Diffractive multi-beam surface micro-processing using 10 ps laser pulses

Applied Surface Science 255 (2009) 9040–9044

Zheng Kuang, Walter Perrie, Dun Liu, Stuart Edwardson, Jian Cheng, Geoff Dearden, Ken Watkins

A high repetition rate picosecond laser system is combined with a spatial light modulator (SLM) for diffractive multiple beam processing. The effect of the zero order beam is eliminated by adding a Fresnel zone lens (FZL) to defocus the un-diffracted beamat the processing plane. Chromatic dispersion, which is evident with a large bandwidth femtosecond pulses leading to the problem of distorted hole shape is eliminated due to the much narrower spectral bandwidth, ~0.1 nm at 10 ps pulselength, resulting in highly uniform intensity spots, independent of diffraction angle. In addition, high-throughput processing is demonstrated by combining the high power laser output, 2.5W at l  1064 nm and fast repetition rate, f  20 kHz with P > 1.2W diffracted into 25 parallel beams. This has the effect of creating an ‘‘effective’’ repetition rate of 500 kHz without restrictive scan speeds.