► Black silicon is produced by direct femtosecond laser surface structuring. ► In the visible, the reflectance of the blackened surface is less than 5%. ► Low reflectance of black silicon extends to ...mid-infrared wavelengths. ► Created black silicon is mechanically robust.
Using a direct femtosecond laser surface structuring technique, an array of equally spaced parallel nanostructure-textured microgrooves on silicon was produced that causes a dramatic reduction of the treated silicon reflectance. The processed area appears velvet black at all viewing angles. Throughout the visible region, the reflectance of the blackened surface is less than 5%. The antireflection effect of the processed surface also extends to the mid-infrared wavelength range. Furthermore, this technique has a potential in reducing silicon reflectance at terahertz frequencies and even in millimeter wavelength range.
In this study we perform the first femtosecond laser surface treatment of titanium in order to determine the potential of this technology for surface structuring of titanium implants. We find that ...the femtosecond laser produces a large variety of nanostructures (nanopores, nanoprotrusions) with a size down to 20
nm, multiple parallel grooved surface patterns with a period on the sub-micron level, microroughness in the range of 1–15
μm with various configurations, smooth surface with smooth micro-inhomogeneities, and smooth surface with sphere-like nanostructures down to 10
nm. Also, we have determined the optimal conditions for producing these surface structural modifications. Femtosecond laser treatment can produce a richer variety of surface structures on titanium for implants and other biomedical applications than long-pulse laser treatments.
Following direct femtosecond laser pulse irradiation, we produce a unique grating structure over a large area superimposed by finer nanostructures on a silicon wafer. We study, for the first time, ...the antireflection effect of this femtosecond laser-induced periodic surface structures (FLIPSSs) in the wavelength range of 250 - 2500 nm. Our study shows that the FLIPSSs suppress both the total hemispherical and specular polarized reflectance of silicon surface significantly over the entire studied wavelength range. The total polarized reflectance of the processed surface is reduced by a factor of about 3.5 in the visible and 7 in the UV compared to an untreated sample. The antireflection effect of the FLIPSS surface is broadband and the suppression stays to the longest wavelength (2500 nm) studied here although the antireflection effect in the infrared is weaker than in the visible. Our FLIPSS structures are free of chemical contamination, highly durable, and easily controllable in size.
Using high-intensity femtosecond laser pulses, we create a novel surface pattern that transforms regular silicon to superwicking. Due to the created surface structure, water sprints vertically uphill ...in a gravity defying way. Our study of the liquid motion shows that the fast self-propelling motion of water is due to a supercapillary effect from the surface structures we created. The wicking dynamics in the produced surface structure is found to follow the classical square root of time dependence.
In this paper, we report on various nanostructures produced through direct surface modification on metals using femtosecond laser pulses. We show, for the first time, that these nanosctructures are ...natural consequence following femtosecond laser ablation. The optimal conditions for producing various nanostructures are determined.
By applying the femtosecond laser blackening technique directly to a tungsten incandescent lamp filament, we dramatically brighten the tungsten lamp and enhance its emission efficiency to approach ...100%. A comparison study of emission and absorption for the structured metal surfaces shows that Kirchhoff's law is applicable for the black metal. Furthermore, we demonstrate that we can even obtain partially polarized light as well as control the spectral range of the optimal light emission from the laser-blackened tungsten lamp.
Through femtosecond laser irradiation, we produce in this work a unique type of surface nanostructure on Al that have enhanced absorption at UV and visible but a relatively small emissivity in ...infrared. By integrating this laser-treated Al to a solar-driven thermoelectric generator, we show that the thermoelectric generator integrated with the femtosecond laser-treated Al foil generates a significantly higher power than the ones without. Our study shows that our technique can dramatically enhance the efficiency of solar-driven thermoelectric devices that may lead to a leap forward in solar energy harnessing.
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