ARTICLE | doi:10.20944/preprints202212.0583.v1
Subject: Materials Science, Nanotechnology Keywords: light trapping; Si solar cells; ablation; dry etch; Lambertian limit
Online: 30 December 2022 (10:14:28 CET)
Ultra-short 230 fs laser pulses of 515 nm wavelength were tightly focused into 700 nm focal spots and utilised in opening ~ 0.4 − 1 μm holes in alumina Al2O3 etch masks with 20-50 nm thickness. Such dielectric masks simplify fabrication of photonic crystal (PhC) light trapping patterns for the above-Lambertian performance of high efficiency solar cells. Conditions of laser ablation of transparent etch masks and effects sub-surface Si modifications were revealed by plasma etch- ing, numerical modeling, and minority carrier lifetime measurements. Mask-less patterning of Si is proposed using fs-laser direct writing for dry plasma etch of Si.
ARTICLE | doi:10.20944/preprints202005.0416.v1
Subject: Physical Sciences, Astronomy & Astrophysics Keywords: X-rays; free electron laser (FEL); ultra-short phenomena; pump-probe; warm-dense matter; astrophotonics; co-axial volumetric interaction diagnostics
Online: 26 May 2020 (03:53:19 CEST)
We put forward a co-axial pump(optical)-probe(X-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 micrometers-diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-X-ray free electron laser (X-FEL) beam of sub-1 micrometer diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different realisations of optical pump are discussed. Such optical elements facilitate alignment of ultra-short fs-pulses in space and time and can be used in light-matter interaction experiments at extreme energy densities on the surface and in the volume of targets. Full advantage of ultra-short 10 fs X-FEL probe pulses with fs-pump(optical) opens an unexplored temporal dimension of phase transitions and the fastest laser-induced rates of material heating and quenching. A wider field of applications of fs-laser-enabled structuring of materials and design of specific optical elements for astrophotonics is presented.