Polymer like response of muscovite upon 515 nm femtosecond laser pulse processing

Muscovite, a nanolayered transparent crystalline dielectric, is shown to respond like a polymer upon irradiation with a single 190 fs duration laser pulse, at a wavelength of 515 nm, for a range of fluences (1.4–6.4 J/cm²). Laser-pulse-modified sites were characterized using field emission scanning electron microscopy (FESEM). Cavitation and bubbling are observed in the laser processed region similar to previous observations in poly-methyl-methacrylate (PMMA). The diameter of these sites is consistent with the standard model commonly applied in laser ablation studies. These polymer-like results at 515 nm are in contrast to the response of muscovite exposed to a 150-fs single laser pulse at 800 nm for a similar range of fluences. Where a diverse range of topologies was observed as the fluence was increased. Additionally, we also report an absorption band edge at ~4 eV (for the muscovite sheet used in the study). This is lower than the previously reported band gap energy value of 7.8 eV. We propose that the differences observed at the two wavelengths are primarily due to either 2 or 3 photons being required for nonlinear photoionization and the impact of the mineral water content of muscovite (4.7 wt%).