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Proceedings Paper

Femtosecond laser-induced periodic surface structures: recent approaches to explain their sub-wavelength periodicities
Author(s): Jörn Bonse; Arkadi Rosenfeld; Jörg Krüger
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Paper Abstract

The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of semiconductors and dielectrics by linearly polarized high-intensity Ti:sapphire fs-laser pulses (τ ~100 fs, λ ~800 nm) is studied experimentally and theoretically. In the experiments, two different types of LIPSS exhibiting very different spatial periods are observed (socalled LSFL - low spatial frequency LIPSS, and HSFL - high spatial frequency LIPSS), both having a different dependence on the incident laser fluence and pulse number per spot. The experimental results are analyzed by means of a new theoretical approach, which combines the generally accepted LIPSS theory of J. E. Sipe and co-workers [Phys. Rev. B 27, 1141-1154 (1983)] with a Drude model, in order to account for transient changes of the optical properties of the irradiated materials. The joint Sipe-Drude model is capable of explaining numerous aspects of fs-LIPSS formation, i.e., the orientation of the LIPSS, their fluence dependence as well as their spatial periods. The latter aspect is specifically demonstrated for silicon crystals, which show experimental LSFL periods Λ somewhat smaller than λ. This behaviour is caused by the excitation of surface plasmon polaritons, SPP, (once the initially semiconducting material turns to a metallic state upon formation of a dense free-electron-plasma in the material) and the subsequent interference between its electrical fields with that of the incident laser beam, resulting in a spatially modulated energy deposition at the surface. Upon multi-pulse irradiation, a feedback mechanism, caused by the redshift of the resonance in a grating-assisted SPP excitation, is further reducing the LSFL spatial periods. The SPP-based mechanism of LSFL successfully explains the remarkably large range of LSFL periods between ~0.6 λ and λ.

Paper Details

Date Published: 7 February 2011
PDF: 10 pages
Proc. SPIE 7994, LAT 2010: International Conference on Lasers, Applications, and Technologies, 79940M (7 February 2011); doi: 10.1117/12.879813
Show Author Affiliations
Jörn Bonse, Bundesanstalt für Materialforschung und -prüfung (Germany)
Arkadi Rosenfeld, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany)
Jörg Krüger, Bundesanstalt für Materialforschung und -prüfung (Germany)

Published in SPIE Proceedings Vol. 7994:
LAT 2010: International Conference on Lasers, Applications, and Technologies
Vladislav Panchenko; Gérard Mourou; Aleksei M. Zheltikov, Editor(s)

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