Ripple formation on Nickel irradiated with radially polarized femtosecond beams

We report on the morphological effects induced by the inhomogeneous absorption of radially polarized femtosecond laser irradiation of nickel (Ni) in sub-ablation conditions. A theoretical prediction of the morphology profile is performed and the role of surface plasmon excitation in the production of self-formed periodic ripples structures is evaluated. Results indicate a smaller periodicity of the ripples profile compared to that attained under linearly polarized irradiation conditions. A combined hydrodynamical and thermoelastic model is presented in laser beam conditions that lead to material melting. The simulation results are presented to be in good agreement with the experimental findings. The ability to control the size of the morphological changes via modulating the beam polarization may provide an additional route for controlling and optimizing the outcome of laser micro-processingComment: 4 pages, 4 figures, 4 appendix page

Influence of Antireflection Si coatings on the Damage Threshold of fused silica upon irradiation with Mid-IR femtosecond laser pulses

Recent progress in the development of high-power mid-IR laser sources and the exciting laser driven physical phenomena associated with the irradiation of solids via ultrashort laser pulses in that spectral region are aimed to potentially create novel capabilities for material processing. In particularly, the investigation of the underlying physical processes and the evaluation of the optical breakdown threshold (OBT) following irradiation of bulk dielectric materials with Mid-IR femtosecond (fs) pulses has been recently presented. In this report, we will explore the conditions that generate sufficient carrier excitation levels which leads to damage upon irradiated a dielectric material (SiO2) coated with antireflection (AR) semiconducting films (Si) of variable thickness with fs pulses. Simulation results demonstrate that the reflectivity and transmissivity of the Si/SiO2 are thickness-dependent which can be employed to modulate the damage threshold of the substrate. The study is to provide innovative routes for selecting material sizes that can be used for antireflection coatings and applications in the Mid-IR region.Comment: TO appear in Optics Letter

Two-dimensional metal halide perovskites and their heterostructures: from synthesis to applications

Size- and shape- dependent unique properties of the metal halide perovskite nanocrystals make them promising building blocks for constructing various electronic and optoelectronic devices. These unique properties together with their easy colloidal synthesis render them efficient nanoscale functional components for multiple applications ranging from light emission devices to energy conversion and storage devices. Recently, two-dimensional (2D) metal halide perovskites in the form of nanosheets (NSs) or nanoplatelets (NPls) are being intensively studied due to their promising 2D geometry which is more compatible with the conventional electronic and optoelectronic device structures where film-like components are employed. In particular, 2D perovskites exhibit unique thickness-dependent properties due to the strong quantum confinement effect, while enabling the bandgap tuning in a wide spectral range. In this review the synthesis procedures of 2D perovskite nanostructures will be summarized, while the application-related properties together with the corresponding applications will be extensively discussed. In addition, perovskite nanocrystals/2D material heterostructures will be reviewed in detail. Finally, the wide application range of the 2D perovskite-based structures developed to date, including pure perovskites and their heterostructures, will be presented while the improved synergetic properties of the multifunctional materials will be discussed in a comprehensive way.Comment: 83 pages, 38 Figure