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S. Bashir, M. Rafique, W. Husinsky:
"Femtosecond laser-induced subwavelength ripples on Al, Si, CaF₂ and CR-39";
Nuclear Instruments & Methods in Physics Research Section B, 275 (2012), 1 - 6.

The formation of self-organized subwavelength ripples on Al, Si, CaF2 and CR-39 induced by 25 fs laser
pulses at central wavelength of 800 nm has been observed under certain experimental conditions. In case
of Al subwavelength gratings with periodicities ranging from 20 to 220 nm are reported. For CaF2 the
periodicity goes up to 625 nm. In case of Si, nano-gratings have the periodicity of 10-100 nm. The interspacing
of these gratings is 60 nm in case of CR-39. These features which are significantly shorter than
incident laser wavelength are observed at the irradiation fluence slightly higher than the ablation threshold
regardless of the target material. In addition to these nanoripples, classical or microripples with an
average spacing of 1-2 lm have also been registered on irradiated surfaces of Al and Si. These microripples
have appeared at fluence higher than that is required for nanoripple-formation. It has been found
that the formation of the laser-induced ripples is strongly dependent and quite sensitive to the incident
laser fluence and the selection of material.

fs Laser LIPSS Al Si CaF2 CR-39