Triggering rain on demand is an old dream of mankind, with a huge potential socio-economical benefit. To date, efforts have mainly focused on cloud-seeding using silver salt particles. We demonstrate that self-guided ionized filaments generated by ultrashort laser pulses are also able to induce water-cloud condensation in the free, sub-saturated atmosphere. Potential contributing mechanisms include photo-oxidative chemistry and electrostatic effects. As well as revealing the potential for influencing or triggering water precipitation, laser-induced water condensation provides a new tool for the remote sensing of nucleation processes in clouds

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Three‐dimensional patterning of metal–dielectric composites is achieved at the sub‐micrometer scale in glass. A high silver‐content zinc‐phosphate optical transparent glass is structured by means of a near‐infrared femtosecond laser via non‐linear absorption processes. The silver ions embedded in glass photochemically react under controlled laser irradiation, inducing ion clustering and the formation of nucleation centers. A subsequent thermal development causes silver reduction and growth into metallic nanoparticles. A very strong surface plasmon resonance is measured, revealing the very high concentration of metallic particles. The direct laser writing process enables inscriptions of silver nanoparticle domains well below the diffraction limit (∼100 nm). A very detailed parametric study is given, leading to the first thorough understanding of the ultrafast laser‐induced photochemistry in silver‐containing glass materials. These nanostructures are considered promising candidates for the design of highly efficient sensing devices via plasmonics and, beyond that, for photonics and metamaterials applications.

We have experimentally measured that laser filaments in air generate up to 1014, 3×1012, and 3×1013 molecules of O3, NO, and NO2, respectively. The corresponding local concentrations in the filament active volume are 1016, 3×1014, and 3×1015 cm−3, and allows efficient oxidative chemistry of nitrogen, resulting in concentrations of HNO3 in the parts per million range. The latter forming binary clusters with water, our results provide a plausible pathway for the efficient nucleation recently observed in laser filaments