Highly ordered laser imprinted plasmonic metasurfaces for polarization sensitive perfect absorption.

We present polarization-sensitive gap surface plasmon metasurfaces fabricated with direct material processing using pulsed laser light, an alternative and versatile approach. In particular we imprint laser induced periodic surface structures on nanometer-thick Ni films, which are back-plated by a grounded dielectric layer with TiO2 and ZnO deposition followed by Au evaporation. The procedure results in a metal-insulator-metal type plasmonic metasurface with a corrugated top layer consisting of highly-ordered, sinusoidal shaped, periodic, thin, metallic nanowires. The metasurface sustains sharp, resonant gap surface plasmons and provides various opportunities for polarization control in reflection, which is here switched by the size and infiltrating material of the insulating cavity. The polarization control is associated with the polarization sensitive perfect absorption and leads to high extinction ratios in the near-IR and mid-IR spectral areas. Corresponding Fourier-transform infrared spectroscopy measurements experimentally demonstrate that the fabrication approach produces metasurfaces with very well-defined, controllable, sharp resonances and polarization sensitive resonant absorption response which, depending on the insulating cavity size, impacts either the normal or the parallel to the nanowires polarization.

Fabrication of Biomimetic 2D Nanostructures through Irradiation of Stainless Steel Surfaces with Double Femtosecond Pulses.

Femtosecond laser induced changes on the topography of stainless steel with double pulses is investigated to reveal the role of parameters such as the fluence, the energy dose and the interpulse delay on the features of the produced patterns. Our results indicate that short pulse separation (Δτ = 5 ps) favors the formation of 2D Low Spatially Frequency Laser Induced Periodic Surface Structures (LSFL) while longer interpulse delays (Δτ = 20 ps) lead to 2D High Spatially Frequency LIPSS (HSFL). The detailed investigation is complemented with an analysis of the produced surface patterns and characterization of their wetting and cell-adhesion properties. A correlation between the surface roughness and the contact angle is presented which confirms that topographies of variable roughness and complexity exhibit different wetting properties. Furthermore, our analysis indicates that patterns with different spatial characteristics demonstrate variable cell adhesion response which suggests that the methodology can be used as a strategy towards the fabrication of tailored surfaces for the development of functional implants.