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Designing perfect anomalous reflectors is crucial for achieving many metasurface-based applications, but available design approaches for the cases of extremely large bending angles either require unrealistic gain–loss materials or rely on brute-force optimizations lacking physical guidance. Here, we propose a deterministic approach to design passive metasurfaces that can reflect impinging light to arbitrary nonspecular directions with almost 100% efficiencies. With both incident and out-going far-field waves given, we can retrieve the surface-impedance profile of the target metadevice by matching boundary conditions with all allowed near-field modes added self-consistently and then construct the metadevices deterministically based on passive meta-atoms exhibiting local responses. We design/fabricate two proof-of-concept microwave metadevices and experimentally demonstrate that the first one achieves anomalous reflection to a 70° angle with efficiency ∼98%, and the second one can generate multiple reflected beams with desired bending angles and power allocations. Our findings pave the way for realizing high-efficiency wave-control metadevices with desired functionalities.

Core-shell structured particles have been used to toughen brittle polylactide (PLA) extensively. In this research, reactive core-shell (RCS) particles with polybutadiene (PB) as core and the terpolymer styrene-acrylonitrile-glycidyl methacrylate as shell were prepared to improve the toughening ability of RCS for PLA. The tert-dodecyl mercaptan (TDDM) content was varied during polymerization and higher TDDM concentrations induced lower grafting and cross-linking of the PB phase, which significantly influenced the dispersed phase morphology and toughness of RCS toughened PLA blends. With the increase of TDDM content, the phase morphology of RCS changed from uniform dispersion, net-like structure to an agglomeration pattern. The impact strength of PLA blends increased with TDDM content and reached 922 J/m for the PLA/RCS-T5 (TDDM: 1.18 wt%), which was 30 times higher than pristine PLA and ~3 times than PLA/RCS-[T.sub.0] blend. Higher TDDM contents decreased toughening efficiency. Appropriate TDDM contents decreased the glass transition temperature ([T.sub.g]) and cross-linking degree of RCS particles which enhanced the cavitation ability of the PB core phase and promoted the shear yielding of PLA matrix. The modification effect of TDDM solves the problem of insufficient toughening ability of core-shell particles. Under the same toughener content, the modified RCS particles make the PLA blend achieve super toughness. KEYWORDS polylactide, reactive core-shell particle, TDDM modification, toughening, 1 | INTRODUCTION Polylactide (PLA) is an important biodegradable thermoplastic polymer. It has attracted extensive attention in recent years because of its excellent mechanical strength, easy processability, complete biodegradability, and [...]

In this work, electron beam irradiation technology was used to increase the dielectric and energy storage performance of polypropylene (PP) films. Electron beam irradiation makes no difference on the crystal morphology but decreased the crystallinity and crystal size of PP. Besides, irradiation improved the thermal stability and polarity of PP. The irradiated PP films behaved much higher dielectric constant than pure PP films. Actually, the dielectric constant of the irradiated PP with 30 kGy was 3.98, while the dielectric constant of pristine PP was only 2.8. Furthermore, the irradiated PP films still kept low dielectric loss and AC conductivity. Weibull distribution test results proved electron beam irradiation improved the breakdown strength of PP films. The discharged energy storage of PP films increased from 1.3 J/[cm.sup.3] of pristine PP film to 3.6 J/[cm.sup.3] of irradiated PP with 30 kGy film. Moreover, the PP film irradiated with 30 kGy displayed an excellent charge-discharge efficiency of more than 95%. This research provides an easy and practical approach to investigate dielectric PP material for energy storage. KEYWORDS dielectric properties, electron beam irradiation, energy storage, polypropylene, 1 | INTRODUCTION Capacitors play critical roles in various fields such as aerospace, military, telecommunications, electronics, and power in the form of electronic components. [1] The characteristics of capacitors depend [...]

Achieving a pre-designed scattering pattern from an ultra-compact platform is highly desired for on-chip integration optics, but conventional techniques suffer from the limitations of bulky size, wavelength-scale modulation and low efficiency. Here, we propose a new strategy to efficiently generate arbitrary spin-polarized scattering far-field patterns from surface-wave (SW) excitations on a designer Pancharatnam–Berry (PB) metasurface. We find that a PB meta-atom serves as a subwavelength scatter to decouple impinging SW to a spin-polarized propagating wave (PW) with tailored amplitude and phase, and thus interference among PWs generated by scatterings at different PB meta-atoms can generate a tailored far-field pattern. As a proof of concept, we design and fabricate a series of PB metasurfaces in the microwave regime and experimentally demonstrate that they can generate desired radiation patterns within a broad frequency band, including unidirectional radiation, line/point focusing, vortex beam and hologram. These findings may stimulate important applications in on-chip integrated photonics.

Delaying an electromagnetic (EM) wave pulse on a thin screen for a significant time before releasing it is highly desired in many applications, such as optical camouflage, information storage, and wave–matter interaction boosting. However, available approaches to achieve this goal either require thick and complex systems or suffer from low efficiencies and a short delay time. This paper proposes an ultra-thin meta-platform that can significantly delay an EM-wave pulse after reflection. Specifically, our meta-platform consists of three meta-surfaces integrated together, of which two are responsible for efficiently coupling incident EM-wave pulse into surface waves (SWs) and vice versa, and the third one supports SWs exhibiting significantly reduced group velocity. We employ theoretical model analyses, full-wave simulations, and microwave experiments to validate the proposed concept. Our experiments demonstrate a 13 ns delay of an EM pulse centered at 12.975 GHz, enabled by a λ/8-thick and 38-λ-long meta-device with an efficiency of 32% (or 70%) with (or without) material loss taken into account. A larger delay time can be enabled by devices with larger sizes considering that the SWs group velocity of our device can be further reduced via dispersion engineering. These findings establish a new road for delaying an EM-wave pulse with ultra-thin screens, which may lead to many promising applications in integration optics. [ABSTRACT FROM AUTHOR]