Product Code: ICAL05_P518

Intensity Modulated Focus: A Virtual 'Tool-Tip' for Femtosecond Laser Direct Writing
Authors:
K.J. Moh, Nanyang Technological University; Singapore
David K.Y. Low, Singapore Institute of Manufacturing Technology (SIMTech); Singapore
Y.Y. Tan, Nanyang Technological University; Singapore
Z.L. Li, Singapore Institute of Manufacturing Technology; Singapore
X.C. Yuan, Nanyang Technological University; Singapore
Presented at ICALEO 2005

Waveguides written in glass by femtosecond lasers using low numerical aperture (N.A.) and long focal length systems generally have an elliptical cross section owing to the elongated focal shape of such systems. The aspect ratio of the waveguides can be improved by redistributing the longitudinal intensity distribution around the focus with the aid of a diffractive element placed before the lens. The diffraction introduced competes with the extent of focusing by the lens to influence the final 3-dimensional shape of the focus. It is thus possible to optimize the required element dimensions with a given N.A system to give a near perfect aspect ratio for the written waveguides. We theoretically and experimentally investigate the relationship between the focus shape and intensity distribution at the focus in 2-dimensions to arrive at a set of optimum dimensions for a given NA and focal length system.