Femtosecond laser-induced periodic surface structures: recent approaches to explain their sub-wavelength periodicities

Jörn Bonse; Arkadi Rosenfeld; Jörg Krüger

doi:10.1117/12.879813

7 February 2011 Femtosecond laser-induced periodic surface structures: recent approaches to explain their sub-wavelength periodicities

Jörn Bonse, Arkadi Rosenfeld, Jörg Krüger

Author Affiliations +

Proceedings Volume 7994, LAT 2010: International Conference on Lasers, Applications, and Technologies; 79940M (2011) https://doi.org/10.1117/12.879813
Event: International Conference on Coherent and Nonlinear Optics (ICONO 2010) and International Conference on Lasers, Applications and Technologies (LAT 2010), 2010, Kazan, Russian Federation

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.

Citation Download Citation

Jörn Bonse, Arkadi Rosenfeld, and Jörg Krüger "Femtosecond laser-induced periodic surface structures: recent approaches to explain their sub-wavelength periodicities", Proc. SPIE 7994, LAT 2010: International Conference on Lasers, Applications, and Technologies, 79940M (7 February 2011); https://doi.org/10.1117/12.879813

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