilling of holes with high aspect ratio. Together with high average output powers it allows fast processes with high quality. Another important point is the wavelength of the laser radiation. Many materials e.g. diamond or silicon show no sufficient absorption at fundamental wavelength of Nd based solid-state laser sources. Frequency conversation to the second and fourth harmonic allows the efficient processing of these materials. At least flexible pulse peak power and repetition rate is necessary to optimize the process. Three laser systems which fulfill these requirements are investigated. A pulsed pumped Nd:YAG System which delivers an average output power of 315 W with M² = 2.6 at the fudamental wavelength and 124 W at the second harmonic. Another pulsed pumped System based on Nd:YAG with an average output power up to 125 W with M² = 2.2 at the fundamental wavelength, 49.5 W at the second harmonic and 4.75 W at 266 nm. Due to its active Q-switch the pulse peak power of this system is variable in a wide range. Furthermore, a continuously pumped amplifier arrangement with nearly diffraction limited output of 120 W average power has been achieved at 10 kHz repetition rate.