Moiré-driven electromagnetic responses and magic angles in a sandwiched hyperbolic metasurface

Recent moiréconfigurations provide a new platform for tunable and sensitive photonic responses,as their enhanced light–matter interactions originate from the relative displacement or rotation angle in a stacking bilayer or multilayer periodic array.However,previous findings are mostly focused on atomically thin condensed matter,with limitations on the fabrication of multilayer structures and the control of rotation angles.Structured microwave moiréconfigurations are still difficult to realize.Here,we design a novel moiréstructure,which presents unprecedented capability in the manipulation of light–matter interactions.Based on the effective medium theory and S-parameter retrieval process,the rotation matrix is introduced into the dispersion relation to analyze the underlying physical mechanism,where the permittivity tensor transforms from a diagonal matrix to a fully populated one,whereas the permeability tensor evolves from a unit matrix to a diagonal one and finally becomes fully filled,so that the electromagnetic responses change drastically as a result of stacking and rotation.Besides,the experiment and simulation results reveal hybridization of eigenmodes,drastic manipulation of surface states,and magic angle properties by controlling the mutual rotation angles between two isolated layers.Here,not only a more precisely controllable bilayer hyperbolic metasurface is introduced to moiréphysics,the findings also open up a new avenue to realize flat bands at arbitrary frequencies,which shows great potential in active engineering of surface waves and designing multifunctional plasmonic devices.

Organic Memristor Based on High Planar Cyanostilbene/Polymer Composite Films

Organic memristors with low power consumption,fast write/erasure speed,and complementary metal-oxide-semiconductor(CMOS)compatibility have attracted tremendous attention to mimic biological synapses to realize neuromorphic computation in recent years.In this paper,organic resistive switching memory(ORSM)based on(Z)-3-(naphthalen-2-yl)-2-(4-nitrophenyl)acrylonitrile(NNA)and polymer poly(N-vinylcarbazole)(PVK)composite film was prepared by spin-coating method.Device performance based on NNA:PVK composite films with different mass fractions of NNA were systematically investigated.The ORSM based on PVK:40%(mass fraction)NNA composite film exhibited non-volatile and bipolar memory properties with a switching ratio(Ion/Ioff)of 24.1,endurance of 68 times and retention time of 104 s,a“SET”voltage(Vset)of−0.55 V and a“RESET”voltage(Vreset)of 2.35 V.The resistive switching was ascribed to the filling and vacant process of the charge traps induced by NNA and the inherent traps in PVK bulk.The holes trapping and de-trapping process occurred when the device was applied with a negative or positive bias,which caused the transforming of the conductive way of charges,that is the resistive behaviors in the macroscopic.This study provides a promising platform for the fabrication of ORSM with high performance.

Mechanically reprogrammable Pancharatnam-Berry metasurface for microwaves

Metasurfaces have enabled the realization of several optical functionalities over an ultrathin platform,fostering the exciting field of flat optics.Traditional metasurfaces are achieved by arranging a layout of static meta-atoms to imprint a desired operation on the impinging wavefront,but their functionality cannot be altered.Reconfigurability and programmability of metasurfaces are the next important step to broaden their impact,adding customized on-demand functionality in which each meta-atom can be individually reprogrammed.We demonstrate a mechanical metasurface platform with controllable rotation at the meta-atom level,which can implement continuous Pancharatnam–Berry phase control of circularly polarized microwaves.As the proof-of-concept experiments,we demonstrate metalensing,focused vortex beam generation,and holographic imaging in the same metasurface template,exhibiting versatility and superior performance.Such dynamic control of electromagnetic waves using a single,low-cost metasurface paves an avenue towards practical applications,driving the field of reprogrammable intelligent metasurfaces for a variety of applications.