Full polarization states modulating via an ultra-thin quarter-wave plate

We theoretically and numerically demonstrate a design of an ultra-thin quarter-wave plate (QWP) based on plasmonic metasurface. With the designed QWP, the ellipticity of the output light can be generalized as X $$=$$ 2sin($$\theta )$$cos($$\theta )$$, providing a convenient way to calculate the polarization states of the output light. With such a strategy, output lights with any desired polarization states including linear, circular and especially elliptical can be obtained by adjusting the incident polarization angle $$\theta$$. The Jones vector is adopted to theoretically explore the underlying physics of polarization conversion. Moreover, the finite-difference time-domain (FDTD) simulations are utilized to verify the theoretical results. These results will deepen our understanding of polarization conversion and provide helpful guidelines in designing ultra-thin polarization-dependent devices

Perfect spin filter and strong current polarization in carbon atomic chain with asymmetrical connecting points

The spin-dependent electron transport properties through a single-carbon atomic chain (SCAC) sandwiched between two-zigzag-graphene-nanoribbon (zGNR) electrodes are investigated by performing first-principles calculations based on the nonequilibrium Green's function (NEGF) approach in combination with spin density functional theory (DFT). Our calculations show that SCAC connecting two zGNRs with asymmetry-contacting points is a perfect spin filter in the transmission function within a large energy range. Moreover, the spin-dependent electron transmission spectra exhibit robust transport polarization characteristics and a strong current polarization behavior (almost 100%) can be found. The microscopic mechanisms are proposed for the spin-related phenomena

Thermally tunable THz polarization converter based on Babinet-inverted metasurface

The polarization converters are imperative components in modern optical system, but its functionality is usually statically adjustable due to the constraint of materials. Herein, a Babinet InSb metasurface composed of C-shape resonators is proposed with its anisotropic amplitudes and phases of reflected light along two orthogonal axes can be tailored by adjusting external temperature in the THz range. The simulation results show that designer metasurface is a 90° polarization rotator with the polarization conversion ratio up to 97% at 1.36 THz when temperature T = 298 K. By tuning the external temperature from 280 to 320 K, the polarization conversion functionality can be realized or eliminated near form 1.1 THz to 1.7 THz. The regulation mechanism of the proposed tunable converter is attributed to the electromagnetic coupling pattern between the upper C-shape metasurface and the metallic substrate at different external temperature. The results appear to hold promise for wave retarder devices and modern optical systems

Commissioning of Underground Nuclear Astrophysics Experiment JUNA in China

Underground Nuclear Astrophysics Experiment in China (JUNA) has been commissioned by taking the advantage of the ultra-low background in Jinping underground lab. High current mA level 400 KV accelerator with an ECR source and BGO detectors were commissioned. JUNA studies directly a number of nuclear reactions important to hydrostatic stellar evolution at their relevant stellar energies. In the first quarter of 2021, JUNA performed the direct measurements of 25Mg(p,γ)26Al, 19F(p,α)16O, 13C(α,n)16O and 12C(α,γ)16O near the Gamow window. The experimental results reflect the potential of JUNA with higher statistics, precision and sensitivity of the data. The preliminary results of JUNA experiment and future plan are given