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DS: Dünne Schichten

DS 10: Laserverfahren II

DS 10.4: Vortrag

Dienstag, 27. März 2001, 12:00–12:15, S 5.1

Modification of dielectric surfaces with ultra short laser pulses — •Matthias Henyk, Florenta Costache, and Jürgen Reif — LS Experimentalphysik II, Brandenburgische Technische Universität Cottbus, Universitätsplatz 3-4, D-03044 Cottbus, Germany

Single crystalline dielectrics (barium fluoride, sapphire, sodium chloride) are irradiated with near infrared femtosecond laser pulses at an intensity well below the single-pulse ablation threshold under vacuum conditions. After a dose of several 1000 laser pulses the morphology of the irradiated spot is studied ex-situ by optical and electron microscopy. The different target materials exhibit rather different behaviour: In the case of barium fluoride, frozen surface waves with a modulation depth ranging from tenth to hundreds of nanometers are observed inside the crater. At few spots, columns are created, up to a few hundred nanometers high. At high magnification, an additional ripple-like fine structure is observed. On sapphire, the regular fine structure is present, but no other simple regular structures. In agreement with earlier results from other groups about the nanosecond laser pulse ablation from sodium chloride, the femtosecond pulse erosion is dominated by mechanical crack formation and steps. The results are discussed in correlation to out measurements of the ion and electron emission by time-of-flight mass spectrometry.