Terahertz control of air lasing

The coherent emission from ionized nitrogen molecules is of interest for remote sensing and astronomical applications. To initiate the lasing process, we used an intense ultrashort near-infrared (NIR) pulse overlapped with a terahertz (THz) single-cycle pulse. We observed that coherent emission could be seeded and modulated by the amplitude of the THz field, which is the result of a combined effective second-order nonlinear polarization and the nonlinear effects induced by the NIR pump. Our results shed light on the role of intense transient fields in the coherent emission from photoexcited gas molecules

Europe’s Rhine power: connections, borders, and flows

This article explores the pivotal position of the river Rhine in the gradual development of a European electricity system. Although the general image of the Rhine is one of a inland transport corridor, it also acted as a backbone of electricity supply systems since the dawn of the 20th century. By relying on insights from both water history and history of technology, the article argues for a transnational approach to better?grasp the dynamics of river use and related electricity generation, which often went below, as well as above and beyond nation-state affairs