Longitudinal sputtering hollow cathode discharge (HCD) used as active medium for lasing is studied by means of numerical modelling. Due to the longitudinal non-uniformities of the discharge, the laser operation could be strongly affected. The non-uniformity of the discharge is mainly influenced by the dimensions of the hollow cathode, in particular by the aspect ratio length/radius. To study the geometrical features, a simulation model for HCDs has been constructed using the Plasimo modelling platform. The model allows in-depth studies of the plasma mechanisms and enables finding the optimum under the working conditions of the HCDs. The model is validated by comparing the results with the experimental observations. The spatial distribution of the plasma density and potential as well as an in-depth discussion of the results and the trends revealed by the model are presented. The proper understanding of the essential geometrical features allowed defining the optimal aspect ratio length/diameter for stable and uniform discharge with high excitation efficiency.

ELI Beamlines is a rapidly progressing pillar of the pan-European Extreme Light Infrastructure (ELI) project focusing on the development and deployment of science driven by high-power lasers for user operations. This work reports the results of a commissioning run of a water-jet plasma X-ray source driven by the L1 Allegra laser, outlining the current capabilities and future potential of the system. The L1 Allegra is one of the lasers developed in-house at ELI Beamlines, designed to be able to reach a pulse energy of 100 mJ at a 1 kHz repetition rate with excellent beam properties. The water-jet plasma X-ray source driven by this laser opens opportunities for new pump–probe experiments with sub-picosecond temporal resolution and inherent synchronization between pump and probe pulses.

A novel sensor for detection of contaminants in fog using the Surface photo-charge effect is presented. The sensor is capable of measuring the presence of contamination and of giving a relative estimate of its concentration. The sensor uses liquid layer which allows for removing the layer of fog condensation at the solid surface and the signal variation due to fog dynamics density variation. In addition, it is able to measure only the contribution of the fog admixtures to the Surface photocharge effect signal.

Silk fibroin (SF), the primary protein in silkworm silk, has emerged as a promising organic nonlinear optical material due to its unique combination of optical transparency, biocompatibility, and environmental sustainability. In this study, we investigate the nonlinear optical properties of SF thin films using the z-scan technique with femtosecond laser pulses (35 fs, 800 nm, 1 kHz). Our results reveal a strong self-defocusing effect (negative nonlinear refractive index) and significant multiphoton absorption, demonstrating SF’s tunable nonlinear response. Additionally, optical transmittance measurements confirm SF’s partial transparency in the deep UV region, enhancing its potential for second-harmonic generation (SHG) and efficient light frequency conversion. These findings address a key knowledge gap in nonlinear optics, positioning SF as a versatile biopolymer for advanced photonic applications.