High-speed processing with ultrafast lasers and resonant scanning systems

Abstract

Ultrafast lasers supplying highest average powers, pulse energies and pulse repetition rates require adequate system technology for high throughput and high quality laser processing. Depending on the application, multi-beam processing and/or high-speed scanning for fast beam deflection are required. Diffractive optical elements are used for beam splitting. Galvanometer scanners show high-performance at pulse repetition frequencies (PRF) up to a few MHz and polygon scanners provide high-speed scanning at even higher PRF for large surface processing. However, efficient line-oriented surface processing of small patterns using PRF in the MHz range cannot be achieved by existing scanning system technology. New resonant scanning systems have the potential to close this gap between galvanometer and polygon scanning with highest beam deflection speeds due to their oscillation frequencies in the kHz range and high duty cycles for all patterns. In addition to the high-speed scanning capabilities, resonant scanners can also enable new applications like ultrashort pulse laser (USPL) surface welding by moving the focused laser beam ultrafast along defined contours, inducing melting layers by heat accumulation. This publication describes the principles of high-speed processing with high power, high PRF ultrafast lasers in combination with high-speed resonant scanning systems. Potential applications and experimental results will be discussed like cutting, two-dimensional surface processing and functionalization, or welding applications. Moreover, a new approach is proposed to convert the nonlinear sinusoidal scanning of resonant systems into linear scanning by a spatially varying modulation of the unfocused laser beam.