Irregular LIPSS produced on metals by single linearly polarized femtosecond laser

Abstract

Currently, supra-wavelength periodic surface structures (SWPSS) are only achievable on silica dielectrics and silicon by femtosecond (fs) laser ablation, while triangular and rhombic laser induced periodic surface structures (LIPSS) are achievable by circularly polarized or linear cross-polarized femtosecond laser. This is the first work to demonstrate the possibility of generating SWPSS on Sn and triangular and rhombic LIPSS on W, Mo, Ta, and Nb using a single linearly polarized femtosecond laser. We discovered, for the first time, SWPSS patches with each possessing its own orientation, which are completely independent of the light polarization direction, thus, breaking the traditional rules. Increasing the laser power enlarges SWPSS periods from 4–6 μm to 15–25 μm. We report a maximal period of 25 μm, which is the largest period ever reported for SWPSS, ∼10 and ∼4 times the maximal periods (2.4 μm/6.5 μm) of SWPSS ever achieved by fs and ns laser ablation, respectively. The formation of triangular and rhombic LIPSS does not depend on the laser (power) or processing (scan interval and scan methodology) parameters but strongly depends on the material composition and is unachievable on other metals, such as Sn, Al, Ti, Zn, and Zr. This paper proposes and discusses possible mechanisms for molten droplet generation/spread/solidification, Marangoni convection flow for SWPSS formation, and linear-to-circular polarization transition for triangular and rhombic LIPSS formation. Reflectance and iridescence of as-prepared SWPSS and LIPSS are characterized. It was found that besides insufficient ablation on W, the iridescence density of Ta-, Mo-, Nb-LIPSS follows the sequence of melting temperatures: Ta > Mo > Nb, which indicates that the melting temperature of metals may affect the regularity of LIPSS. This work may inspire significant interest in further enriching the diversity of LIPSS and SWPSS.

Diverse nanomaterials synthesized by laser ablation of pure metals in liquids

“…Owing to the invention of the laser system by Maiman [10] in 1960 and its continuous innovation with a milestone of chirped pulse amplification, ultrashort lasers with high powers and short pulse durations and increasingly low prices have become accessible to researchers, which open up many avenues for material processing, such as laser cutting [11], laser functional structuring [12][13][14][15][16], laser machining [17], laser cross-linking [18], 3D/4D laser printing [19][20][21], additive manufacturing [22], and laser patterning [23,24]. Unlike laser additive manufacturing and laser printing techniques that are aimed to construct 3D or 4D structures from smaller-scale building blocks, laser ablation is a subtractive manufacturing technique with micro/nanomaterials as the subtractive materials [11,25].…”

Impact of Pre-Patterned Structures on Features of Laser-Induced Periodic Surface Structures

“…On the other hand, as the LIPSS covered topography is the final step of a sequence of processes, a detailed investigation of complex multiscale physical mechanisms that include spatially modulated energy absorption from the material, electron excitation, relaxation processes phase transitions and resolidification is required [ 19 , 21 , 27 ]. On the other hand, the physical process that leads to the above topographies is based on the concept that upon relaxation a thin molten layer appears on the surface if laser conditions allow a phase transition; due to the spatial temperature gradient in the layer, strong instabilities are generated that produce fluid movement (i.e., Marangoni effects) and eventually upon re-solidification LIPSS are formed [ 15 , 19 , 23 , 28 , 29 , 30 , 31 , 32 ]. Therefore, the formation of HSFL or LSFL originates from a combination of (i) electromagnetic mechanisms that account for the orientation and define the spatially modulated deposited/absorbed energy and (ii) hydrodynamic effects that determine the features of the final topography.…”

Picosecond Bessel Beam Fabricated Pure, Gold-Coated Silver Nanostructures for Trace-Level Sensing of Multiple Explosives and Hazardous Molecules

“…Across the scientific community, numerous innovative approaches have been pursued in order to reach a high-flourishing upswing in optical responses of the nano-photonic systems in diverse terms. Aiming for such advancements in miscellaneous nano-scale optical features, such as fabrication of diverse nanoparticles (NPs) in liquids [1][2][3][4][5], exotic nanostructures (NSs) (in air/liquid) with desired plasmonic response, and attaining enhanced optical features, such as surface-enhanced Raman spectroscopy (SERS), significant improvisations have been undertaken in laser-matter interaction research. Implementation of non-Gaussian beam profile in laser ablation, and engagement of different off-axis geometrical optics has been quite significant.…”