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FEMTOSECOND LASER MICRO-STRUCTURING OF MATERIALS IN THE NIR AND UV REGIME
ICALEO® 2007 Congress Proceedings, Laser Microprocessing Conference
Paper M103 pp12-18
IBSN: 13#978-0-912035-88-8 & 10#0-912035-88-9
D. Liu, J. Cheng, W. Perrie, A. Baum, P. Scully, M. Sharp, S. P. Edwardson, Z. Kuang, N. G. Semaltianos, P. French, G. Dearden, L .Li, K. G. Watkins
Abstract: Ultrafast laser micro-structuring of ceramic alumina, titanium and stainless steel are presented confirming that precision, melt free micro-structuring is indeed possible with intense femtosecond optical pulses. While metals are best machined at a fluence a few times ablation threshold, ceramic alumina, on the other hand, shows excellent structuring with no evidence of melt at high fluence F ~ 21Jcm-2. In PMMA, at 387nm with pulselength ~ 200fs, we demonstrate refractive index modification within the bulk induced by two photon absorption to generate phase gratings. By using a holographic technique combined with 387nm femtosecond radiation and 0.5NA UV objective, submicron pitch periodic structures were ablated on stainless steel, titanium and silicon. With a lower (0.15NA) objective and focussing the periodic optical field distribution within bulk PMMA, micron pitch phase gratings can be generated.
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