NIR and uv femtosecond laser micro-structuring of materials

Photon06 Conference Manchester, Institute of Physics, OPD: Structured Optical Materials,
September 2006

W Perrie, A Baum, P Scully, M Sharp, S P Edwardson and K.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, sub-micron 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.