Creation of azimuthally and radially directed laser-induced periodic structures on large tantalum surface

The formation of well-controlled nano/micrometer-sized structures on metallic surfaces enables the modification of their optical and wetting properties. Forming such structures on the surface of biocompatible materials, in particular, can expand their applications in various areas of science and technology. Here we present results on covering tantalum (Ta), a biocompatible material, with complex nanosized structures comprising azimuthally- and radially-directed laser-induced periodic surface structures (LIPSS) by rotating the metallic sample with respect to the polarization direction of the irradiating laser pulses. For the first time, we use a high-repetition rate (150 kHz) fiber-based laser with 37 fs ablating pulses and a central wavelength of 1030 nm to form ripples that are directed both parallel and perpendicular to the laser polarization direction on the surface of Ta. Rotating the target during ablation led to forming two distinct zones of structures. The first zone, around the circumference of the target, consisted of both high- and low-spatial-frequency LIPSS, while in the second zone, at the center of the target, was covered by nanoparticles redeposition. We demonstrate how the formation of such complex structures significantly alters the optical reflectance and wetting characteristics of Ta. (paper)