Free space laser telecommunication through fog

Atmospheric clearness is a key issue for free space optical communications (FSO). We present the first active method to achieve FSO through clouds and fog, using ultrashort high intensity laser filaments. The laser filaments opto-mechanically expel the droplets out of the beam and create a cleared channel for transmitting high bit rate telecom data at 1.55 microns. The low energy required for the process allows considering applications to Earth-satellite FSO and secure ground based optical communication, with classical or quantum protocols.Comment: 4 pages + 2 pages supplementary text and movie

Ultralow‐Power Atomic‐Scale Tin Transistor with Gate Potential in Millivolt

After decades of continuous scaling, further advancement of complementary metal-oxide-semiconductor (CMOS) technology across the entire spectrum of computing applications is today limited by power dissipation, which scales with the square of the supply voltage. Here, an atomic-scale tin transistor is demonstrated to perform conductive switching between bistable configurations with on/off potentials ≤2.5 mV in magnitude. In addition to the low operation voltage, the channel length of the transistor is determined experimentally and with density-functional theory to be ≤1 nm because the atoms instead of electrons are information carriers in this device. The conductance at on-states of the bistable configurations varies between 1.2 G$_{0}$ to 197 G$_{0}$ (G$_{0}$ = 2e$^{2}$ h$^{-1}$, e stands for the electron charge and h for Planck\u27s constant). Thus, the device can supply driving current from 1 to ≈375 µA in magnitude for logic circuits with the drain-source dc voltage at decades of millivolts. The switching frequency of the atomic-scale tin transistor has reached 2047 Hz. Furthermore, the on/off potentials in millivolts can reduce the energy consumption in the interconnects of integrated circuits at least by ≈400 times. Therefore, the atomic-scale tin transistor has prospects in digital circuits with ultralow-power dissipation and can contribute to the sustainability of modern society

Nanoparticle-based tracing techniques in geothermal reservoir: Advances, challenges and prospects

Accurate knowledge of reservoir geometry and flow paths are critical parameters for successful geothermal operations. They are essential for evaluating the long-term behavior and sustainability of geothermal reservoirs. Conventional hydraulic testing and tracer tests are often inconclusive or provide limited information due to complex and challenging reservoir conditions (multiple well systems, complex reservoir geometry, and fracture network, etc.). Recently, a new class of tracer techniques has emerged in order to overcome the major drawbacks of molecular tracers: nanoparticle-based tracers. The main advantages of nanoparticle tracers compared to molecular tracers are their tunable properties and modular structure. Functional and smart nanoparticle tracers such as the threshold-triggered temperature nanotracer enabled the simultaneous evaluation of multiple reservoir conditions (flow paths, temperature distribution, etc.) and created an entirely new field of research. As new areas of research often require detailed insights into fundamental processes, there are still open questions about the interactions between particles, fluids, and rock minerals and their performance in complex geothermal environments. As an example, the application of embedded or surface-bound tracing features (e.g., fluorescent molecules, DNA, etc.) within or on a silica matrix prevents the tracing function from being affected by the environment (e.g., pH changes, salinity effects, redox sensitivity). Although silica has low hydro(thermal) stability and loses its protective function at high temperatures or long-term applications, nanoscience offers a comprehensive set of tools to design and protect the silica matrix. Another advantage is the possibility of surface modifications, which can help to achieve minimum sorption and retention by adapting the ζ-potential of the nanoparticles. In this study, we address recent advances in increasing long-term stability, improving hydrothermal stability of silica nanoparticles, sorption control. Furthermore, we present strategies for the development and functionalization of nanoparticle-based tracers