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Proceedings Paper

Simultaneous spatial and temporal focusing: a route towards confined nonlinear materials processing
Author(s): Robert Kammel; Klaus Bergner; Jens Thomas; Roland Ackermann; Stefan Skupin; Stefan Nolte
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Paper Abstract

Ultrashort pulse lasers enable reliable and versatile high precision ablation and surface processing of various materials such as metals, polymers and semiconductors. However, when modifications deep inside the bulk of transparent media are required, nonlinear pulse material interactions can decrease the precision, since weak focusing and the long propagation of the intense pulses within the nonlinear media may induce Kerr self-focusing, filamentation and white light generation. In order to improve the precision of those modifications, simultaneous spatial and temporal focusing (SSTF) allows to reduce detrimental nonlinear interactions, because the ultrashort pulse duration is only obtained at the focus, while outside of the focal region the continuously increasing pulse duration strongly reduces the pulse intensity.

In this paper, we review the fundamental concepts of this technology and provide an overview of its applications for purposes of multiphoton microscopy and laser materials processing. Moreover, numerical simulations on the nonlinear pulse propagation within transparent media illustrate the linear and nonlinear pulse propagation, highlighting the differences between conventional focusing and SSTF. Finally, fs-laser induced modifications in gelatine are presented to compare nonlinear side-effects caused by conventional focusing and SSTF. With conventional focusing the complex interplay of self-focusing and filamentation induces strongly inhomogeneous, elongated disruptions. In contrast, disruptions induced by SSTF are homogeneously located at the focal plane and reduced in length by a factor >2, which is in excellent agreement with the numerical simulations of the nonlinear pulse propagation and might favor SSTF for demanding applications such as intraocular fs-laser surgery.

Paper Details

Date Published: 4 March 2016
PDF: 10 pages
Proc. SPIE 9736, Laser-based Micro- and Nanoprocessing X, 97360T (4 March 2016); doi: 10.1117/12.2209540
Show Author Affiliations
Robert Kammel, Friedrich-Schiller-Univ. Jena (Germany)
Klaus Bergner, Friedrich Schiller Univ. Jena (Germany)
Jens Thomas, Friedrich-Schiller-Univ. Jena (Germany)
Roland Ackermann, Friedrich-Schiller-Univ. Jena (Germany)
Stefan Skupin, Univ. de Bordeaux, CNRS, CEA, Ctr. Lasers Intenses et Applications (France)
Stefan Nolte, Friedrich-Schiller-Univ. Jena (Germany)
Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)

Published in SPIE Proceedings Vol. 9736:
Laser-based Micro- and Nanoprocessing X
Udo Klotzbach; Kunihiko Washio; Craig B. Arnold, Editor(s)

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