Formation Of Laser-induced Periodic Structures Research Articles

Formation of Laser-Induced Periodic Structures on Thin Films of Transition Metal and Semiconductor Nitrides

Formation of Laser-Induced Periodic Structures on Thin Films of Transition Metal and Semiconductor Nitrides

Laser-induced periodic surface structuring for secondary electron yield reduction of copper: dependence on ambient gas and wavelength

One of the main limitations for future high-performance accelerators operating with positively charged particles is the formation of an electron-cloud inside the beam vacuum chamber, giving rise to instabilities. The Secondary Electron Yield (SEY) of the beam-facing surfaces gives a measure of the mechanism which drives this phenomenon. The laser-induced periodic structure formation on Cu surfaces has been demonstrated as a promising process to reduce SEY. In view of applications in beam chambers, we studied the laser process influence on SEY for 515 and 1030 nm wavelength femtosecond pulses on copper in different ambiences (air, nitrogen, vacuum). Depending on used process conditions, the surface composition differs, structures with varying aspect ratio are formed, i.e., periodic ripples and large-scale channels. Treatment in air at 515 nm is the most efficient for the formation of deeper structures allowing SEY maximum reduction first down to 1.6–1.7 and then below unity upon electron irradiation, thereby totally suppressing electron-cloud. Increasing the laser fluence, SEY will further reduce due to surface roughness enhancement via nanoparticle redeposition. This study reveals the fundamental role of LIPSS treatments to enable surface treatment in large-scale accelerator installations, where particle-free components are desired, and paves the way to potential future applications.

Ionization dynamics and damage conditions in fused silica irradiated with mid-infrared femtosecond pulses

The employment of ultrashort laser sources at the mid-infrared (mid-IR) spectral region for dielectrics is expected to open innovative routes for laser patterning and a wealth of exciting applications in optics and photonics. To elucidate the material response to irradiation with mid-IR laser sources, a consistent analysis of the interaction of long wavelength femtosecond pulses with dielectric materials is presented. The influence of the pulse duration is particularly emphasized in specifying the laser parameters for which photoionization and impact ionization are important. Simulation results using pulses at 2.2, 3.2, and 5 μm are conducted to illustrate optimum conditions for the onset of damage on the solid that is related to the occurrence of the optical breakdown. The results predict that the damage threshold scales as ∼τpa (0.31≤a≤0.37) at all laser wavelengths. Given the significant effect of the induced excitation level on excitation of surface plasmons (SPs), which account for the formation of laser-induced periodic structures oriented perpendicular to the laser polarization, a correlation of the produced electron densities with SPs and the threshold of SP excitation (∼τpβ, 0.33≤β≤0.39) are also discussed in this as yet unexplored spectral region. The results are expected to guide development of an innovative approach to surface patterning using strong mid-IR pulses for advanced applications.

Formation of laser-induced periodic structures on thin films of transition metal nitrides

Formation of laser-induced periodic structures on thin films of transition metal nitrides

Laser-induced periodic structure formation in AlN ceramic

In this work, we show that nanosecond laser processing of aluminium nitride (AlN) ceramic by a Nd:YAG laser operated at the fundamental wavelength (1064 nm) leads to the formation of a conductive layer decorated by a ripples structure. The characteristic orientation of these structures is perpendicular to the incident laser polarization. The period of the ripples is lower than the laser wavelength, namely, about 830 nm. Such structuring is observed after processing both in air and in vacuum. We discuss the mechanism of periodic structures formation based on the dependence of the surface morphology on the laser pulse number and fluence applied and the results of a simulation using the finite-difference time-domain approach. These results can form the basis of fabricating aluminium micro- and nanostructures with potential applications in electronics and photonics as systems for UV plasmonics.

Nanostructuring of Fe73.5Nb3Cu1Si15.5B7 amorphous alloy surface by laser-induced periodic structure formation

Nanostructuring of Fe73.5Nb3Cu1Si15.5B7 amorphous alloy surface by laser-induced periodic structure formation

Femtosecond laser-induced line structuring on mold stainless steel STAVAX with various scanning speeds and two polarization configurations

A femtosecond laser has been used to produce spatially confined micromachining on mold stainless steel STAVAX. We investigated femtosecond laser-induced line structuring on mold stainless steel STAVAX using the laser scanning mode with various scanning speeds, various fluences and two polarization configurations. The damage threshold fluence of single pulse irradiation (Fth) was measured to be about 80 mJ/cm2. The damage threshold fluence of the scanning mode was approximately identical (0.75 Fth∼1.25 Fth) to that of the single pulse irradiation. However, a fluence of 2.50 Fth was necessary to induce continuous line structures for high scanning speeds and a fluence of 1.25 Fth was required to induce continuous line structures for low scanning speeds. The width of laser-machined lines increased with the irradiation fluence and decreased with the scanning speed regardless of the polarization configuration. The formation of laser-induced periodic structures (termed “ripple”) was examined using various laser parameters. It was clear that the formation of the ripple was governed by the irradiation fluence and the scanning speed of the beam. We were able to produce nano-scale structures in large areas by employing multiple line irradiations with the laser beam.

Laser‐induced periodic surface structure on a polymer surface: The effect of a prerubbing treatment on the surface structure

AbstractThe influence of the mechanical rubbing of a polyimide (PI) film on the laser‐induced periodic structure (LIPS) was demonstrated. The periodicity and amplitude of LIPS were greater when the rubbing direction was parallel to the laser polarization direction. The amplitude became small and the periodicity of LIPS did not show an obvious change when the rubbing direction was perpendicular to the laser polarization direction. The effect of the rubbing pretreatment on LIPS was explained on the basis of the wave‐guide effect of rubbing‐induced microgrooves on LIPS formation. The orientation of PI chains induced by mechanical rubbing was relaxed after laser irradiation, and a new orientation of PI chains was formed during the LIPS formation. When the rubbing direction was perpendicular to the laser polarization direction, the orientation of PI chains remained in the rubbing direction. The laser‐irradiated, perpendicularly rubbed PI surface could be used to verify the effects of surface morphologies and intermolecular interactions on liquid‐crystal alignment. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1273–1280, 2003

Laser-induced periodic surface structure on polyimide doped with lecithin

The doping effect of lecithin molecules on the formation of laser-induced periodic structure (LIPS) was investigated. The lecithin dopant can decrease the threshold energy of LIPS formation on polyimde (PI) surface, but the LIPS becomes inconsistent and a lot of break line appeared along the LIPS structure when the doping level is up to 30%. The lecithin-doped PI film forms regular LIPS easier when it is irradiated at 266-nm laser beam than at 355-nm laser beam. FT-IR and contact angle results show that the lecithin molecules migrate to the film surface after laser irradiation.