Simultaneous formation of ablative and thermochemical laser-induced periodic surface structures on Ti film at femtosecond irradiation

Formation of laser-induced periodic surface structures (LIPSS) on the titanium surface at the presence of sharply focused fs radiation exhibits two different regimes. Conventional ablative LIPSS with low regularity are oriented orthogonally to the polarization direction of the incident beam, while thermochemical LIPSS with highly uniform periodicity are oriented along the polarization direction. These two types of LIPSS can co-exist and influence each other for arbitrary polarization and beam scanning directions. The observed regimes help to clarify mechanisms of LIPSS formation, as well as to form LIPSS of specific shapes and degrees of regularity. (letter)