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M. Rafique, S. Bashir, A. Ajami, W. Husinsky, A. Hobro, B. Lendl:
"Atomic force microscopy, Raman spectroscopy and nonlinear absorption properties of femtosecond laser irradiated CR-39";
Applied Physics A: Materials Science & Processing, 101 (2010), 3; 551 - 554.

Investigations have been performed to explore ultrashort
laser irradiation effects on the surface topography
as well as structural and nonlinear absorption properties of a
polymer CR-39. For this purpose, a CR-39 target was exposed
in air to 25 fs, 800 nm Ti:sapphire laser radiation
at fluences ranging from 0.25 J cm−2 to 3.6 J cm−2. The
surface features, structural changes and nonlinear absorption
were explored by AFM, Raman Spectroscopy and a
Z-scan technique, respectively. Several topographical structures
like bumps, explosions and nano cavities have been
observed on the irradiated surface. Raman spectroscopy reveals
changes in the fundamental structure of the polymer
after the irradiation. Nonlinear absorption data contained by
the Z-scan technique predict the dominance of three-photon
absorption in case of pristine CR-39. Furthermore, nonlinear
absorption (three or two photon) increases with increasing
laser fluences and is well correlated with surface and structural
changes revealed by AFM and Raman spectroscopy.