arXiv subjects

Panagiotis Lingos

Publications and source records attributed to Panagiotis Lingos.

3 recordsLinked to original sources

arXiv2023

Impact of plasmonic modes on the formation of self-organised nano-patterns in thin films

Formation of nanoscale laser-induced periodic surface structures on thin metal films (of the size of the optical penetration depth) is a yet unexplored area that is expected to open new routes for laser patterning and a wealth of exciting applications in optics, photonics, and sensing. In contrast to the common belief that excitation of Surface Plasmon Polaritons (SPPs) on the air/metal interface plays the dominant role in the features of the induced topographies, in this work, we demonstrate that the excitation of coupled SPPs in both air/metal and metal/substrate interfaces, along with other parameters such as the thickness of the material, the photon energy, and the substrate refractive index, dictate the spatial modulation of the absorbed energy. A detailed theoretical analysis of the excited plasmonic waves and a multiscale modelling of laser-induced physical phenomena manifests that depending on the laser conditions and thickness of the irradiated solid, topographies with periodic features of diverse sizes (ranging from $λ_L/3$ to $λ_L$, where $λ_L$ stands for the laser wavelength) and different orientation can be realized. The capability to control and tune the characteristics of the produced structures on thin films is expected to enable novel surface patterning approaches.

physics.optics↗

arXiv2023

Highly ordered LIPSS on Au thin film for plasmonic sensing fabricated by double femtosecond pulses

Periodic plasmonic arrays making possible excitations of surface lattice resonances (SLRs) or quasi-resonant features are of great importance for biosensing and other applications. Fabrication of such arrays over a large area is typically very costly and time-consuming when performed using conventional electron beam lithography and other methods, which reduce application prospects. Here, we propose a technique of double femtosecond pulse (~ 170 fs) laser-assisted structuring of thin (~ 32 nm) Au films deposited on a glass substrate and report a single-step fabrication of homogeneous and highly ordered Au-based Laser Induced Periodic Surface Structures (LIPSS) over a large area. Our experimental results unveil the key importance of the interpulse delay as the determining factor rendering possible the homogeneity of laser induced structures and confirm that highly ordered, functional LIPSS occur solely upon double pulse irradiation under a specific interpulse delay range. A theoretical investigation complements experimental results providing remarkable insights on the structure formation mechanism. Ellipsometric measurements show that such LIPSS structures can exhibit highly valuable plasmonic features in light reflection. In particular, we observed ultranarrow resonances associated with diffraction-coupled SLRs, which are of paramount importance for biosensing and other applications. The presented data suggest that femtosecond double pulse structuring of thin metal films can serve as a valuable and low-cost tool for a large-scale fabrication of highly ordered functional elements and structures.

cond-mat.mtrl-sci↗

arXiv2022

The synergy of electromagnetic effects and thermophysical properties of metals in the formation of laser induced periodic surface structures

Femtosecond pulsed lasers have been widely used over the past decades for precise materials structuring at the micro- and nano- scales. In order, though, to realize efficient material processing and account for the formation of laser induced periodic surfaces structures (LIPSS), it is very important to understand the fundamental laser-matter interaction processes. A significant contribution to the LIPSS profile appears to originate from the electromagnetic fingerprint of the laser source. In this work, we follow a systematic approach to predict the pulse-by-pulse formation of LIPSS on metals due to the development of a spatially periodic energy deposition that results from the interference of electromagnetic far fields on a non-flat surface profile. On the other hand, we demonstrate that the induced electromagnetic effects, alone, are not sufficient to allow the LIPSS formation, therefore, we emphasize on the crucial role of electron diffusion and electron-phonon coupling on the formation of stable periodic structures. Gold and stainless Steel are considered as two materials to test the theoretical model while simulation results appear to confirm the experimental results that, unlike gold, fabrication of pronounced LIPSS on stainless Steel is feasible.

physics.optics↗