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Optical Engineering

Mechanism and experimental study on three-dimensional facula shaping in femtosecond laser micromachining
Author(s): Xuetao Pan; Dawei Tu; Jianwen Cai
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Paper Abstract

Because of the laser beam waist and diffraction effect of the lens, the focal spot light field in femtosecond laser microprocessing has an ellipsoidal spatial distribution. This leads to the gap between two processing layers increasing along the axial direction, and the distribution density of processing points decreasing along the horizontal direction. This directly reduces the resolution of the microprocessing, and badly affects the machining accuracy and surface quality. We established a mathematical model for three-dimensional (3-D) laser beam shaping based on the Fresnel diffraction theory and designed a kind of four-ring complex amplitude transmittance phase plate by using a global optimization algorithm and genetic algorithm to simultaneously realize transverse and axial 3-D shaping. We numerically showed that the transverse and axial gains of the focal facula after 3-D shaping are 0.77 and 0.68, respectively, where the corresponding peak energy ratio is 0.36, the transverse and axial sidelobe energies are 0.28 and 0.62, respectively, and the defocusing amount is −0.08. We also constructed a confocal/two-photon microscope system to experimentally achieve a better shaping effect in the case of femtosecond laser fabrication at a point on the thin film of a photochromic material.

Paper Details

Date Published: 20 October 2015
PDF: 9 pages
Opt. Eng. 54(10) 105111 doi: 10.1117/1.OE.54.10.105111
Published in: Optical Engineering Volume 54, Issue 10
Show Author Affiliations
Xuetao Pan, Shanghai Univ. (China)
Changzhou Institute of Technology (China)
Dawei Tu, Shanghai Univ. (China)
Jianwen Cai, Changzhou Institute of Technology (China)

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